cmsis_dap.c

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// SPDX-License-Identifier: GPL-2.0-or-later
 
/***************************************************************************
 *   Copyright (C) 2021 by Adrian Negreanu                                 *
 *   groleo@gmail.com                                                      *
 *                                                                         *
 *   Copyright (C) 2018 by Mickaël Thomas                                  *
 *   mickael9@gmail.com                                                    *
 *                                                                         *
 *   Copyright (C) 2016 by Maksym Hilliaka                                 *
 *   oter@frozen-team.com                                                  *
 *                                                                         *
 *   Copyright (C) 2016 by Phillip Pearson                                 *
 *   pp@myelin.co.nz                                                       *
 *                                                                         *
 *   Copyright (C) 2014 by Paul Fertser                                    *
 *   fercerpav@gmail.com                                                   *
 *                                                                         *
 *   Copyright (C) 2013 by mike brown                                      *
 *   mike@theshedworks.org.uk                                              *
 *                                                                         *
 *   Copyright (C) 2013 by Spencer Oliver                                  *
 *   spen@spen-soft.co.uk                                                  *
 ***************************************************************************/
 
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
 
#include <transport/transport.h>
#include "helper/replacements.h"
#include <jtag/adapter.h>
#include <jtag/swd.h>
#include <jtag/interface.h>
#include <jtag/commands.h>
#include <jtag/tcl.h>
#include <target/cortex_m.h>
 
#include "cmsis_dap.h"
#include "libusb_helper.h"
 
/* Create a dummy backend for 'backend' command if real one does not build */
#if BUILD_CMSIS_DAP_USB == 0
const struct cmsis_dap_backend cmsis_dap_usb_backend = {
    .name = "usb_bulk",
};
#endif
 
#if BUILD_CMSIS_DAP_HID == 0
const struct cmsis_dap_backend cmsis_dap_hid_backend = {
    .name = "hid"
};
#endif
 
#if BUILD_CMSIS_DAP_TCP == 0
const struct cmsis_dap_backend cmsis_dap_tcp_backend = {
    .name = "tcp"
};
#endif
 
static const struct cmsis_dap_backend *const cmsis_dap_backends[] = {
    &cmsis_dap_usb_backend,
    &cmsis_dap_hid_backend,
    &cmsis_dap_tcp_backend,
};
 
/* USB Config */
 
/* Known vid/pid pairs:
 * VID 0xc251: Keil Software
 * PID 0xf001: LPC-Link-II CMSIS_DAP
 * PID 0xf002: OPEN-SDA CMSIS_DAP (Freedom Board)
 * PID 0x2722: Keil ULINK2 CMSIS-DAP
 * PID 0x2750: Keil ULINKplus CMSIS-DAP
 *
 * VID 0x0d28: mbed Software
 * PID 0x0204: MBED CMSIS-DAP
 */
 
#define MAX_USB_IDS 8
/* vid = pid = 0 marks the end of the list */
static uint16_t cmsis_dap_vid[MAX_USB_IDS + 1] = { 0 };
static uint16_t cmsis_dap_pid[MAX_USB_IDS + 1] = { 0 };
static int cmsis_dap_backend = -1;
static bool swd_mode;
static bool cmsis_dap_quirk_mode;  /* enable expensive workarounds */
 
/* CMSIS-DAP General Commands */
#define CMD_DAP_INFO              0x00
#define CMD_DAP_LED               0x01
#define CMD_DAP_CONNECT           0x02
#define CMD_DAP_DISCONNECT        0x03
#define CMD_DAP_WRITE_ABORT       0x08
#define CMD_DAP_DELAY             0x09
#define CMD_DAP_RESET_TARGET      0x0A
 
/* CMD_INFO */
#define INFO_ID_VENDOR            0x01      /* string */
#define INFO_ID_PRODUCT           0x02      /* string */
#define INFO_ID_SERNUM            0x03      /* string */
#define INFO_ID_FW_VER            0x04      /* string */
#define INFO_ID_TD_VEND           0x05      /* string */
#define INFO_ID_TD_NAME           0x06      /* string */
#define INFO_ID_CAPS              0xf0      /* byte */
#define INFO_ID_PKT_CNT           0xfe      /* byte */
#define INFO_ID_PKT_SZ            0xff      /* short */
#define INFO_ID_SWO_BUF_SZ        0xfd      /* word */
 
#define INFO_CAPS_SWD                 BIT(0)
#define INFO_CAPS_JTAG                BIT(1)
#define INFO_CAPS_SWO_UART            BIT(2)
#define INFO_CAPS_SWO_MANCHESTER      BIT(3)
#define INFO_CAPS_ATOMIC_CMDS         BIT(4)
#define INFO_CAPS_TEST_DOMAIN_TIMER   BIT(5)
#define INFO_CAPS_SWO_STREAMING_TRACE BIT(6)
#define INFO_CAPS_UART_PORT           BIT(7)
#define INFO_CAPS_USB_COM_PORT        BIT(8)
#define INFO_CAPS__NUM_CAPS               9
 
/* CMD_LED */
#define LED_ID_CONNECT            0x00
#define LED_ID_RUN                0x01
 
#define LED_OFF                   0x00
#define LED_ON                    0x01
 
/* CMD_CONNECT */
#define CONNECT_DEFAULT           0x00
#define CONNECT_SWD               0x01
#define CONNECT_JTAG              0x02
 
/* CMSIS-DAP Common SWD/JTAG Commands */
#define CMD_DAP_DELAY             0x09
#define CMD_DAP_SWJ_PINS          0x10
#define CMD_DAP_SWJ_CLOCK         0x11
#define CMD_DAP_SWJ_SEQ           0x12
 
/*
 * PINS
 * Bit 0: SWCLK/TCK
 * Bit 1: SWDIO/TMS
 * Bit 2: TDI
 * Bit 3: TDO
 * Bit 5: nTRST
 * Bit 7: nRESET
 */
 
#define SWJ_PIN_TCK               (1<<0)
#define SWJ_PIN_TMS               (1<<1)
#define SWJ_PIN_TDI               (1<<2)
#define SWJ_PIN_TDO               (1<<3)
#define SWJ_PIN_TRST              (1<<5)
#define SWJ_PIN_SRST              (1<<7)
 
/* CMSIS-DAP SWD Commands */
#define CMD_DAP_SWD_CONFIGURE     0x13
#define CMD_DAP_SWD_SEQUENCE      0x1D
 
/* CMSIS-DAP JTAG Commands */
#define CMD_DAP_JTAG_SEQ          0x14
#define CMD_DAP_JTAG_CONFIGURE    0x15
#define CMD_DAP_JTAG_IDCODE       0x16
 
/* CMSIS-DAP JTAG sequence info masks */
/* Number of bits to clock through (0 means 64) */
#define DAP_JTAG_SEQ_TCK          0x3F
/* TMS will be set during the sequence if this bit is set */
#define DAP_JTAG_SEQ_TMS          0x40
/* TDO output will be captured if this bit is set */
#define DAP_JTAG_SEQ_TDO          0x80
 
 
/* CMSIS-DAP Transfer Commands */
#define CMD_DAP_TFER_CONFIGURE    0x04
#define CMD_DAP_TFER              0x05
#define CMD_DAP_TFER_BLOCK        0x06
#define CMD_DAP_TFER_ABORT        0x07
 
/* DAP_TransferBlock increases the sum of command/response sizes
 * (due to 16-bit Transfer Count) if used in a small packet.
 * Prevent using it until we have at least r/w operations. */
#define CMD_DAP_TFER_BLOCK_MIN_OPS 4
 
/* DAP Status Code */
#define DAP_OK                    0
#define DAP_ERROR                 0xFF
 
/* CMSIS-DAP SWO Commands */
#define CMD_DAP_SWO_TRANSPORT     0x17
#define CMD_DAP_SWO_MODE          0x18
#define CMD_DAP_SWO_BAUDRATE      0x19
#define CMD_DAP_SWO_CONTROL       0x1A
#define CMD_DAP_SWO_STATUS        0x1B
#define CMD_DAP_SWO_DATA          0x1C
#define CMD_DAP_SWO_EX_STATUS     0x1E
 
/* SWO transport mode for reading trace data */
#define DAP_SWO_TRANSPORT_NONE    0
#define DAP_SWO_TRANSPORT_DATA    1
#define DAP_SWO_TRANSPORT_WINUSB  2
 
/* SWO trace capture mode */
#define DAP_SWO_MODE_OFF          0
#define DAP_SWO_MODE_UART         1
#define DAP_SWO_MODE_MANCHESTER   2
 
/* SWO trace data capture */
#define DAP_SWO_CONTROL_STOP      0
#define DAP_SWO_CONTROL_START     1
 
/* SWO trace status */
#define DAP_SWO_STATUS_CAPTURE_INACTIVE      0
#define DAP_SWO_STATUS_CAPTURE_ACTIVE        1
#define DAP_SWO_STATUS_CAPTURE_MASK          BIT(0)
#define DAP_SWO_STATUS_STREAM_ERROR_MASK     BIT(6)
#define DAP_SWO_STATUS_BUFFER_OVERRUN_MASK   BIT(7)
 
/* CMSIS-DAP Vendor Commands
 * None as yet... */
 
static const char * const info_caps_str[INFO_CAPS__NUM_CAPS] = {
    "SWD supported",
    "JTAG supported",
    "SWO-UART supported",
    "SWO-MANCHESTER supported",
    "Atomic commands supported",
    "Test domain timer supported",
    "SWO streaming trace supported",
    "UART communication port supported",
    "UART via USB COM port supported",
};
 
struct pending_scan_result {
    unsigned int first;
    unsigned int length;
    uint8_t *buffer;
    unsigned int buffer_offset;
};
 
/* Each block in FIFO can contain up to pending_queue_len transfers */
static unsigned int pending_queue_len;
static unsigned int tfer_max_command_size;
static unsigned int tfer_max_response_size;
 
/* pointers to buffers that will receive jtag scan results on the next flush */
#define MAX_PENDING_SCAN_RESULTS 256
static int pending_scan_result_count;
static struct pending_scan_result pending_scan_results[MAX_PENDING_SCAN_RESULTS];
 
/* queued JTAG sequences that will be executed on the next flush */
#define QUEUED_SEQ_BUF_LEN (cmsis_dap_handle->packet_usable_size - 3)
static int queued_seq_count;
static int queued_seq_buf_end;
static int queued_seq_tdo_ptr;
static uint8_t queued_seq_buf[1024]; /* TODO: make dynamic / move into cmsis object */
 
static int queued_retval;
 
static uint8_t output_pins = SWJ_PIN_SRST | SWJ_PIN_TRST;
 
static struct cmsis_dap *cmsis_dap_handle;
 
 
static int cmsis_dap_quit(void);
 
static int cmsis_dap_open(void)
{
    const struct cmsis_dap_backend *backend = NULL;
 
    struct cmsis_dap *dap = calloc(1, sizeof(struct cmsis_dap));
    if (!dap) {
        LOG_ERROR("unable to allocate memory");
        return ERROR_FAIL;
    }
 
    int retval = ERROR_FAIL;
    if (cmsis_dap_backend >= 0) {
        /* Use forced backend */
        backend = cmsis_dap_backends[cmsis_dap_backend];
        if (backend->open)
            retval = backend->open(dap, cmsis_dap_vid, cmsis_dap_pid, adapter_get_required_serial());
        else
            LOG_ERROR("Requested CMSIS-DAP backend is disabled by configure");
 
    } else {
        /* Try all backends */
        for (unsigned int i = 0; i < ARRAY_SIZE(cmsis_dap_backends); i++) {
            backend = cmsis_dap_backends[i];
            if (!backend->open)
                continue;
 
            retval = backend->open(dap, cmsis_dap_vid, cmsis_dap_pid, adapter_get_required_serial());
            if (retval == ERROR_OK)
                break;
        }
    }
 
    if (retval != ERROR_OK) {
        LOG_ERROR("unable to find a matching CMSIS-DAP device");
        free(dap);
        return retval;
    }
 
    dap->backend = backend;
 
    cmsis_dap_handle = dap;
 
    return ERROR_OK;
}
 
static void cmsis_dap_close(struct cmsis_dap *dap)
{
    if (dap->backend) {
        if (dap->backend->close)
            dap->backend->close(dap);
        dap->backend = NULL;
    }
 
    free(dap->packet_buffer);
 
    for (unsigned int i = 0; i < MAX_PENDING_REQUESTS; i++) {
        free(dap->pending_fifo[i].transfers);
        dap->pending_fifo[i].transfers = NULL;
    }
 
    free(cmsis_dap_handle);
    cmsis_dap_handle = NULL;
}
 
static void cmsis_dap_flush_read(struct cmsis_dap *dap)
{
    unsigned int i;
    /* Some CMSIS-DAP adapters keep buffered packets over
     * USB close/open so we need to flush up to 64 old packets
     * to be sure all buffers are empty */
    for (i = 0; i < 64; i++) {
        int retval = dap->backend->read(dap, 10, CMSIS_DAP_BLOCKING);
        if (retval == ERROR_TIMEOUT_REACHED)
            break;
    }
    if (i)
        LOG_DEBUG("Flushed %u packets", i);
}
 
/* Send a message and receive the reply */
static int cmsis_dap_xfer(struct cmsis_dap *dap, int txlen)
{
    if (dap->write_count + dap->read_count) {
        LOG_ERROR("internal: queue not empty before xfer");
    }
    if (dap->pending_fifo_block_count) {
        LOG_ERROR("pending %u blocks, flushing", dap->pending_fifo_block_count);
        while (dap->pending_fifo_block_count) {
            dap->backend->read(dap, 10, CMSIS_DAP_BLOCKING);
            dap->pending_fifo_block_count--;
        }
        dap->pending_fifo_put_idx = 0;
        dap->pending_fifo_get_idx = 0;
    }
 
    uint8_t current_cmd = dap->command[0];
    int retval = dap->backend->write(dap, txlen, LIBUSB_TIMEOUT_MS);
    if (retval < 0)
        return retval;
 
    /* get reply */
    retval = dap->backend->read(dap, LIBUSB_TIMEOUT_MS, CMSIS_DAP_BLOCKING);
    if (retval < 0)
        return retval;
 
    uint8_t *resp = dap->response;
    if (resp[0] == DAP_ERROR) {
        LOG_ERROR("CMSIS-DAP command 0x%" PRIx8 " not implemented", current_cmd);
        return ERROR_NOT_IMPLEMENTED;
    }
 
    if (resp[0] != current_cmd) {
        LOG_ERROR("CMSIS-DAP command mismatch. Sent 0x%" PRIx8
             " received 0x%" PRIx8, current_cmd, resp[0]);
 
        dap->backend->cancel_all(dap);
        cmsis_dap_flush_read(dap);
        return ERROR_FAIL;
    }
 
    return ERROR_OK;
}
 
static int cmsis_dap_cmd_dap_swj_pins(uint8_t pins, uint8_t mask, uint32_t delay, uint8_t *input)
{
    uint8_t *command = cmsis_dap_handle->command;
 
    command[0] = CMD_DAP_SWJ_PINS;
    command[1] = pins;
    command[2] = mask;
    h_u32_to_le(&command[3], delay);
 
    int retval = cmsis_dap_xfer(cmsis_dap_handle, 7);
    if (retval != ERROR_OK) {
        LOG_ERROR("CMSIS-DAP command CMD_DAP_SWJ_PINS failed.");
        return ERROR_JTAG_DEVICE_ERROR;
    }
 
    if (input)
        *input = cmsis_dap_handle->response[1];
 
    return ERROR_OK;
}
 
static int cmsis_dap_cmd_dap_swj_clock(uint32_t swj_clock)
{
    uint8_t *command = cmsis_dap_handle->command;
 
    /* set clock in Hz */
    swj_clock *= 1000;
 
    command[0] = CMD_DAP_SWJ_CLOCK;
    h_u32_to_le(&command[1], swj_clock);
 
    int retval = cmsis_dap_xfer(cmsis_dap_handle, 5);
    if (retval != ERROR_OK || cmsis_dap_handle->response[1] != DAP_OK) {
        LOG_ERROR("CMSIS-DAP command CMD_DAP_SWJ_CLOCK failed.");
        return ERROR_JTAG_DEVICE_ERROR;
    }
 
    return ERROR_OK;
}
 
/* clock a sequence of bits out on TMS, to change JTAG states */
static int cmsis_dap_cmd_dap_swj_sequence(uint8_t s_len, const uint8_t *sequence)
{
    uint8_t *command = cmsis_dap_handle->command;
 
#ifdef CMSIS_DAP_JTAG_DEBUG
    LOG_DEBUG("cmsis-dap TMS sequence: len=%d", s_len);
    for (unsigned int i = 0; i < DIV_ROUND_UP(s_len, 8); ++i)
        printf("%02X ", sequence[i]);
 
    printf("\n");
#endif
 
    command[0] = CMD_DAP_SWJ_SEQ;
    command[1] = s_len;
    bit_copy(&command[2], 0, sequence, 0, s_len);
 
    int retval = cmsis_dap_xfer(cmsis_dap_handle, 2 + DIV_ROUND_UP(s_len, 8));
    if (retval != ERROR_OK || cmsis_dap_handle->response[1] != DAP_OK)
        return ERROR_FAIL;
 
    return ERROR_OK;
}
 
static int cmsis_dap_cmd_dap_info(uint8_t info, uint8_t **data)
{
    uint8_t *command = cmsis_dap_handle->command;
 
    command[0] = CMD_DAP_INFO;
    command[1] = info;
 
    int retval = cmsis_dap_xfer(cmsis_dap_handle, 2);
    if (retval != ERROR_OK) {
        LOG_ERROR("CMSIS-DAP command CMD_INFO failed.");
        return ERROR_JTAG_DEVICE_ERROR;
    }
 
    *data = &cmsis_dap_handle->response[1];
 
    return ERROR_OK;
}
 
static int cmsis_dap_cmd_dap_led(uint8_t led, uint8_t state)
{
    uint8_t *command = cmsis_dap_handle->command;
 
    command[0] = CMD_DAP_LED;
    command[1] = led;
    command[2] = state;
 
    int retval = cmsis_dap_xfer(cmsis_dap_handle, 3);
    if (retval != ERROR_OK || cmsis_dap_handle->response[1] != DAP_OK) {
        LOG_ERROR("CMSIS-DAP command CMD_LED failed.");
        return ERROR_JTAG_DEVICE_ERROR;
    }
 
    return ERROR_OK;
}
 
static int cmsis_dap_cmd_dap_connect(uint8_t mode)
{
    uint8_t *command = cmsis_dap_handle->command;
 
    command[0] = CMD_DAP_CONNECT;
    command[1] = mode;
 
    int retval = cmsis_dap_xfer(cmsis_dap_handle, 2);
    if (retval != ERROR_OK) {
        LOG_ERROR("CMSIS-DAP command CMD_CONNECT failed.");
        return ERROR_JTAG_DEVICE_ERROR;
    }
 
    if (cmsis_dap_handle->response[1] != mode) {
        LOG_ERROR("CMSIS-DAP failed to connect in mode (%d)", mode);
        return ERROR_JTAG_DEVICE_ERROR;
    }
 
    return ERROR_OK;
}
 
static int cmsis_dap_cmd_dap_disconnect(void)
{
    uint8_t *command = cmsis_dap_handle->command;
 
    command[0] = CMD_DAP_DISCONNECT;
 
    int retval = cmsis_dap_xfer(cmsis_dap_handle, 1);
    if (retval != ERROR_OK || cmsis_dap_handle->response[1] != DAP_OK) {
        LOG_ERROR("CMSIS-DAP command CMD_DISCONNECT failed.");
        return ERROR_JTAG_DEVICE_ERROR;
    }
 
    return ERROR_OK;
}
 
static int cmsis_dap_cmd_dap_tfer_configure(uint8_t idle, uint16_t retry_count, uint16_t match_retry)
{
    uint8_t *command = cmsis_dap_handle->command;
 
    command[0] = CMD_DAP_TFER_CONFIGURE;
    command[1] = idle;
    h_u16_to_le(&command[2], retry_count);
    h_u16_to_le(&command[4], match_retry);
 
    int retval = cmsis_dap_xfer(cmsis_dap_handle, 6);
    if (retval != ERROR_OK || cmsis_dap_handle->response[1] != DAP_OK) {
        LOG_ERROR("CMSIS-DAP command CMD_TFER_Configure failed.");
        return ERROR_JTAG_DEVICE_ERROR;
    }
 
    return ERROR_OK;
}
 
static int cmsis_dap_cmd_dap_swd_configure(uint8_t cfg)
{
    uint8_t *command = cmsis_dap_handle->command;
 
    command[0] = CMD_DAP_SWD_CONFIGURE;
    command[1] = cfg;
 
    int retval = cmsis_dap_xfer(cmsis_dap_handle, 2);
    if (retval != ERROR_OK || cmsis_dap_handle->response[1] != DAP_OK) {
        LOG_ERROR("CMSIS-DAP command CMD_SWD_Configure failed.");
        return ERROR_JTAG_DEVICE_ERROR;
    }
 
    return ERROR_OK;
}
 
#if 0
static int cmsis_dap_cmd_dap_delay(uint16_t delay_us)
{
    uint8_t *command = cmsis_dap_handle->command;
 
    command[0] = CMD_DAP_DELAY;
    h_u16_to_le(&command[1], delay_us);
 
    int retval = cmsis_dap_xfer(cmsis_dap_handle, 3);
    if (retval != ERROR_OK || cmsis_dap_handle->response[1] != DAP_OK) {
        LOG_ERROR("CMSIS-DAP command CMD_Delay failed.");
        return ERROR_JTAG_DEVICE_ERROR;
    }
 
    return ERROR_OK;
}
#endif
 
static int cmsis_dap_metacmd_targetsel(uint32_t instance_id)
{
    uint8_t *command = cmsis_dap_handle->command;
    const uint32_t seq_rd = 0x80, seq_wr = 0x00;
 
    /* SWD multi-drop requires a transfer ala CMD_DAP_TFER,
    but with no expectation of an SWD ACK response.  In
    CMSIS-DAP v1.20 and v2.00, CMD_DAP_SWD_SEQUENCE was
    added to allow this special sequence to be generated.
    The purpose of this operation is to select the target
    corresponding to the instance_id that is written */
 
    LOG_DEBUG_IO("DP write reg TARGETSEL %" PRIx32, instance_id);
 
    size_t idx = 0;
    command[idx++] = CMD_DAP_SWD_SEQUENCE;
    command[idx++] = 3; /* sequence count */
 
    /* sequence 0: packet request for TARGETSEL */
    command[idx++] = seq_wr | 8;
    command[idx++] = SWD_CMD_START | swd_cmd(false, false, DP_TARGETSEL) | SWD_CMD_STOP | SWD_CMD_PARK;
 
    /* sequence 1: read Trn ACK Trn, no expectation for target to ACK  */
    command[idx++] = seq_rd | 5;
 
    /* sequence 2: WDATA plus parity */
    command[idx++] = seq_wr | (32 + 1);
    h_u32_to_le(command + idx, instance_id);
    idx += 4;
    command[idx++] = parity_u32(instance_id);
 
    int retval = cmsis_dap_xfer(cmsis_dap_handle, idx);
    if (retval != ERROR_OK || cmsis_dap_handle->response[1] != DAP_OK) {
        LOG_ERROR("CMSIS-DAP command SWD_Sequence failed.");
        return ERROR_JTAG_DEVICE_ERROR;
    }
 
    return ERROR_OK;
}
 
static int cmsis_dap_cmd_dap_swo_transport(uint8_t transport)
{
    uint8_t *command = cmsis_dap_handle->command;
 
    command[0] = CMD_DAP_SWO_TRANSPORT;
    command[1] = transport;
 
    int retval = cmsis_dap_xfer(cmsis_dap_handle, 2);
    if (retval != ERROR_OK || cmsis_dap_handle->response[1] != DAP_OK) {
        LOG_ERROR("CMSIS-DAP: command CMD_SWO_Transport(%d) failed.", transport);
        return ERROR_JTAG_DEVICE_ERROR;
    }
 
    return ERROR_OK;
}
 
static int cmsis_dap_cmd_dap_swo_mode(uint8_t mode)
{
    uint8_t *command = cmsis_dap_handle->command;
 
    command[0] = CMD_DAP_SWO_MODE;
    command[1] = mode;
 
    int retval = cmsis_dap_xfer(cmsis_dap_handle, 2);
    if (retval != ERROR_OK || cmsis_dap_handle->response[1] != DAP_OK) {
        LOG_ERROR("CMSIS-DAP: command CMD_SWO_Mode(%d) failed.", mode);
        return ERROR_JTAG_DEVICE_ERROR;
    }
 
    return ERROR_OK;
}
 
static int cmsis_dap_cmd_dap_swo_baudrate(
                    uint32_t in_baudrate,
                    uint32_t *dev_baudrate)
{
    uint8_t *command = cmsis_dap_handle->command;
 
    command[0] = CMD_DAP_SWO_BAUDRATE;
    h_u32_to_le(&command[1], in_baudrate);
 
    int retval = cmsis_dap_xfer(cmsis_dap_handle, 5);
    uint32_t rvbr = le_to_h_u32(&cmsis_dap_handle->response[1]);
    if (retval != ERROR_OK || rvbr == 0) {
        LOG_ERROR("CMSIS-DAP: command CMD_SWO_Baudrate(%u) -> %u failed.", in_baudrate, rvbr);
        if (dev_baudrate)
            *dev_baudrate = 0;
        return ERROR_JTAG_DEVICE_ERROR;
    }
 
    if (dev_baudrate)
        *dev_baudrate = rvbr;
 
    return ERROR_OK;
}
 
static int cmsis_dap_cmd_dap_swo_control(uint8_t control)
{
    uint8_t *command = cmsis_dap_handle->command;
 
    command[0] = CMD_DAP_SWO_CONTROL;
    command[1] = control;
 
    int retval = cmsis_dap_xfer(cmsis_dap_handle, 2);
    if (retval != ERROR_OK || cmsis_dap_handle->response[1] != DAP_OK) {
        LOG_ERROR("CMSIS-DAP: command CMD_SWO_Control(%d) failed.", control);
        return ERROR_JTAG_DEVICE_ERROR;
    }
 
    return ERROR_OK;
}
 
static int cmsis_dap_cmd_dap_swo_status(
                    uint8_t *trace_status,
                    size_t *trace_count)
{
    uint8_t *command = cmsis_dap_handle->command;
 
    command[0] = CMD_DAP_SWO_STATUS;
 
    int retval = cmsis_dap_xfer(cmsis_dap_handle, 1);
    if (retval != ERROR_OK) {
        LOG_ERROR("CMSIS-DAP: command CMD_SWO_Status failed.");
        return ERROR_JTAG_DEVICE_ERROR;
    }
 
    if (trace_status)
        *trace_status = cmsis_dap_handle->response[1];
    if (trace_count)
        *trace_count = le_to_h_u32(&cmsis_dap_handle->response[2]);
 
    return ERROR_OK;
}
 
static int cmsis_dap_cmd_dap_swo_data(
                    size_t max_trace_count,
                    uint8_t *trace_status,
                    size_t *trace_count,
                    uint8_t *data)
{
    uint8_t *command = cmsis_dap_handle->command;
 
    command[0] = CMD_DAP_SWO_DATA;
    h_u16_to_le(&command[1], max_trace_count);
 
    int retval = cmsis_dap_xfer(cmsis_dap_handle, 3);
    if (retval != ERROR_OK) {
        LOG_ERROR("CMSIS-DAP: command CMD_SWO_Data failed.");
        return ERROR_JTAG_DEVICE_ERROR;
    }
 
    *trace_status = cmsis_dap_handle->response[1];
    *trace_count = le_to_h_u16(&cmsis_dap_handle->response[2]);
 
    if (*trace_count > 0)
        memcpy(data, &cmsis_dap_handle->response[4], *trace_count);
 
    return ERROR_OK;
}
 
static void cmsis_dap_swd_discard_all_pending(struct cmsis_dap *dap)
{
    for (unsigned int i = 0; i < MAX_PENDING_REQUESTS; i++)
        dap->pending_fifo[i].transfer_count = 0;
 
    dap->pending_fifo_put_idx = 0;
    dap->pending_fifo_get_idx = 0;
    dap->pending_fifo_block_count = 0;
}
 
static void cmsis_dap_swd_cancel_transfers(struct cmsis_dap *dap)
{
    dap->backend->cancel_all(dap);
    cmsis_dap_flush_read(dap);
    cmsis_dap_swd_discard_all_pending(dap);
}
 
static void cmsis_dap_swd_write_from_queue(struct cmsis_dap *dap)
{
    uint8_t *command = dap->command;
    struct pending_request_block *block = &dap->pending_fifo[dap->pending_fifo_put_idx];
 
    assert(dap->write_count + dap->read_count == block->transfer_count);
 
    /* Reset packet size check counters for the next packet */
    dap->write_count = 0;
    dap->read_count = 0;
 
    LOG_DEBUG_IO("Executing %d queued transactions from FIFO index %u%s",
                 block->transfer_count, dap->pending_fifo_put_idx,
                 cmsis_dap_handle->swd_cmds_differ ? "" : ", same swd ops");
 
    if (queued_retval != ERROR_OK) {
        LOG_DEBUG("Skipping due to previous errors: %d", queued_retval);
        goto skip;
    }
 
    if (block->transfer_count == 0) {
        LOG_ERROR("internal: write an empty queue?!");
        goto skip;
    }
 
    bool block_cmd = !cmsis_dap_handle->swd_cmds_differ
                     && block->transfer_count >= CMD_DAP_TFER_BLOCK_MIN_OPS;
    block->command = block_cmd ? CMD_DAP_TFER_BLOCK : CMD_DAP_TFER;
 
    command[0] = block->command;
    command[1] = 0x00;  /* DAP Index */
 
    unsigned int idx;
    if (block_cmd) {
        h_u16_to_le(&command[2], block->transfer_count);
        idx = 4;    /* The first transfer will store the common DAP register */
    } else {
        command[2] = block->transfer_count;
        idx = 3;
    }
 
    for (unsigned int i = 0; i < block->transfer_count; i++) {
        struct pending_transfer_result *transfer = &(block->transfers[i]);
        uint8_t cmd = transfer->cmd;
        uint32_t data = transfer->data;
 
        LOG_DEBUG_IO("%s %s reg %x %" PRIx32,
                cmd & SWD_CMD_APNDP ? "AP" : "DP",
                cmd & SWD_CMD_RNW ? "read" : "write",
              (cmd & SWD_CMD_A32) >> 1, data);
 
        /* When proper WAIT handling is implemented in the
         * common SWD framework, this kludge can be
         * removed. However, this might lead to minor
         * performance degradation as the adapter wouldn't be
         * able to automatically retry anything (because ARM
         * has forgotten to implement sticky error flags
         * clearing). See also comments regarding
         * cmsis_dap_cmd_dap_tfer_configure() and
         * cmsis_dap_cmd_dap_swd_configure() in
         * cmsis_dap_init().
         */
        if (!(cmd & SWD_CMD_RNW) &&
            !(cmd & SWD_CMD_APNDP) &&
            (cmd & SWD_CMD_A32) >> 1 == DP_CTRL_STAT &&
            (data & CORUNDETECT)) {
            LOG_DEBUG("refusing to enable sticky overrun detection");
            data &= ~CORUNDETECT;
        }
 
        if (!block_cmd || i == 0)
            command[idx++] = (cmd >> 1) & 0x0f;
 
        if (!(cmd & SWD_CMD_RNW)) {
            h_u32_to_le(&command[idx], data);
            idx += 4;
        }
    }
 
    int retval = dap->backend->write(dap, idx, LIBUSB_TIMEOUT_MS);
    if (retval < 0) {
        queued_retval = retval;
        goto skip;
    }
 
    unsigned int packet_count = cmsis_dap_quirk_mode ? 1 : dap->packet_count;
    dap->pending_fifo_put_idx = (dap->pending_fifo_put_idx + 1) % packet_count;
    dap->pending_fifo_block_count++;
    if (dap->pending_fifo_block_count > packet_count)
        LOG_ERROR("internal: too much pending writes %u", dap->pending_fifo_block_count);
 
    return;
 
skip:
    block->transfer_count = 0;
}
 
static void cmsis_dap_swd_read_process(struct cmsis_dap *dap, enum cmsis_dap_blocking blocking)
{
    int retval;
    struct pending_request_block *block = &dap->pending_fifo[dap->pending_fifo_get_idx];
 
    if (dap->pending_fifo_block_count == 0) {
        LOG_ERROR("internal: no pending write when reading?!");
        return;
    }
 
    if (queued_retval != ERROR_OK) {
        /* keep reading blocks until the pipeline is empty */
        retval = dap->backend->read(dap, 10, CMSIS_DAP_BLOCKING);
        if (retval == ERROR_TIMEOUT_REACHED || retval == 0) {
            /* timeout means that we flushed the pipeline,
             * we can safely discard remaining pending requests */
            cmsis_dap_swd_discard_all_pending(dap);
            return;
        }
        goto skip;
    }
 
    /* get reply */
    retval = dap->backend->read(dap, LIBUSB_TIMEOUT_MS, blocking);
    bool timeout = (retval == ERROR_TIMEOUT_REACHED || retval == 0);
    if (timeout && blocking == CMSIS_DAP_NON_BLOCKING)
        return;
 
    if (retval <= 0) {
        LOG_DEBUG("error reading adapter response");
        queued_retval = ERROR_FAIL;
        if (timeout) {
            /* timeout means that we flushed the pipeline,
             * we can safely discard remaining pending requests */
            cmsis_dap_swd_discard_all_pending(dap);
            return;
        }
        goto skip;
    }
 
    uint8_t *resp = dap->response;
    if (resp[0] != block->command) {
        LOG_ERROR("CMSIS-DAP command mismatch. Expected 0x%x received 0x%" PRIx8,
            block->command, resp[0]);
        cmsis_dap_swd_cancel_transfers(dap);
        queued_retval = ERROR_FAIL;
        return;
    }
 
    unsigned int transfer_count;
    unsigned int idx;
    if (block->command == CMD_DAP_TFER_BLOCK) {
        transfer_count = le_to_h_u16(&resp[1]);
        idx = 3;
    } else {
        transfer_count = resp[1];
        idx = 2;
    }
    if (resp[idx] & 0x08) {
        LOG_DEBUG("CMSIS-DAP Protocol Error @ %d (wrong parity)", transfer_count);
        queued_retval = ERROR_FAIL;
        goto skip;
    }
    uint8_t ack = resp[idx++] & 0x07;
    if (ack != SWD_ACK_OK) {
        LOG_DEBUG("SWD ack not OK @ %d %s", transfer_count,
              ack == SWD_ACK_WAIT ? "WAIT" : ack == SWD_ACK_FAULT ? "FAULT" : "JUNK");
        queued_retval = swd_ack_to_error_code(ack);
        /* TODO: use results of transfers completed before the error occurred? */
        goto skip;
    }
 
    if (block->transfer_count != transfer_count) {
        LOG_ERROR("CMSIS-DAP transfer count mismatch: expected %d, got %d",
              block->transfer_count, transfer_count);
        cmsis_dap_swd_cancel_transfers(dap);
        queued_retval = ERROR_FAIL;
        return;
    }
 
    LOG_DEBUG_IO("Received results of %d queued transactions FIFO index %u, %s mode",
                 transfer_count, dap->pending_fifo_get_idx,
                 blocking ? "blocking" : "nonblocking");
 
    for (unsigned int i = 0; i < transfer_count; i++) {
        struct pending_transfer_result *transfer = &(block->transfers[i]);
        if (transfer->cmd & SWD_CMD_RNW) {
            static uint32_t last_read;
            uint32_t data = le_to_h_u32(&resp[idx]);
            uint32_t tmp = data;
            idx += 4;
 
            LOG_DEBUG_IO("Read result: %" PRIx32, data);
 
            /* Imitate posted AP reads */
            if ((transfer->cmd & SWD_CMD_APNDP) ||
                ((transfer->cmd & SWD_CMD_A32) >> 1 == DP_RDBUFF)) {
                tmp = last_read;
                last_read = data;
            }
 
            if (transfer->buffer)
                *(uint32_t *)(transfer->buffer) = tmp;
        }
    }
 
skip:
    block->transfer_count = 0;
    if (!cmsis_dap_quirk_mode && dap->packet_count > 1)
        dap->pending_fifo_get_idx = (dap->pending_fifo_get_idx + 1) % dap->packet_count;
    dap->pending_fifo_block_count--;
}
 
static int cmsis_dap_swd_run_queue(void)
{
    if (cmsis_dap_handle->write_count + cmsis_dap_handle->read_count) {
        if (cmsis_dap_handle->pending_fifo_block_count)
            cmsis_dap_swd_read_process(cmsis_dap_handle, CMSIS_DAP_NON_BLOCKING);
 
        cmsis_dap_swd_write_from_queue(cmsis_dap_handle);
    }
 
    while (cmsis_dap_handle->pending_fifo_block_count)
        cmsis_dap_swd_read_process(cmsis_dap_handle, CMSIS_DAP_BLOCKING);
 
    cmsis_dap_handle->pending_fifo_put_idx = 0;
    cmsis_dap_handle->pending_fifo_get_idx = 0;
 
    int retval = queued_retval;
    queued_retval = ERROR_OK;
 
    return retval;
}
 
static unsigned int cmsis_dap_tfer_cmd_size(unsigned int write_count,
                            unsigned int read_count, bool block_tfer)
{
    unsigned int size;
    if (block_tfer) {
        size = 5;                       /* DAP_TransferBlock header */
        size += write_count * 4;        /* data */
    } else {
        size = 3;                       /* DAP_Transfer header */
        size += write_count * (1 + 4);  /* DAP register + data */
        size += read_count;             /* DAP register */
    }
    return size;
}
 
static unsigned int cmsis_dap_tfer_resp_size(unsigned int write_count,
                            unsigned int read_count, bool block_tfer)
{
    unsigned int size;
    if (block_tfer)
        size = 4;                       /* DAP_TransferBlock response header */
    else
        size = 3;                       /* DAP_Transfer response header */
 
    size += read_count * 4;             /* data */
    return size;
}
 
static void cmsis_dap_swd_queue_cmd(uint8_t cmd, uint32_t *dst, uint32_t data)
{
    /* TARGETSEL register write cannot be queued */
    if (swd_cmd(false, false, DP_TARGETSEL) == cmd) {
        queued_retval = cmsis_dap_swd_run_queue();
 
        cmsis_dap_metacmd_targetsel(data);
        return;
    }
 
    /* Compute sizes of the DAP Transfer command and the expected response
     * for all queued and this operation */
    unsigned int write_count = cmsis_dap_handle->write_count;
    unsigned int read_count = cmsis_dap_handle->read_count;
    bool block_cmd;
    if (write_count + read_count < CMD_DAP_TFER_BLOCK_MIN_OPS)
        block_cmd = false;
    else
        block_cmd = !cmsis_dap_handle->swd_cmds_differ
                    && cmd == cmsis_dap_handle->common_swd_cmd;
 
    if (cmd & SWD_CMD_RNW)
        read_count++;
    else
        write_count++;
 
    unsigned int cmd_size = cmsis_dap_tfer_cmd_size(write_count, read_count,
                                                    block_cmd);
    unsigned int resp_size = cmsis_dap_tfer_resp_size(write_count, read_count,
                                                    block_cmd);
    unsigned int max_transfer_count = block_cmd ? 65535 : 255;
 
    /* Does the DAP Transfer command and also its expected response fit into one packet? */
    if (cmd_size > tfer_max_command_size
            || resp_size > tfer_max_response_size
            || write_count + read_count > max_transfer_count) {
        if (cmsis_dap_handle->pending_fifo_block_count)
            cmsis_dap_swd_read_process(cmsis_dap_handle, CMSIS_DAP_NON_BLOCKING);
 
        /* Not enough room in the queue. Run the queue. */
        cmsis_dap_swd_write_from_queue(cmsis_dap_handle);
 
        unsigned int packet_count = cmsis_dap_quirk_mode ? 1 : cmsis_dap_handle->packet_count;
        if (cmsis_dap_handle->pending_fifo_block_count >= packet_count)
            cmsis_dap_swd_read_process(cmsis_dap_handle, CMSIS_DAP_BLOCKING);
    }
 
    assert(cmsis_dap_handle->pending_fifo[cmsis_dap_handle->pending_fifo_put_idx].transfer_count < pending_queue_len);
 
    if (queued_retval != ERROR_OK)
        return;
 
    struct pending_request_block *block = &cmsis_dap_handle->pending_fifo[cmsis_dap_handle->pending_fifo_put_idx];
    struct pending_transfer_result *transfer = &(block->transfers[block->transfer_count]);
    transfer->data = data;
    transfer->cmd = cmd;
    if (block->transfer_count == 0) {
        cmsis_dap_handle->swd_cmds_differ = false;
        cmsis_dap_handle->common_swd_cmd = cmd;
    } else if (cmd != cmsis_dap_handle->common_swd_cmd) {
        cmsis_dap_handle->swd_cmds_differ = true;
    }
 
    if (cmd & SWD_CMD_RNW) {
        /* Queue a read transaction */
        transfer->buffer = dst;
        cmsis_dap_handle->read_count++;
    } else {
        cmsis_dap_handle->write_count++;
    }
    block->transfer_count++;
}
 
static void cmsis_dap_swd_write_reg(uint8_t cmd, uint32_t value, uint32_t ap_delay_clk)
{
    assert(!(cmd & SWD_CMD_RNW));
    cmsis_dap_swd_queue_cmd(cmd, NULL, value);
}
 
static void cmsis_dap_swd_read_reg(uint8_t cmd, uint32_t *value, uint32_t ap_delay_clk)
{
    assert(cmd & SWD_CMD_RNW);
    cmsis_dap_swd_queue_cmd(cmd, value, 0);
}
 
static int cmsis_dap_get_serial_info(void)
{
    uint8_t *data;
 
    int retval = cmsis_dap_cmd_dap_info(INFO_ID_SERNUM, &data);
    if (retval != ERROR_OK)
        return retval;
 
    if (data[0]) /* strlen */
        LOG_INFO("CMSIS-DAP: Serial# = %s", &data[1]);
 
    return ERROR_OK;
}
 
static int cmsis_dap_get_version_info(void)
{
    uint8_t *data;
 
    /* INFO_ID_FW_VER - string */
    int retval = cmsis_dap_cmd_dap_info(INFO_ID_FW_VER, &data);
    if (retval != ERROR_OK)
        return retval;
 
    if (data[0]) /* strlen */
        LOG_INFO("CMSIS-DAP: FW Version = %s", &data[1]);
 
    return ERROR_OK;
}
 
static int cmsis_dap_get_caps_info(void)
{
    uint8_t *data;
 
    /* INFO_ID_CAPS - byte */
    int retval = cmsis_dap_cmd_dap_info(INFO_ID_CAPS, &data);
    if (retval != ERROR_OK)
        return retval;
 
    if (data[0] == 1 || data[0] == 2) {
        uint16_t caps = data[1];
        if (data[0] == 2)
            caps |= (uint16_t)data[2] << 8;
 
        cmsis_dap_handle->caps = caps;
 
        for (unsigned int i = 0; i < INFO_CAPS__NUM_CAPS; ++i) {
            if (caps & BIT(i))
                LOG_INFO("CMSIS-DAP: %s", info_caps_str[i]);
        }
    }
 
    return ERROR_OK;
}
 
static int cmsis_dap_get_swo_buf_sz(uint32_t *swo_buf_sz)
{
    uint8_t *data;
 
    /* INFO_ID_SWO_BUF_SZ - word */
    int retval = cmsis_dap_cmd_dap_info(INFO_ID_SWO_BUF_SZ, &data);
    if (retval != ERROR_OK)
        return retval;
 
    if (data[0] != 4)
        return ERROR_FAIL;
 
    *swo_buf_sz = le_to_h_u32(&data[1]);
 
    LOG_INFO("CMSIS-DAP: SWO Trace Buffer Size = %u bytes", *swo_buf_sz);
 
    return ERROR_OK;
}
 
static int cmsis_dap_get_status(void)
{
    uint8_t d;
 
    int retval = cmsis_dap_cmd_dap_swj_pins(0, 0, 0, &d);
 
    if (retval == ERROR_OK) {
        LOG_INFO("SWCLK/TCK = %d SWDIO/TMS = %d TDI = %d TDO = %d nTRST = %d nRESET = %d",
            (d & SWJ_PIN_TCK) ? 1 : 0,
            (d & SWJ_PIN_TMS) ? 1 : 0,
            (d & SWJ_PIN_TDI) ? 1 : 0,
            (d & SWJ_PIN_TDO) ? 1 : 0,
            (d & SWJ_PIN_TRST) ? 1 : 0,
            (d & SWJ_PIN_SRST) ? 1 : 0);
    }
 
    return retval;
}
 
static int cmsis_dap_swd_switch_seq(enum swd_special_seq seq)
{
    const uint8_t *s;
    unsigned int s_len;
    int retval;
 
    if (swd_mode)
        queued_retval = cmsis_dap_swd_run_queue();
 
    if (cmsis_dap_quirk_mode && seq != LINE_RESET &&
            (output_pins & (SWJ_PIN_SRST | SWJ_PIN_TRST))
                == (SWJ_PIN_SRST | SWJ_PIN_TRST)) {
        /* Following workaround deasserts reset on most adapters.
         * Do not reconnect if a reset line is active!
         * Reconnecting would break connecting under reset. */
 
        /* First disconnect before connecting, Atmel EDBG needs it for SAMD/R/L/C */
        cmsis_dap_cmd_dap_disconnect();
 
        /* When we are reconnecting, DAP_Connect needs to be rerun, at
         * least on Keil ULINK-ME */
        retval = cmsis_dap_cmd_dap_connect(CONNECT_SWD);
        if (retval != ERROR_OK)
            return retval;
    }
 
    switch (seq) {
    case LINE_RESET:
        LOG_DEBUG_IO("SWD line reset");
        s = swd_seq_line_reset;
        s_len = swd_seq_line_reset_len;
        break;
    case JTAG_TO_SWD:
        LOG_DEBUG("JTAG-to-SWD");
        s = swd_seq_jtag_to_swd;
        s_len = swd_seq_jtag_to_swd_len;
        break;
    case JTAG_TO_DORMANT:
        LOG_DEBUG("JTAG-to-DORMANT");
        s = swd_seq_jtag_to_dormant;
        s_len = swd_seq_jtag_to_dormant_len;
        break;
    case SWD_TO_JTAG:
        LOG_DEBUG("SWD-to-JTAG");
        s = swd_seq_swd_to_jtag;
        s_len = swd_seq_swd_to_jtag_len;
        break;
    case SWD_TO_DORMANT:
        LOG_DEBUG("SWD-to-DORMANT");
        s = swd_seq_swd_to_dormant;
        s_len = swd_seq_swd_to_dormant_len;
        break;
    case DORMANT_TO_SWD:
        LOG_DEBUG("DORMANT-to-SWD");
        s = swd_seq_dormant_to_swd;
        s_len = swd_seq_dormant_to_swd_len;
        break;
    case DORMANT_TO_JTAG:
        LOG_DEBUG("DORMANT-to-JTAG");
        s = swd_seq_dormant_to_jtag;
        s_len = swd_seq_dormant_to_jtag_len;
        break;
    default:
        LOG_ERROR("Sequence %d not supported", seq);
        return ERROR_FAIL;
    }
 
    retval = cmsis_dap_cmd_dap_swj_sequence(s_len, s);
    if (retval != ERROR_OK)
        return retval;
 
    /* Atmel EDBG needs renew clock setting after SWJ_Sequence
     * otherwise default frequency is used */
    return cmsis_dap_cmd_dap_swj_clock(adapter_get_speed_khz());
}
 
static int cmsis_dap_swd_open(void)
{
    if (!(cmsis_dap_handle->caps & INFO_CAPS_SWD)) {
        LOG_ERROR("CMSIS-DAP: SWD not supported");
        return ERROR_JTAG_DEVICE_ERROR;
    }
 
    int retval = cmsis_dap_cmd_dap_connect(CONNECT_SWD);
    if (retval != ERROR_OK)
        return retval;
 
    /* Add more setup here.??... */
 
    LOG_INFO("CMSIS-DAP: Interface Initialised (SWD)");
    return ERROR_OK;
}
 
static int cmsis_dap_init(void)
{
    uint8_t *data;
 
    int retval = cmsis_dap_open();
    if (retval != ERROR_OK)
        return retval;
 
    cmsis_dap_flush_read(cmsis_dap_handle);
 
    retval = cmsis_dap_get_caps_info();
    if (retval != ERROR_OK)
        return retval;
 
    retval = cmsis_dap_get_version_info();
    if (retval != ERROR_OK)
        return retval;
 
    retval = cmsis_dap_get_serial_info();
    if (retval != ERROR_OK)
        return retval;
 
    if (swd_mode) {
        retval = cmsis_dap_swd_open();
        if (retval != ERROR_OK)
            return retval;
    } else {
        /* Connect in JTAG mode */
        if (!(cmsis_dap_handle->caps & INFO_CAPS_JTAG)) {
            LOG_ERROR("CMSIS-DAP: JTAG not supported");
            return ERROR_JTAG_DEVICE_ERROR;
        }
 
        retval = cmsis_dap_cmd_dap_connect(CONNECT_JTAG);
        if (retval != ERROR_OK)
            return retval;
 
        LOG_INFO("CMSIS-DAP: Interface Initialised (JTAG)");
    }
 
    /* Be conservative and suppress submitting multiple HID requests
     * until we get packet count info from the adaptor */
    cmsis_dap_handle->packet_count = 1;
 
    /* INFO_ID_PKT_SZ - short */
    retval = cmsis_dap_cmd_dap_info(INFO_ID_PKT_SZ, &data);
    if (retval != ERROR_OK)
        goto init_err;
 
    if (data[0] == 2) {  /* short */
        uint16_t pkt_sz = data[1] + (data[2] << 8);
        if (pkt_sz != cmsis_dap_handle->packet_size) {
            cmsis_dap_handle->backend->packet_buffer_free(cmsis_dap_handle);
            retval = cmsis_dap_handle->backend->packet_buffer_alloc(cmsis_dap_handle, pkt_sz);
            if (retval != ERROR_OK)
                goto init_err;
 
            LOG_DEBUG("CMSIS-DAP: Packet Size = %" PRIu16, pkt_sz);
        }
    }
 
    /* Maximal number of transfers which fit to one packet:
     * Limited by response size: 3 bytes of response header + 4 per read
     * Plus writes to full command size: 3 bytes cmd header + 1 per read + 5 per write */
    tfer_max_command_size = cmsis_dap_handle->packet_usable_size;
    tfer_max_response_size = cmsis_dap_handle->packet_usable_size;
    unsigned int max_reads = tfer_max_response_size / 4;
    pending_queue_len = max_reads + (tfer_max_command_size - max_reads) / 5;
    cmsis_dap_handle->write_count = 0;
    cmsis_dap_handle->read_count = 0;
 
    /* INFO_ID_PKT_CNT - byte */
    retval = cmsis_dap_cmd_dap_info(INFO_ID_PKT_CNT, &data);
    if (retval != ERROR_OK)
        goto init_err;
 
    if (data[0] == 1) { /* byte */
        unsigned int pkt_cnt = data[1];
        if (pkt_cnt > 1)
            cmsis_dap_handle->packet_count = MIN(MAX_PENDING_REQUESTS, pkt_cnt);
 
        LOG_DEBUG("CMSIS-DAP: Packet Count = %u", pkt_cnt);
    }
 
    LOG_DEBUG("Allocating FIFO for %u pending packets", cmsis_dap_handle->packet_count);
    for (unsigned int i = 0; i < cmsis_dap_handle->packet_count; i++) {
        cmsis_dap_handle->pending_fifo[i].transfers = malloc(pending_queue_len
                                     * sizeof(struct pending_transfer_result));
        if (!cmsis_dap_handle->pending_fifo[i].transfers) {
            LOG_ERROR("Unable to allocate memory for CMSIS-DAP queue");
            retval = ERROR_FAIL;
            goto init_err;
        }
    }
 
    /* Intentionally not checked for error, just logs an info message
     * not vital for further debugging */
    (void)cmsis_dap_get_status();
 
    /* Now try to connect to the target
     * TODO: This is all SWD only @ present */
    retval = cmsis_dap_cmd_dap_swj_clock(adapter_get_speed_khz());
    if (retval != ERROR_OK)
        goto init_err;
 
    /* Ask CMSIS-DAP to automatically retry on receiving WAIT for
     * up to 64 times. This must be changed to 0 if sticky
     * overrun detection is enabled. */
    retval = cmsis_dap_cmd_dap_tfer_configure(0, 64, 0);
    if (retval != ERROR_OK)
        goto init_err;
 
    if (swd_mode) {
        /* Data Phase (bit 2) must be set to 1 if sticky overrun
         * detection is enabled */
        retval = cmsis_dap_cmd_dap_swd_configure(0);    /* 1 TRN, no Data Phase */
        if (retval != ERROR_OK)
            goto init_err;
    }
    /* Both LEDs on */
    /* Intentionally not checked for error, debugging will work
     * without LEDs */
    (void)cmsis_dap_cmd_dap_led(LED_ID_CONNECT, LED_ON);
    (void)cmsis_dap_cmd_dap_led(LED_ID_RUN, LED_ON);
 
    /* support connecting with srst asserted */
    enum reset_types jtag_reset_config = jtag_get_reset_config();
 
    if (jtag_reset_config & RESET_CNCT_UNDER_SRST) {
        if (jtag_reset_config & RESET_SRST_NO_GATING) {
            retval = cmsis_dap_cmd_dap_swj_pins(0, SWJ_PIN_SRST, 0, NULL);
            if (retval != ERROR_OK)
                goto init_err;
            LOG_INFO("Connecting under reset");
        }
    }
    LOG_INFO("CMSIS-DAP: Interface ready");
    return ERROR_OK;
 
init_err:
    cmsis_dap_quit();
    return retval;
}
 
static int cmsis_dap_swd_init(void)
{
    swd_mode = true;
    return ERROR_OK;
}
 
static int cmsis_dap_quit(void)
{
    cmsis_dap_cmd_dap_disconnect();
 
    /* Both LEDs off */
    cmsis_dap_cmd_dap_led(LED_ID_RUN, LED_OFF);
    cmsis_dap_cmd_dap_led(LED_ID_CONNECT, LED_OFF);
 
    cmsis_dap_close(cmsis_dap_handle);
 
    return ERROR_OK;
}
 
static int cmsis_dap_reset(int trst, int srst)
{
    /* Set both TRST and SRST even if they're not enabled as
     * there's no way to tristate them */
 
    output_pins = 0;
    if (!srst)
        output_pins |= SWJ_PIN_SRST;
    if (!trst)
        output_pins |= SWJ_PIN_TRST;
 
    int retval = cmsis_dap_cmd_dap_swj_pins(output_pins,
            SWJ_PIN_TRST | SWJ_PIN_SRST, 0, NULL);
    if (retval != ERROR_OK)
        LOG_ERROR("CMSIS-DAP: Interface reset failed");
    return retval;
}
 
static void cmsis_dap_execute_sleep(struct jtag_command *cmd)
{
#if 0
    int retval = cmsis_dap_cmd_dap_delay(cmd->cmd.sleep->us);
    if (retval != ERROR_OK)
#endif
        jtag_sleep(cmd->cmd.sleep->us);
}
 
/* Set TMS high for five TCK clocks, to move the TAP to the Test-Logic-Reset state */
static int cmsis_dap_execute_tlr_reset(struct jtag_command *cmd)
{
    LOG_INFO("cmsis-dap JTAG TLR_RESET");
    uint8_t seq = 0xff;
 
    int retval = cmsis_dap_cmd_dap_swj_sequence(8, &seq);
    if (retval == ERROR_OK)
        tap_set_state(TAP_RESET);
    return retval;
}
 
/* Set new end state */
static void cmsis_dap_end_state(enum tap_state state)
{
    if (tap_is_state_stable(state))
        tap_set_end_state(state);
    else {
        LOG_ERROR("BUG: %i is not a valid end state", state);
        exit(-1);
    }
}
 
#ifdef SPRINT_BINARY
static void sprint_binary(char *s, const uint8_t *buf, unsigned int offset, unsigned int len)
{
    if (!len)
        return;
 
    /*
    buf = { 0x18 } len=5 should result in: 11000
    buf = { 0xff 0x18 } len=13 should result in: 11111111 11000
    buf = { 0xc0 0x18 } offset=3 len=10 should result in: 11000 11000
        i=3 there means i/8 = 0 so c = 0xFF, and
    */
    for (unsigned int i = offset; i < offset + len; ++i) {
        uint8_t c = buf[i / 8], mask = 1 << (i % 8);
        if ((i != offset) && !(i % 8))
            putchar(' ');
        *s++ = (c & mask) ? '1' : '0';
    }
    *s = 0;
}
#endif
 
#ifdef CMSIS_DAP_JTAG_DEBUG
static void debug_parse_cmsis_buf(const uint8_t *cmd, int cmdlen)
{
    /* cmd is a usb packet to go to the cmsis-dap interface */
    printf("cmsis-dap buffer (%d b): ", cmdlen);
    for (int i = 0; i < cmdlen; ++i)
        printf(" %02x", cmd[i]);
    printf("\n");
    switch (cmd[0]) {
    case CMD_DAP_JTAG_SEQ: {
        printf("cmsis-dap jtag sequence command %02x (n=%d)\n", cmd[0], cmd[1]);
        /*
         * #1 = number of sequences
         * #2 = sequence info 1
         * #3...4+n_bytes-1 = sequence 1
         * #4+n_bytes = sequence info 2
         * #5+n_bytes = sequence 2 (single bit)
         */
        int pos = 2;
        for (int seq = 0; seq < cmd[1]; ++seq) {
            uint8_t info = cmd[pos++];
            int len = info & DAP_JTAG_SEQ_TCK;
            if (len == 0)
                len = 64;
            printf("  sequence %d starting %d: info %02x (len=%d tms=%d read_tdo=%d): ",
                seq, pos, info, len, info & DAP_JTAG_SEQ_TMS, info & DAP_JTAG_SEQ_TDO);
            for (int i = 0; i < DIV_ROUND_UP(len, 8); ++i)
                printf(" %02x", cmd[pos + i]);
            pos += DIV_ROUND_UP(len, 8);
            printf("\n");
        }
        if (pos != cmdlen) {
            printf("BUFFER LENGTH MISMATCH looks like %d but %d specified", pos, cmdlen);
            exit(-1);
        }
 
        break;
    }
    default:
        LOG_DEBUG("unknown cmsis-dap command %02x", cmd[1]);
        break;
    }
}
#endif
 
static void cmsis_dap_flush(void)
{
    if (!queued_seq_count)
        return;
 
    LOG_DEBUG_IO("Flushing %d queued sequences (%d bytes) with %d pending scan results to capture",
        queued_seq_count, queued_seq_buf_end, pending_scan_result_count);
 
    /* prepare CMSIS-DAP packet */
    uint8_t *command = cmsis_dap_handle->command;
    command[0] = CMD_DAP_JTAG_SEQ;
    command[1] = queued_seq_count;
    memcpy(&command[2], queued_seq_buf, queued_seq_buf_end);
 
#ifdef CMSIS_DAP_JTAG_DEBUG
    debug_parse_cmsis_buf(command, queued_seq_buf_end + 2);
#endif
 
    /* send command to USB device */
    int retval = cmsis_dap_xfer(cmsis_dap_handle, queued_seq_buf_end + 2);
 
    uint8_t *resp = cmsis_dap_handle->response;
    if (retval != ERROR_OK || resp[1] != DAP_OK) {
        LOG_ERROR("CMSIS-DAP command CMD_DAP_JTAG_SEQ failed.");
        exit(-1);
    }
 
#ifdef CMSIS_DAP_JTAG_DEBUG
    LOG_DEBUG_IO("USB response buf:");
    for (int c = 0; c < queued_seq_buf_end + 3; ++c)
        printf("%02X ", resp[c]);
    printf("\n");
#endif
 
    /* copy scan results into client buffers */
    for (int i = 0; i < pending_scan_result_count; ++i) {
        struct pending_scan_result *scan = &pending_scan_results[i];
        LOG_DEBUG_IO("Copying pending_scan_result %d/%d: %d bits from byte %d -> buffer + %d bits",
            i, pending_scan_result_count, scan->length, scan->first + 2, scan->buffer_offset);
#ifdef CMSIS_DAP_JTAG_DEBUG
        for (uint32_t b = 0; b < DIV_ROUND_UP(scan->length, 8); ++b)
            printf("%02X ", resp[2+scan->first+b]);
        printf("\n");
#endif
        bit_copy(scan->buffer, scan->buffer_offset, &resp[2 + scan->first], 0, scan->length);
    }
 
    /* reset */
    queued_seq_count = 0;
    queued_seq_buf_end = 0;
    queued_seq_tdo_ptr = 0;
    pending_scan_result_count = 0;
}
 
/* queue a sequence of bits to clock out TDI / in TDO, executing if the buffer is full.
 *
 * sequence=NULL means clock out zeros on TDI
 * tdo_buffer=NULL means don't capture TDO
 */
static void cmsis_dap_add_jtag_sequence(unsigned int s_len, const uint8_t *sequence,
                    unsigned int s_offset, bool tms,
                    uint8_t *tdo_buffer, unsigned int tdo_buffer_offset)
{
    LOG_DEBUG_IO("[at %d] %u bits, tms %s, seq offset %u, tdo buf %p, tdo offset %u",
        queued_seq_buf_end,
        s_len, tms ? "HIGH" : "LOW", s_offset, tdo_buffer, tdo_buffer_offset);
 
    if (s_len == 0)
        return;
 
    if (s_len > 64) {
        LOG_DEBUG_IO("START JTAG SEQ SPLIT");
        for (unsigned int offset = 0; offset < s_len; offset += 64) {
            unsigned int len = s_len - offset;
            if (len > 64)
                len = 64;
            LOG_DEBUG_IO("Splitting long jtag sequence: %u-bit chunk starting at offset %u", len, offset);
            cmsis_dap_add_jtag_sequence(
                len,
                sequence,
                s_offset + offset,
                tms,
                tdo_buffer,
                !tdo_buffer ? 0 : (tdo_buffer_offset + offset)
                );
        }
        LOG_DEBUG_IO("END JTAG SEQ SPLIT");
        return;
    }
 
    unsigned int cmd_len = 1 + DIV_ROUND_UP(s_len, 8);
    if (queued_seq_count >= 255 || queued_seq_buf_end + cmd_len > QUEUED_SEQ_BUF_LEN)
        /* empty out the buffer */
        cmsis_dap_flush();
 
    ++queued_seq_count;
 
    /* control byte */
    queued_seq_buf[queued_seq_buf_end] =
        (tms ? DAP_JTAG_SEQ_TMS : 0) |
        (tdo_buffer ? DAP_JTAG_SEQ_TDO : 0) |
        (s_len == 64 ? 0 : s_len);
 
    if (sequence)
        bit_copy(&queued_seq_buf[queued_seq_buf_end + 1], 0, sequence, s_offset, s_len);
    else
        memset(&queued_seq_buf[queued_seq_buf_end + 1], 0, DIV_ROUND_UP(s_len, 8));
 
    queued_seq_buf_end += cmd_len;
 
    if (tdo_buffer) {
        struct pending_scan_result *scan = &pending_scan_results[pending_scan_result_count++];
        scan->first = queued_seq_tdo_ptr;
        queued_seq_tdo_ptr += DIV_ROUND_UP(s_len, 8);
        scan->length = s_len;
        scan->buffer = tdo_buffer;
        scan->buffer_offset = tdo_buffer_offset;
    }
}
 
/* queue a sequence of bits to clock out TMS, executing if the buffer is full */
static void cmsis_dap_add_tms_sequence(const uint8_t *sequence, int s_len)
{
    LOG_DEBUG_IO("%d bits: %02X", s_len, *sequence);
    /* we use a series of CMD_DAP_JTAG_SEQ commands to toggle TMS,
       because even though it seems ridiculously inefficient, it
       allows us to combine TMS and scan sequences into the same
       USB packet. */
    /* TODO: combine runs of the same tms value */
    for (int i = 0; i < s_len; ++i) {
        bool bit = (sequence[i / 8] & (1 << (i % 8))) != 0;
        cmsis_dap_add_jtag_sequence(1, NULL, 0, bit, NULL, 0);
    }
}
 
/* Move to the end state by queuing a sequence to clock into TMS */
static void cmsis_dap_state_move(void)
{
    uint8_t tms_scan = tap_get_tms_path(tap_get_state(), tap_get_end_state());
    uint8_t tms_scan_bits = tap_get_tms_path_len(tap_get_state(), tap_get_end_state());
 
    LOG_DEBUG_IO("state move from %s to %s: %d clocks, %02X on tms",
        tap_state_name(tap_get_state()), tap_state_name(tap_get_end_state()),
        tms_scan_bits, tms_scan);
    cmsis_dap_add_tms_sequence(&tms_scan, tms_scan_bits);
 
    tap_set_state(tap_get_end_state());
}
 
 
/* Execute a JTAG scan operation by queueing TMS and TDI/TDO sequences */
static void cmsis_dap_execute_scan(struct jtag_command *cmd)
{
    LOG_DEBUG_IO("%s type:%d", cmd->cmd.scan->ir_scan ? "IRSCAN" : "DRSCAN",
        jtag_scan_type(cmd->cmd.scan));
 
    /* Make sure there are no trailing fields with num_bits == 0, or the logic below will fail. */
    while (cmd->cmd.scan->num_fields > 0
            && cmd->cmd.scan->fields[cmd->cmd.scan->num_fields - 1].num_bits == 0) {
        cmd->cmd.scan->num_fields--;
        LOG_DEBUG("discarding trailing empty field");
    }
 
    if (!cmd->cmd.scan->num_fields) {
        LOG_DEBUG("empty scan, doing nothing");
        return;
    }
 
    if (cmd->cmd.scan->ir_scan) {
        if (tap_get_state() != TAP_IRSHIFT) {
            cmsis_dap_end_state(TAP_IRSHIFT);
            cmsis_dap_state_move();
        }
    } else {
        if (tap_get_state() != TAP_DRSHIFT) {
            cmsis_dap_end_state(TAP_DRSHIFT);
            cmsis_dap_state_move();
        }
    }
 
    cmsis_dap_end_state(cmd->cmd.scan->end_state);
 
    struct scan_field *field = cmd->cmd.scan->fields;
    unsigned int scan_size = 0;
 
    for (unsigned int i = 0; i < cmd->cmd.scan->num_fields; i++, field++) {
        scan_size += field->num_bits;
        LOG_DEBUG_IO("%s%s field %u/%u %u bits",
            field->in_value ? "in" : "",
            field->out_value ? "out" : "",
            i,
            cmd->cmd.scan->num_fields,
            field->num_bits);
 
        if (i == cmd->cmd.scan->num_fields - 1 && tap_get_state() != tap_get_end_state()) {
            LOG_DEBUG_IO("Last field and have to move out of SHIFT state");
            /* Last field, and we're leaving IRSHIFT/DRSHIFT. Clock last bit during tap
             * movement. This last field can't have length zero, it was checked above. */
            cmsis_dap_add_jtag_sequence(
                field->num_bits - 1, /* number of bits to clock */
                field->out_value, /* output sequence */
                0, /* output offset */
                false, /* TMS low */
                field->in_value,
                0);
 
            /* Clock the last bit out, with TMS high */
            uint8_t last_bit = 0;
            if (field->out_value)
                bit_copy(&last_bit, 0, field->out_value, field->num_bits - 1, 1);
            cmsis_dap_add_jtag_sequence(
                1,
                &last_bit,
                0,
                true,
                field->in_value,
                field->num_bits - 1);
            tap_set_state(tap_state_transition(tap_get_state(), 1));
 
            /* Now clock one more cycle, with TMS low, to get us into a PAUSE state */
            cmsis_dap_add_jtag_sequence(
                1,
                &last_bit,
                0,
                false,
                NULL,
                0);
            tap_set_state(tap_state_transition(tap_get_state(), 0));
        } else {
            LOG_DEBUG_IO("Internal field, staying in SHIFT state afterwards");
            /* Clocking part of a sequence into DR or IR with TMS=0,
               leaving TMS=0 at the end so we can continue later */
            cmsis_dap_add_jtag_sequence(
                field->num_bits,
                field->out_value,
                0,
                false,
                field->in_value,
                0);
        }
    }
 
    if (tap_get_state() != tap_get_end_state()) {
        cmsis_dap_end_state(tap_get_end_state());
        cmsis_dap_state_move();
    }
 
    LOG_DEBUG_IO("%s scan, %i bits, end in %s",
        (cmd->cmd.scan->ir_scan) ? "IR" : "DR", scan_size,
        tap_state_name(tap_get_end_state()));
}
 
static void cmsis_dap_pathmove(int num_states, enum tap_state *path)
{
    uint8_t tms0 = 0x00;
    uint8_t tms1 = 0xff;
 
    for (int i = 0; i < num_states; i++) {
        if (path[i] == tap_state_transition(tap_get_state(), false))
            cmsis_dap_add_tms_sequence(&tms0, 1);
        else if (path[i] == tap_state_transition(tap_get_state(), true))
            cmsis_dap_add_tms_sequence(&tms1, 1);
        else {
            LOG_ERROR("BUG: %s -> %s isn't a valid TAP transition.",
                  tap_state_name(tap_get_state()), tap_state_name(path[i]));
            exit(-1);
        }
 
        tap_set_state(path[i]);
    }
 
    cmsis_dap_end_state(tap_get_state());
}
 
static void cmsis_dap_execute_pathmove(struct jtag_command *cmd)
{
    LOG_DEBUG_IO("pathmove: %i states, end in %i",
              cmd->cmd.pathmove->num_states,
           cmd->cmd.pathmove->path[cmd->cmd.pathmove->num_states - 1]);
 
    cmsis_dap_pathmove(cmd->cmd.pathmove->num_states, cmd->cmd.pathmove->path);
}
 
static void cmsis_dap_stableclocks(unsigned int num_cycles)
{
    uint8_t tms = tap_get_state() == TAP_RESET;
    /* TODO: Perform optimizations? */
    /* Execute num_cycles. */
    for (unsigned int i = 0; i < num_cycles; i++)
        cmsis_dap_add_tms_sequence(&tms, 1);
}
 
static void cmsis_dap_runtest(unsigned int num_cycles)
{
    enum tap_state saved_end_state = tap_get_end_state();
 
    /* Only do a state_move when we're not already in IDLE. */
    if (tap_get_state() != TAP_IDLE) {
        cmsis_dap_end_state(TAP_IDLE);
        cmsis_dap_state_move();
    }
    cmsis_dap_stableclocks(num_cycles);
 
    /* Finish in end_state. */
    cmsis_dap_end_state(saved_end_state);
 
    if (tap_get_state() != tap_get_end_state())
        cmsis_dap_state_move();
}
 
static void cmsis_dap_execute_runtest(struct jtag_command *cmd)
{
    LOG_DEBUG_IO("runtest %u cycles, end in %i", cmd->cmd.runtest->num_cycles,
              cmd->cmd.runtest->end_state);
 
    cmsis_dap_end_state(cmd->cmd.runtest->end_state);
    cmsis_dap_runtest(cmd->cmd.runtest->num_cycles);
}
 
static void cmsis_dap_execute_stableclocks(struct jtag_command *cmd)
{
    LOG_DEBUG_IO("stableclocks %u cycles", cmd->cmd.runtest->num_cycles);
    cmsis_dap_stableclocks(cmd->cmd.runtest->num_cycles);
}
 
static void cmsis_dap_execute_tms(struct jtag_command *cmd)
{
    LOG_DEBUG_IO("TMS: %u bits", cmd->cmd.tms->num_bits);
    cmsis_dap_cmd_dap_swj_sequence(cmd->cmd.tms->num_bits, cmd->cmd.tms->bits);
}
 
/* TODO: Is there need to call cmsis_dap_flush() for the JTAG_PATHMOVE,
 * JTAG_RUNTEST, JTAG_STABLECLOCKS? */
static void cmsis_dap_execute_command(struct jtag_command *cmd)
{
    switch (cmd->type) {
    case JTAG_SLEEP:
        cmsis_dap_flush();
        cmsis_dap_execute_sleep(cmd);
        break;
    case JTAG_TLR_RESET:
        cmsis_dap_flush();
        cmsis_dap_execute_tlr_reset(cmd);
        break;
    case JTAG_SCAN:
        cmsis_dap_execute_scan(cmd);
        break;
    case JTAG_PATHMOVE:
        cmsis_dap_execute_pathmove(cmd);
        break;
    case JTAG_RUNTEST:
        cmsis_dap_execute_runtest(cmd);
        break;
    case JTAG_STABLECLOCKS:
        cmsis_dap_execute_stableclocks(cmd);
        break;
    case JTAG_TMS:
        cmsis_dap_execute_tms(cmd);
        break;
    default:
        LOG_ERROR("BUG: unknown JTAG command type 0x%X encountered", cmd->type);
        exit(-1);
    }
}
 
static int cmsis_dap_execute_queue(struct jtag_command *cmd_queue)
{
    struct jtag_command *cmd = cmd_queue;
 
    while (cmd) {
        cmsis_dap_execute_command(cmd);
        cmd = cmd->next;
    }
 
    cmsis_dap_flush();
 
    return ERROR_OK;
}
 
static int cmsis_dap_speed(int speed)
{
    if (speed == 0) {
        LOG_ERROR("RTCK not supported. Set nonzero \"adapter speed\".");
        return ERROR_JTAG_NOT_IMPLEMENTED;
    }
 
    return cmsis_dap_cmd_dap_swj_clock(speed);
}
 
static int cmsis_dap_speed_div(int speed, int *khz)
{
    *khz = speed;
    return ERROR_OK;
}
 
static int cmsis_dap_khz(int khz, int *jtag_speed)
{
    *jtag_speed = khz;
    return ERROR_OK;
}
 
static bool calculate_swo_prescaler(unsigned int traceclkin_freq,
        uint32_t trace_freq, uint16_t *prescaler)
{
    unsigned int presc = (traceclkin_freq + trace_freq / 2) / trace_freq;
    if (presc == 0 || presc > TPIU_ACPR_MAX_SWOSCALER + 1)
        return false;
 
    /* Probe's UART speed must be within 3% of the TPIU's SWO baud rate. */
    unsigned int max_deviation = (traceclkin_freq * 3) / 100;
    if (presc * trace_freq < traceclkin_freq - max_deviation ||
        presc * trace_freq > traceclkin_freq + max_deviation)
        return false;
 
    *prescaler = presc;
 
    return true;
}
 
static int cmsis_dap_config_trace(
                bool trace_enabled,
                enum tpiu_pin_protocol pin_protocol,
                uint32_t port_size,
                unsigned int *swo_freq,
                unsigned int traceclkin_hz,
                uint16_t *swo_prescaler)
{
    int retval;
 
    if (!trace_enabled) {
        if (cmsis_dap_handle->trace_enabled) {
            retval = cmsis_dap_cmd_dap_swo_control(DAP_SWO_CONTROL_STOP);
            if (retval != ERROR_OK) {
                LOG_ERROR("Failed to disable the SWO-trace.");
                return retval;
            }
        }
        cmsis_dap_handle->trace_enabled = false;
        LOG_INFO("SWO-trace disabled.");
        return ERROR_OK;
    }
 
    if (!(cmsis_dap_handle->caps & INFO_CAPS_SWO_UART) &&
        !(cmsis_dap_handle->caps & INFO_CAPS_SWO_MANCHESTER)) {
        LOG_ERROR("SWO-trace is not supported by the device.");
        return ERROR_FAIL;
    }
 
    uint8_t swo_mode;
    if (pin_protocol == TPIU_PIN_PROTOCOL_ASYNC_UART &&
       (cmsis_dap_handle->caps & INFO_CAPS_SWO_UART)) {
        swo_mode = DAP_SWO_MODE_UART;
    } else if (pin_protocol == TPIU_PIN_PROTOCOL_ASYNC_MANCHESTER &&
          (cmsis_dap_handle->caps & INFO_CAPS_SWO_MANCHESTER)) {
        swo_mode = DAP_SWO_MODE_MANCHESTER;
    } else {
        LOG_ERROR("Selected pin protocol is not supported.");
        return ERROR_FAIL;
    }
 
    if (*swo_freq == 0) {
        LOG_INFO("SWO-trace frequency autodetection not implemented.");
        return ERROR_FAIL;
    }
 
    retval = cmsis_dap_cmd_dap_swo_control(DAP_SWO_CONTROL_STOP);
    if (retval != ERROR_OK)
        return retval;
 
    cmsis_dap_handle->trace_enabled = false;
 
    retval = cmsis_dap_get_swo_buf_sz(&cmsis_dap_handle->swo_buf_sz);
    if (retval != ERROR_OK)
        return retval;
 
    retval = cmsis_dap_cmd_dap_swo_transport(DAP_SWO_TRANSPORT_DATA);
    if (retval != ERROR_OK)
        return retval;
 
    retval = cmsis_dap_cmd_dap_swo_mode(swo_mode);
    if (retval != ERROR_OK)
        return retval;
 
    retval = cmsis_dap_cmd_dap_swo_baudrate(*swo_freq, swo_freq);
    if (retval != ERROR_OK)
        return retval;
 
    if (!calculate_swo_prescaler(traceclkin_hz, *swo_freq,
            swo_prescaler)) {
        LOG_ERROR("SWO frequency is not suitable. Please choose a "
            "different frequency or use auto-detection.");
        return ERROR_FAIL;
    }
 
    LOG_INFO("SWO frequency: %u Hz.", *swo_freq);
    LOG_INFO("SWO prescaler: %u.", *swo_prescaler);
 
    retval = cmsis_dap_cmd_dap_swo_control(DAP_SWO_CONTROL_START);
    if (retval != ERROR_OK)
        return retval;
 
    cmsis_dap_handle->trace_enabled = true;
 
    return ERROR_OK;
}
 
static int cmsis_dap_poll_trace(uint8_t *buf, size_t *size)
{
    uint8_t trace_status;
    size_t trace_count;
 
    if (!cmsis_dap_handle->trace_enabled) {
        *size = 0;
        return ERROR_OK;
    }
 
    int retval = cmsis_dap_cmd_dap_swo_status(&trace_status, &trace_count);
    if (retval != ERROR_OK)
        return retval;
    if ((trace_status & DAP_SWO_STATUS_CAPTURE_MASK) != DAP_SWO_STATUS_CAPTURE_ACTIVE)
        return ERROR_FAIL;
 
    *size = trace_count < *size ? trace_count : *size;
    size_t read_so_far = 0;
    do {
        size_t rb = 0;
        uint32_t packet_size = cmsis_dap_handle->packet_size - 4 /*data-reply*/;
        uint32_t remaining = *size - read_so_far;
        if (remaining < packet_size)
            packet_size = remaining;
        retval = cmsis_dap_cmd_dap_swo_data(
                        packet_size,
                        &trace_status,
                        &rb,
                        &buf[read_so_far]);
        if (retval != ERROR_OK)
            return retval;
        if ((trace_status & DAP_SWO_STATUS_CAPTURE_MASK) != DAP_SWO_STATUS_CAPTURE_ACTIVE)
            return ERROR_FAIL;
 
        read_so_far += rb;
    } while (read_so_far < *size);
 
    return ERROR_OK;
}
 
COMMAND_HANDLER(cmsis_dap_handle_info_command)
{
    if (cmsis_dap_get_version_info() == ERROR_OK)
        cmsis_dap_get_status();
 
    return ERROR_OK;
}
 
COMMAND_HANDLER(cmsis_dap_handle_cmd_command)
{
    uint8_t *command = cmsis_dap_handle->command;
 
    for (unsigned int i = 0; i < CMD_ARGC; i++)
        COMMAND_PARSE_NUMBER(u8, CMD_ARGV[i], command[i]);
 
    int retval = cmsis_dap_xfer(cmsis_dap_handle, CMD_ARGC);
 
    if (retval != ERROR_OK) {
        LOG_ERROR("CMSIS-DAP command failed.");
        return ERROR_JTAG_DEVICE_ERROR;
    }
 
    uint8_t *resp = cmsis_dap_handle->response;
    LOG_INFO("Returned data %02" PRIx8 " %02" PRIx8 " %02" PRIx8 " %02" PRIx8,
        resp[1], resp[2], resp[3], resp[4]);
 
    return ERROR_OK;
}
 
COMMAND_HANDLER(cmsis_dap_handle_vid_pid_command)
{
    if (CMD_ARGC > MAX_USB_IDS * 2) {
        LOG_WARNING("ignoring extra IDs in cmsis-dap vid_pid "
            "(maximum is %d pairs)", MAX_USB_IDS);
        CMD_ARGC = MAX_USB_IDS * 2;
    }
    if (CMD_ARGC < 2 || (CMD_ARGC & 1)) {
        LOG_WARNING("incomplete cmsis-dap vid_pid configuration directive");
        if (CMD_ARGC < 2)
            return ERROR_COMMAND_SYNTAX_ERROR;
        /* remove the incomplete trailing id */
        CMD_ARGC -= 1;
    }
 
    unsigned int i;
    for (i = 0; i < CMD_ARGC; i += 2) {
        COMMAND_PARSE_NUMBER(u16, CMD_ARGV[i], cmsis_dap_vid[i >> 1]);
        COMMAND_PARSE_NUMBER(u16, CMD_ARGV[i + 1], cmsis_dap_pid[i >> 1]);
    }
 
    /*
     * Explicitly terminate, in case there are multiples instances of
     * cmsis_dap_vid_pid.
     */
    cmsis_dap_vid[i >> 1] = cmsis_dap_pid[i >> 1] = 0;
 
    return ERROR_OK;
}
 
COMMAND_HANDLER(cmsis_dap_handle_backend_command)
{
    if (CMD_ARGC != 1)
        return ERROR_COMMAND_SYNTAX_ERROR;
 
    if (strcmp(CMD_ARGV[0], "auto") == 0) {
        cmsis_dap_backend = -1; /* autoselect */
    } else {
        for (unsigned int i = 0; i < ARRAY_SIZE(cmsis_dap_backends); i++) {
            if (strcasecmp(cmsis_dap_backends[i]->name, CMD_ARGV[0]) == 0) {
                if (cmsis_dap_backends[i]->open) {
                    cmsis_dap_backend = i;
                    return ERROR_OK;
                }
 
                command_print(CMD, "Requested cmsis-dap backend %s is disabled by configure",
                              cmsis_dap_backends[i]->name);
                return ERROR_NOT_IMPLEMENTED;
            }
        }
 
        command_print(CMD, "invalid argument %s to cmsis-dap backend", CMD_ARGV[0]);
        return ERROR_COMMAND_ARGUMENT_INVALID;
    }
 
    return ERROR_OK;
}
 
COMMAND_HANDLER(cmsis_dap_handle_quirk_command)
{
    if (CMD_ARGC > 1)
        return ERROR_COMMAND_SYNTAX_ERROR;
 
    if (CMD_ARGC == 1) {
        COMMAND_PARSE_ENABLE(CMD_ARGV[0], cmsis_dap_quirk_mode);
        return ERROR_OK;
    }
 
    command_print(CMD, "%s", cmsis_dap_quirk_mode ? "enabled" : "disabled");
 
    return ERROR_OK;
}
 
static const struct command_registration cmsis_dap_subcommand_handlers[] = {
    {
        .name = "info",
        .handler = &cmsis_dap_handle_info_command,
        .mode = COMMAND_EXEC,
        .usage = "",
        .help = "show cmsis-dap info",
    },
    {
        .name = "cmd",
        .handler = &cmsis_dap_handle_cmd_command,
        .mode = COMMAND_EXEC,
        .usage = "",
        .help = "issue cmsis-dap command",
    },
    {
        .name = "vid_pid",
        .handler = &cmsis_dap_handle_vid_pid_command,
        .mode = COMMAND_CONFIG,
        .help = "the vendor ID and product ID of the CMSIS-DAP device",
        .usage = "(vid pid)*",
    },
    {
        .name = "backend",
        .handler = &cmsis_dap_handle_backend_command,
        .mode = COMMAND_CONFIG,
        .help = "set the communication backend to use (USB bulk or HID, or TCP).",
        .usage = "(auto | usb_bulk | hid | tcp)",
    },
    {
        .name = "quirk",
        .handler = &cmsis_dap_handle_quirk_command,
        .mode = COMMAND_ANY,
        .help = "allow expensive workarounds of known adapter quirks.",
        .usage = "[enable | disable]",
    },
#if BUILD_CMSIS_DAP_USB
    {
        .name = "usb",
        .chain = cmsis_dap_usb_subcommand_handlers,
        .mode = COMMAND_ANY,
        .help = "USB bulk backend-specific commands",
        .usage = "<cmd>",
    },
#endif
#if BUILD_CMSIS_DAP_TCP
    {
        .name = "tcp",
        .chain = cmsis_dap_tcp_subcommand_handlers,
        .mode = COMMAND_ANY,
        .help = "TCP backend-specific commands",
        .usage = "<cmd>",
    },
#endif
    COMMAND_REGISTRATION_DONE
};
 
 
static const struct command_registration cmsis_dap_command_handlers[] = {
    {
        .name = "cmsis-dap",
        .mode = COMMAND_ANY,
        .help = "perform CMSIS-DAP management",
        .usage = "<cmd>",
        .chain = cmsis_dap_subcommand_handlers,
    },
    COMMAND_REGISTRATION_DONE
};
 
static const struct swd_driver cmsis_dap_swd_driver = {
    .init = cmsis_dap_swd_init,
    .switch_seq = cmsis_dap_swd_switch_seq,
    .read_reg = cmsis_dap_swd_read_reg,
    .write_reg = cmsis_dap_swd_write_reg,
    .run = cmsis_dap_swd_run_queue,
};
 
static struct jtag_interface cmsis_dap_interface = {
    .supported = DEBUG_CAP_TMS_SEQ,
    .execute_queue = cmsis_dap_execute_queue,
};
 
struct adapter_driver cmsis_dap_adapter_driver = {
    .name = "cmsis-dap",
    .transport_ids = TRANSPORT_SWD | TRANSPORT_JTAG,
    .transport_preferred_id = TRANSPORT_SWD,
    .commands = cmsis_dap_command_handlers,
 
    .init = cmsis_dap_init,
    .quit = cmsis_dap_quit,
    .reset = cmsis_dap_reset,
    .speed = cmsis_dap_speed,
    .khz = cmsis_dap_khz,
    .speed_div = cmsis_dap_speed_div,
    .config_trace = cmsis_dap_config_trace,
    .poll_trace = cmsis_dap_poll_trace,
 
    .jtag_ops = &cmsis_dap_interface,
    .swd_ops = &cmsis_dap_swd_driver,
};