sysfsgpio.c

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// SPDX-License-Identifier: GPL-2.0-or-later
 
/***************************************************************************
 *   Copyright (C) 2012 by Creative Product Design, marc @ cpdesign.com.au *
 ***************************************************************************/
 
/* 2014-12: Addition of the SWD protocol support is based on the initial work
 * on bcm2835gpio.c by Paul Fertser and modifications by Jean-Christian de Rivaz. */
 
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
 
#include <helper/time_support.h>
#include <jtag/interface.h>
#include <transport/transport.h>
#include "bitbang.h"
 
/*
 * Helper func to determine if gpio number valid
 *
 * Assume here that there will be less than 10000 gpios on a system
 */
static bool is_gpio_valid(int gpio)
{
    return gpio >= 0 && gpio < 10000;
}
 
/*
 * Helper func to open, write to and close a file
 * name and valstr must be null terminated.
 *
 * Returns negative on failure.
 */
static int open_write_close(const char *name, const char *valstr)
{
    int ret;
    int fd = open(name, O_WRONLY);
    if (fd < 0)
        return fd;
 
    ret = write(fd, valstr, strlen(valstr));
    close(fd);
 
    return ret;
}
 
/*
 * Helper func to unexport gpio from sysfs
 */
static void unexport_sysfs_gpio(int gpio)
{
    char gpiostr[5];
 
    if (!is_gpio_valid(gpio))
        return;
 
    snprintf(gpiostr, sizeof(gpiostr), "%d", gpio);
    if (open_write_close("/sys/class/gpio/unexport", gpiostr) < 0)
        LOG_ERROR("Couldn't unexport gpio %d", gpio);
}
 
/*
 * Exports and sets up direction for gpio.
 * If the gpio is an output, it is initialized according to init_high,
 * otherwise it is ignored.
 *
 * If the gpio is already exported we just show a warning and continue; if
 * openocd happened to crash (or was killed by user) then the gpios will not
 * have been cleaned up.
 */
static int setup_sysfs_gpio(int gpio, int is_output, int init_high)
{
    char buf[40];
    char gpiostr[5];
    int ret;
 
    if (!is_gpio_valid(gpio))
        return ERROR_OK;
 
    snprintf(gpiostr, sizeof(gpiostr), "%d", gpio);
    ret = open_write_close("/sys/class/gpio/export", gpiostr);
    if (ret < 0) {
        if (errno == EBUSY) {
            LOG_WARNING("gpio %d is already exported", gpio);
        } else {
            LOG_ERROR("Couldn't export gpio %d", gpio);
            LOG_ERROR("sysfsgpio: %s", strerror(errno));
            return ERROR_FAIL;
        }
    }
 
    // 500 ms timeout
    int64_t then = timeval_ms() + 500;
 
    snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/direction", gpio);
    for (;;) {
        ret = open_write_close(buf, is_output ? (init_high ? "high" : "low") : "in");
        if (ret >= 0 || errno != EACCES)
            break;
        if (timeval_ms() >= then)
            break;
        jtag_sleep(10000);
    }
    if (ret < 0) {
        LOG_ERROR("Couldn't set direction for gpio %d", gpio);
        LOG_ERROR("sysfsgpio: %s", strerror(errno));
        unexport_sysfs_gpio(gpio);
        return ERROR_FAIL;
    }
 
    snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/value", gpio);
    for (;;) {
        ret = open(buf, O_RDWR | O_NONBLOCK | O_SYNC);
        if (ret >= 0 || errno != EACCES)
            break;
        if (timeval_ms() >= then)
            break;
        jtag_sleep(10000);
    }
    if (ret < 0) {
        LOG_ERROR("Couldn't open value for gpio %d", gpio);
        LOG_ERROR("sysfsgpio: %s", strerror(errno));
        unexport_sysfs_gpio(gpio);
    }
 
    return ret;
}
 
/* gpio numbers for each gpio. Negative values are invalid */
static int tck_gpio = -1;
static int tms_gpio = -1;
static int tdi_gpio = -1;
static int tdo_gpio = -1;
static int trst_gpio = -1;
static int srst_gpio = -1;
static int swclk_gpio = -1;
static int swdio_gpio = -1;
 
/*
 * file descriptors for /sys/class/gpio/gpioXX/value
 * Set up during init.
 */
static int tck_fd = -1;
static int tms_fd = -1;
static int tdi_fd = -1;
static int tdo_fd = -1;
static int trst_fd = -1;
static int srst_fd = -1;
static int swclk_fd = -1;
static int swdio_fd = -1;
 
static int last_swclk;
static int last_swdio;
static bool last_stored;
static bool swdio_input;
 
static void sysfsgpio_swdio_drive(bool is_output)
{
    char buf[40];
    int ret;
 
    snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/direction", swdio_gpio);
    ret = open_write_close(buf, is_output ? "high" : "in");
    if (ret < 0) {
        LOG_ERROR("Couldn't set direction for gpio %d", swdio_gpio);
        LOG_ERROR("sysfsgpio: %s", strerror(errno));
    }
 
    last_stored = false;
    swdio_input = !is_output;
}
 
static int sysfsgpio_swdio_read(void)
{
    char buf[1];
 
    /* important to seek to signal sysfs of new read */
    lseek(swdio_fd, 0, SEEK_SET);
    int ret = read(swdio_fd, &buf, sizeof(buf));
 
    if (ret < 0) {
        LOG_WARNING("reading swdio failed");
        return 0;
    }
 
    return buf[0] != '0';
}
 
static int sysfsgpio_swd_write(int swclk, int swdio)
{
    const char one[] = "1";
    const char zero[] = "0";
 
    size_t bytes_written;
 
    if (!swdio_input) {
        if (!last_stored || (swdio != last_swdio)) {
            bytes_written = write(swdio_fd, swdio ? &one : &zero, 1);
            if (bytes_written != 1)
                LOG_WARNING("writing swdio failed");
        }
    }
 
    /* write swclk last */
    if (!last_stored || (swclk != last_swclk)) {
        bytes_written = write(swclk_fd, swclk ? &one : &zero, 1);
        if (bytes_written != 1)
            LOG_WARNING("writing swclk failed");
    }
 
    last_swdio = swdio;
    last_swclk = swclk;
    last_stored = true;
 
    return ERROR_OK;
}
 
/*
 * Bitbang interface read of TDO
 *
 * The sysfs value will read back either '0' or '1'. The trick here is to call
 * lseek to bypass buffering in the sysfs kernel driver.
 */
static enum bb_value sysfsgpio_read(void)
{
    char buf[1];
 
    /* important to seek to signal sysfs of new read */
    lseek(tdo_fd, 0, SEEK_SET);
    int ret = read(tdo_fd, &buf, sizeof(buf));
 
    if (ret < 0) {
        LOG_WARNING("reading tdo failed");
        return 0;
    }
 
    return buf[0] == '0' ? BB_LOW : BB_HIGH;
}
 
/*
 * Bitbang interface write of TCK, TMS, TDI
 *
 * Seeing as this is the only function where the outputs are changed,
 * we can cache the old value to avoid needlessly writing it.
 */
static int sysfsgpio_write(int tck, int tms, int tdi)
{
    const char one[] = "1";
    const char zero[] = "0";
 
    static int last_tck;
    static int last_tms;
    static int last_tdi;
 
    static int first_time;
    size_t bytes_written;
 
    if (!first_time) {
        last_tck = !tck;
        last_tms = !tms;
        last_tdi = !tdi;
        first_time = 1;
    }
 
    if (tdi != last_tdi) {
        bytes_written = write(tdi_fd, tdi ? &one : &zero, 1);
        if (bytes_written != 1)
            LOG_WARNING("writing tdi failed");
    }
 
    if (tms != last_tms) {
        bytes_written = write(tms_fd, tms ? &one : &zero, 1);
        if (bytes_written != 1)
            LOG_WARNING("writing tms failed");
    }
 
    /* write clk last */
    if (tck != last_tck) {
        bytes_written = write(tck_fd, tck ? &one : &zero, 1);
        if (bytes_written != 1)
            LOG_WARNING("writing tck failed");
    }
 
    last_tdi = tdi;
    last_tms = tms;
    last_tck = tck;
 
    return ERROR_OK;
}
 
/*
 * Bitbang interface to manipulate reset lines SRST and TRST
 *
 * (1) assert or (0) deassert reset lines
 */
static int sysfsgpio_reset(int trst, int srst)
{
    LOG_DEBUG("sysfsgpio_reset");
    const char one[] = "1";
    const char zero[] = "0";
    size_t bytes_written;
 
    /* assume active low */
    if (srst_fd >= 0) {
        bytes_written = write(srst_fd, srst ? &zero : &one, 1);
        if (bytes_written != 1)
            LOG_WARNING("writing srst failed");
    }
 
    /* assume active low */
    if (trst_fd >= 0) {
        bytes_written = write(trst_fd, trst ? &zero : &one, 1);
        if (bytes_written != 1)
            LOG_WARNING("writing trst failed");
    }
 
    return ERROR_OK;
}
 
COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionums)
{
    if (CMD_ARGC == 4) {
        COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tck_gpio);
        COMMAND_PARSE_NUMBER(int, CMD_ARGV[1], tms_gpio);
        COMMAND_PARSE_NUMBER(int, CMD_ARGV[2], tdi_gpio);
        COMMAND_PARSE_NUMBER(int, CMD_ARGV[3], tdo_gpio);
    } else if (CMD_ARGC != 0) {
        return ERROR_COMMAND_SYNTAX_ERROR;
    }
 
    command_print(CMD,
            "SysfsGPIO nums: tck = %d, tms = %d, tdi = %d, tdo = %d",
            tck_gpio, tms_gpio, tdi_gpio, tdo_gpio);
 
    return ERROR_OK;
}
 
COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tck)
{
    if (CMD_ARGC == 1)
        COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tck_gpio);
 
    command_print(CMD, "SysfsGPIO num: tck = %d", tck_gpio);
    return ERROR_OK;
}
 
COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tms)
{
    if (CMD_ARGC == 1)
        COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tms_gpio);
 
    command_print(CMD, "SysfsGPIO num: tms = %d", tms_gpio);
    return ERROR_OK;
}
 
COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tdo)
{
    if (CMD_ARGC == 1)
        COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tdo_gpio);
 
    command_print(CMD, "SysfsGPIO num: tdo = %d", tdo_gpio);
    return ERROR_OK;
}
 
COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_tdi)
{
    if (CMD_ARGC == 1)
        COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], tdi_gpio);
 
    command_print(CMD, "SysfsGPIO num: tdi = %d", tdi_gpio);
    return ERROR_OK;
}
 
COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_srst)
{
    if (CMD_ARGC == 1)
        COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], srst_gpio);
 
    command_print(CMD, "SysfsGPIO num: srst = %d", srst_gpio);
    return ERROR_OK;
}
 
COMMAND_HANDLER(sysfsgpio_handle_jtag_gpionum_trst)
{
    if (CMD_ARGC == 1)
        COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], trst_gpio);
 
    command_print(CMD, "SysfsGPIO num: trst = %d", trst_gpio);
    return ERROR_OK;
}
 
COMMAND_HANDLER(sysfsgpio_handle_swd_gpionums)
{
    if (CMD_ARGC == 2) {
        COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], swclk_gpio);
        COMMAND_PARSE_NUMBER(int, CMD_ARGV[1], swdio_gpio);
    } else if (CMD_ARGC != 0) {
        return ERROR_COMMAND_SYNTAX_ERROR;
    }
 
    command_print(CMD,
            "SysfsGPIO nums: swclk = %d, swdio = %d",
            swclk_gpio, swdio_gpio);
 
    return ERROR_OK;
}
 
COMMAND_HANDLER(sysfsgpio_handle_swd_gpionum_swclk)
{
    if (CMD_ARGC == 1)
        COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], swclk_gpio);
 
    command_print(CMD, "SysfsGPIO num: swclk = %d", swclk_gpio);
    return ERROR_OK;
}
 
COMMAND_HANDLER(sysfsgpio_handle_swd_gpionum_swdio)
{
    if (CMD_ARGC == 1)
        COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], swdio_gpio);
 
    command_print(CMD, "SysfsGPIO num: swdio = %d", swdio_gpio);
    return ERROR_OK;
}
 
static const struct command_registration sysfsgpio_subcommand_handlers[] = {
    {
        .name = "jtag_nums",
        .handler = &sysfsgpio_handle_jtag_gpionums,
        .mode = COMMAND_CONFIG,
        .help = "gpio numbers for tck, tms, tdi, tdo. (in that order)",
        .usage = "[tck tms tdi tdo]",
    },
    {
        .name = "tck_num",
        .handler = &sysfsgpio_handle_jtag_gpionum_tck,
        .mode = COMMAND_CONFIG,
        .help = "gpio number for tck.",
        .usage = "[tck]",
    },
    {
        .name = "tms_num",
        .handler = &sysfsgpio_handle_jtag_gpionum_tms,
        .mode = COMMAND_CONFIG,
        .help = "gpio number for tms.",
        .usage = "[tms]",
    },
    {
        .name = "tdo_num",
        .handler = &sysfsgpio_handle_jtag_gpionum_tdo,
        .mode = COMMAND_CONFIG,
        .help = "gpio number for tdo.",
        .usage = "[tdo]",
    },
    {
        .name = "tdi_num",
        .handler = &sysfsgpio_handle_jtag_gpionum_tdi,
        .mode = COMMAND_CONFIG,
        .help = "gpio number for tdi.",
        .usage = "[tdi]",
    },
    {
        .name = "srst_num",
        .handler = &sysfsgpio_handle_jtag_gpionum_srst,
        .mode = COMMAND_CONFIG,
        .help = "gpio number for srst.",
        .usage = "[srst]",
    },
    {
        .name = "trst_num",
        .handler = &sysfsgpio_handle_jtag_gpionum_trst,
        .mode = COMMAND_CONFIG,
        .help = "gpio number for trst.",
        .usage = "[trst]",
    },
    {
        .name = "swd_nums",
        .handler = &sysfsgpio_handle_swd_gpionums,
        .mode = COMMAND_CONFIG,
        .help = "gpio numbers for swclk, swdio. (in that order)",
        .usage = "[swclk swdio]",
    },
    {
        .name = "swclk_num",
        .handler = &sysfsgpio_handle_swd_gpionum_swclk,
        .mode = COMMAND_CONFIG,
        .help = "gpio number for swclk.",
        .usage = "[swclk]",
    },
    {
        .name = "swdio_num",
        .handler = &sysfsgpio_handle_swd_gpionum_swdio,
        .mode = COMMAND_CONFIG,
        .help = "gpio number for swdio.",
        .usage = "[swdio]",
    },
    COMMAND_REGISTRATION_DONE
};
 
static const struct command_registration sysfsgpio_command_handlers[] = {
    {
        .name = "sysfsgpio",
        .mode = COMMAND_ANY,
        .help = "perform sysfsgpio management",
        .chain = sysfsgpio_subcommand_handlers,
        .usage = "",
    },
    COMMAND_REGISTRATION_DONE
};
 
static int sysfsgpio_init(void);
static int sysfsgpio_quit(void);
 
static struct jtag_interface sysfsgpio_interface = {
    .supported = DEBUG_CAP_TMS_SEQ,
    .execute_queue = bitbang_execute_queue,
};
 
struct adapter_driver sysfsgpio_adapter_driver = {
    .name = "sysfsgpio",
    .transport_ids = TRANSPORT_JTAG | TRANSPORT_SWD,
    .transport_preferred_id = TRANSPORT_JTAG,
    .commands = sysfsgpio_command_handlers,
 
    .init = sysfsgpio_init,
    .quit = sysfsgpio_quit,
    .reset = sysfsgpio_reset,
 
    .jtag_ops = &sysfsgpio_interface,
    .swd_ops = &bitbang_swd,
};
 
static const struct bitbang_interface sysfsgpio_bitbang = {
    .read = sysfsgpio_read,
    .write = sysfsgpio_write,
    .swdio_read = sysfsgpio_swdio_read,
    .swdio_drive = sysfsgpio_swdio_drive,
    .swd_write = sysfsgpio_swd_write,
    .blink = NULL,
};
 
/* helper func to close and cleanup files only if they were valid/ used */
static void cleanup_fd(int fd, int gpio)
{
    if (gpio >= 0) {
        if (fd >= 0)
            close(fd);
 
        unexport_sysfs_gpio(gpio);
    }
}
 
static void cleanup_all_fds(void)
{
    if (transport_is_jtag()) {
        cleanup_fd(tck_fd, tck_gpio);
        cleanup_fd(tms_fd, tms_gpio);
        cleanup_fd(tdi_fd, tdi_gpio);
        cleanup_fd(tdo_fd, tdo_gpio);
        cleanup_fd(trst_fd, trst_gpio);
    }
    if (transport_is_swd()) {
        cleanup_fd(swclk_fd, swclk_gpio);
        cleanup_fd(swdio_fd, swdio_gpio);
    }
    cleanup_fd(srst_fd, srst_gpio);
}
 
static bool sysfsgpio_jtag_mode_possible(void)
{
    if (!is_gpio_valid(tck_gpio))
        return false;
    if (!is_gpio_valid(tms_gpio))
        return false;
    if (!is_gpio_valid(tdi_gpio))
        return false;
    if (!is_gpio_valid(tdo_gpio))
        return false;
    return true;
}
 
static bool sysfsgpio_swd_mode_possible(void)
{
    if (!is_gpio_valid(swclk_gpio))
        return false;
    if (!is_gpio_valid(swdio_gpio))
        return false;
    return true;
}
 
static int sysfsgpio_init(void)
{
    bitbang_interface = &sysfsgpio_bitbang;
 
    LOG_INFO("SysfsGPIO JTAG/SWD bitbang driver");
 
    /*
     * Configure TDO as an input, and TDI, TCK, TMS, TRST, SRST
     * as outputs.  Drive TDI and TCK low, and TMS/TRST/SRST high.
     * For SWD, SWCLK and SWDIO are configures as output high.
     */
 
    if (transport_is_jtag()) {
        if (!sysfsgpio_jtag_mode_possible()) {
            LOG_ERROR("Require tck, tms, tdi and tdo gpios for JTAG mode");
            return ERROR_JTAG_INIT_FAILED;
        }
 
        tck_fd = setup_sysfs_gpio(tck_gpio, 1, 0);
        if (tck_fd < 0)
            goto out_error;
 
        tms_fd = setup_sysfs_gpio(tms_gpio, 1, 1);
        if (tms_fd < 0)
            goto out_error;
 
        tdi_fd = setup_sysfs_gpio(tdi_gpio, 1, 0);
        if (tdi_fd < 0)
            goto out_error;
 
        tdo_fd = setup_sysfs_gpio(tdo_gpio, 0, 0);
        if (tdo_fd < 0)
            goto out_error;
 
        /* assume active low*/
        if (trst_gpio >= 0) {
            trst_fd = setup_sysfs_gpio(trst_gpio, 1, 1);
            if (trst_fd < 0)
                goto out_error;
        }
    }
 
    if (transport_is_swd()) {
        if (!sysfsgpio_swd_mode_possible()) {
            LOG_ERROR("Require swclk and swdio gpio for SWD mode");
            return ERROR_JTAG_INIT_FAILED;
        }
 
        swclk_fd = setup_sysfs_gpio(swclk_gpio, 1, 0);
        if (swclk_fd < 0)
            goto out_error;
 
        swdio_fd = setup_sysfs_gpio(swdio_gpio, 1, 0);
        if (swdio_fd < 0)
            goto out_error;
    }
 
    /* assume active low*/
    if (srst_gpio >= 0) {
        srst_fd = setup_sysfs_gpio(srst_gpio, 1, 1);
        if (srst_fd < 0)
            goto out_error;
    }
 
    return ERROR_OK;
 
out_error:
    cleanup_all_fds();
    return ERROR_JTAG_INIT_FAILED;
}
 
static int sysfsgpio_quit(void)
{
    cleanup_all_fds();
    return ERROR_OK;
}