drivers: new jtag bitbang driver using sysfs gpio

[openocd.git] / src / jtag / drivers / sysfsgpio.c

/***************************************************************************
 *   Copyright (C) 2012 by Creative Product Design, marc @ cpdesign.com.au *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/
/**
 * @file
 * This driver implements a bitbang jtag interface using gpio lines via
 * sysfs.
 * The aim of this driver implementation is use system GPIOs but avoid the
 * need for a additional kernel driver.
 * (Note memory mapped IO is another option, however it doesn't mix well with
 * the kernel gpiolib driver - which makes sense I guess.)
 *
 * A gpio is required for tck, tms, tdi and tdo. One or both of srst and trst
 * must be also be specified. The required jtag gpios are specified via the
 * sysfsgpio_jtag_nums command or the relevant sysfsgpio_XXX_num commang.
 * The srst and trst gpios are set via the sysfsgpio_srst_num and
 * sysfsgpio_trst_num respectively. GPIO numbering follows the kernel
 * convention of starting from 0.
 *
 * The gpios should not be in use by another entity, and must not be requested
 * by a kernel driver without also being exported by it (otherwise they can't
 * be exported by sysfs).
 *
 * The sysfs gpio interface can only manipulate one gpio at a time, so the
 * bitbang write handler remembers the last state for tck, tms, tdi to avoid
 * superfluous writes.
 * For speed the sysfs "value" entry is opened at init and held open.
 * This results in considerable gains over open-write-close (45s vs 900s)
 *
 * Further work could address:
 *  -srst and trst open drain/ push pull
 *  -configurable active high/low for srst & trst
 */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <jtag/interface.h>
#include "bitbang.h"

/*
 * Helper func to determine if gpio number valid
 *
 * Assume here that there will be less than 1000 gpios on a system
 */
static int is_gpio_valid(int gpio)
{
        return gpio >= 0 && gpio < 1000;
}

/*
 * 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[4];

        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);

        return;
}

/*
 * 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[4];
        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);
                        perror("sysfsgpio: ");
                        return ERROR_FAIL;
                }
        }

        snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/direction", gpio);
        ret = open_write_close(buf, is_output ? (init_high ? "high" : "low") : "in");
        if (ret < 0) {
                LOG_ERROR("Couldn't set direction for gpio %d", gpio);
                perror("sysfsgpio: ");
                unexport_sysfs_gpio(gpio);
                return ERROR_FAIL;
        }

        snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/value", gpio);
        if (is_output)
                ret = open(buf, O_WRONLY | O_NONBLOCK | O_SYNC);
        else
                ret = open(buf, O_RDONLY | O_NONBLOCK | O_SYNC);

        if (ret < 0)
                unexport_sysfs_gpio(gpio);

        return ret;
}

/*
 * 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;

/*
 * 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 int 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] == '1';
}

/*
 * 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 void 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;

        if (!first_time) {
                last_tck = !tck;
                last_tms = !tms;
                last_tdi = !tdi;
                first_time = 1;
        }

        if (tdi != last_tdi)
                write(tdi_fd, tdi ? &one : &zero, 1);
        if (tms != last_tms)
                write(tms_fd, tms ? &one : &zero, 1);
        /* write clk last */
        if (tck != last_tck)
                write(tck_fd, tck ? &one : &zero, 1);

        last_tdi = tdi;
        last_tms = tms;
        last_tck = tck;
}

/*
 * Bitbang interface to manipulate reset lines SRST and TRST
 *
 * (1) assert or (0) deassert reset lines
 */
static void sysfsgpio_reset(int trst, int srst)
{
        const char one[] = "1";
        const char zero[] = "0";

        /* assume active low */
        if (srst_fd >= 0)
                write(srst_fd, srst ? &zero : &one, 1);

        /* assume active low */
        if (trst_fd >= 0)
                write(trst_fd, trst ? &zero : &one, 1);
}

/* No speed control is implemented yet */
static int sysfsgpio_speed(int speed)
{
        return ERROR_OK;
}

static int sysfsgpio_khz(int khz, int *jtag_speed)
{
        /* no adaptive clocking */
        if (khz == 0)
                return ERROR_FAIL;

        *jtag_speed = 0;
        return ERROR_OK;
}

static int sysfsgpio_speed_div(int speed, int *khz)
{
        *khz = 1;
        return ERROR_OK;
}

/* 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;

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_CTX,
                        "SysfsGPIO nums: tck = %d, tms = %d, tdi = %d, tdi = %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_CTX, "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_CTX, "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_CTX, "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_CTX, "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_CTX, "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_CTX, "SysfsGPIO num: trst = %d", trst_gpio);
        return ERROR_OK;
}

static const struct command_registration sysfsgpio_command_handlers[] = {
        {
                .name = "sysfsgpio_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 = "sysfsgpio_tck_num",
                .handler = &sysfsgpio_handle_jtag_gpionum_tck,
                .mode = COMMAND_CONFIG,
                .help = "gpio number for tck.",
        },
        {
                .name = "sysfsgpio_tms_num",
                .handler = &sysfsgpio_handle_jtag_gpionum_tms,
                .mode = COMMAND_CONFIG,
                .help = "gpio number for tms.",
        },
        {
                .name = "sysfsgpio_tdo_num",
                .handler = &sysfsgpio_handle_jtag_gpionum_tdo,
                .mode = COMMAND_CONFIG,
                .help = "gpio number for tdo.",
        },
        {
                .name = "sysfsgpio_tdi_num",
                .handler = &sysfsgpio_handle_jtag_gpionum_tdi,
                .mode = COMMAND_CONFIG,
                .help = "gpio number for tdi.",
        },
        {
                .name = "sysfsgpio_srst_num",
                .handler = &sysfsgpio_handle_jtag_gpionum_srst,
                .mode = COMMAND_CONFIG,
                .help = "gpio number for srst.",
        },
        {
                .name = "sysfsgpio_trst_num",
                .handler = &sysfsgpio_handle_jtag_gpionum_trst,
                .mode = COMMAND_CONFIG,
                .help = "gpio number for trst.",
        },
        COMMAND_REGISTRATION_DONE
};

static int sysfsgpio_init(void);
static int sysfsgpio_quit(void);

struct jtag_interface sysfsgpio_interface = {
        .name = "sysfsgpio",
        .supported = DEBUG_CAP_TMS_SEQ,
        .execute_queue = bitbang_execute_queue,
        .transports = jtag_only,
        .speed = sysfsgpio_speed,
        .khz = sysfsgpio_khz,
        .speed_div = sysfsgpio_speed_div,
        .commands = sysfsgpio_command_handlers,
        .init = sysfsgpio_init,
        .quit = sysfsgpio_quit,
};

static struct bitbang_interface sysfsgpio_bitbang = {
        .read = sysfsgpio_read,
        .write = sysfsgpio_write,
        .reset = sysfsgpio_reset,
        .blink = 0
};

/* 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)
{
        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);
        cleanup_fd(srst_fd, srst_gpio);
}

static int sysfsgpio_init(void)
{
        bitbang_interface = &sysfsgpio_bitbang;

        LOG_INFO("SysfsGPIO JTAG bitbang driver");

        if (!(is_gpio_valid(tck_gpio)
                        && is_gpio_valid(tms_gpio)
                        && is_gpio_valid(tdi_gpio)
                        && is_gpio_valid(tdo_gpio))) {
                if (!is_gpio_valid(tck_gpio))
                        LOG_ERROR("gpio num for tck is invalid");
                if (!is_gpio_valid(tms_gpio))
                        LOG_ERROR("gpio num for tms is invalid");
                if (!is_gpio_valid(tdo_gpio))
                        LOG_ERROR("gpio num for tdo is invalid");
                if (!is_gpio_valid(tdi_gpio))
                        LOG_ERROR("gpio num for tdi is invalid");

                LOG_ERROR("Require tck, tms, tdi and tdo gpios to all be specified");
                return ERROR_JTAG_INIT_FAILED;
        }

        if (!is_gpio_valid(trst_gpio) && !is_gpio_valid(srst_gpio)) {
                LOG_ERROR("Require at least one of trst or srst gpios to be specified");
                return ERROR_JTAG_INIT_FAILED;
        }

        /*
         * Configure TDO as an input, and TDI, TCK, TMS, TRST, SRST
         * as outputs.  Drive TDI and TCK low, and TMS/TRST/SRST high.
         */
        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*/
        trst_fd = setup_sysfs_gpio(trst_gpio, 1, 1);
        if (trst_gpio > 0 && trst_fd < 0)
                goto out_error;

        /* assume active low*/
        srst_fd = setup_sysfs_gpio(srst_gpio, 1, 1);
        if (srst_gpio > 0 && 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;
}