linuxgpiod.c

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// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Bitbang driver for Linux GPIO descriptors through libgpiod
 * Copyright (C) 2020 Antonio Borneo <borneo.antonio@gmail.com>
 *
 * Largely based on sysfsgpio driver
 * Copyright (C) 2012 by Creative Product Design, marc @ cpdesign.com.au
 * Copyright (C) 2014 by Jean-Christian de Rivaz <jc@eclis.ch>
 * Copyright (C) 2014 by Paul Fertser <fercerpav@gmail.com>
 */
 
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
 
#include <gpiod.h>
#include <jtag/adapter.h>
#include <jtag/interface.h>
#include <transport/transport.h>
#include "bitbang.h"
 
static struct gpiod_chip *gpiod_chip[ADAPTER_GPIO_IDX_NUM] = {};
static struct gpiod_line *gpiod_line[ADAPTER_GPIO_IDX_NUM] = {};
 
static int last_swclk;
static int last_swdio;
static bool last_stored;
static bool swdio_input;
 
static const struct adapter_gpio_config *adapter_gpio_config;
 
/*
 * Helper function to determine if gpio config is valid
 *
 * Assume here that there will be less than 10000 gpios per gpiochip, and less
 * than 1000 gpiochips.
 */
static bool is_gpio_config_valid(enum adapter_gpio_config_index idx)
{
    return adapter_gpio_config[idx].chip_num >= 0
        && adapter_gpio_config[idx].chip_num < 1000
        && adapter_gpio_config[idx].gpio_num >= 0
        && adapter_gpio_config[idx].gpio_num < 10000;
}
 
/* Bitbang interface read of TDO */
static bb_value_t linuxgpiod_read(void)
{
    int retval;
 
    retval = gpiod_line_get_value(gpiod_line[ADAPTER_GPIO_IDX_TDO]);
    if (retval < 0) {
        LOG_WARNING("reading tdo failed");
        return 0;
    }
 
    return retval ? BB_HIGH : BB_LOW;
}
 
/*
 * 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 linuxgpiod_write(int tck, int tms, int tdi)
{
    static int last_tck;
    static int last_tms;
    static int last_tdi;
 
    static int first_time;
 
    int retval;
 
    if (!first_time) {
        last_tck = !tck;
        last_tms = !tms;
        last_tdi = !tdi;
        first_time = 1;
    }
 
    if (tdi != last_tdi) {
        retval = gpiod_line_set_value(gpiod_line[ADAPTER_GPIO_IDX_TDI], tdi);
        if (retval < 0)
            LOG_WARNING("writing tdi failed");
    }
 
    if (tms != last_tms) {
        retval = gpiod_line_set_value(gpiod_line[ADAPTER_GPIO_IDX_TMS], tms);
        if (retval < 0)
            LOG_WARNING("writing tms failed");
    }
 
    /* write clk last */
    if (tck != last_tck) {
        retval = gpiod_line_set_value(gpiod_line[ADAPTER_GPIO_IDX_TCK], tck);
        if (retval < 0)
            LOG_WARNING("writing tck failed");
    }
 
    last_tdi = tdi;
    last_tms = tms;
    last_tck = tck;
 
    return ERROR_OK;
}
 
static int linuxgpiod_swdio_read(void)
{
    int retval;
 
    retval = gpiod_line_get_value(gpiod_line[ADAPTER_GPIO_IDX_SWDIO]);
    if (retval < 0) {
        LOG_WARNING("Fail read swdio");
        return 0;
    }
 
    return retval;
}
 
static void linuxgpiod_swdio_drive(bool is_output)
{
    int retval;
 
    /*
     * FIXME: change direction requires release and re-require the line
     * https://stackoverflow.com/questions/58735140/
     * this would change in future libgpiod
     */
    gpiod_line_release(gpiod_line[ADAPTER_GPIO_IDX_SWDIO]);
 
    if (is_output) {
        if (gpiod_line[ADAPTER_GPIO_IDX_SWDIO_DIR]) {
            retval = gpiod_line_set_value(gpiod_line[ADAPTER_GPIO_IDX_SWDIO_DIR], 1);
            if (retval < 0)
                LOG_WARNING("Fail set swdio_dir");
        }
        retval = gpiod_line_request_output(gpiod_line[ADAPTER_GPIO_IDX_SWDIO], "OpenOCD", 1);
        if (retval < 0)
            LOG_WARNING("Fail request_output line swdio");
    } else {
        retval = gpiod_line_request_input(gpiod_line[ADAPTER_GPIO_IDX_SWDIO], "OpenOCD");
        if (retval < 0)
            LOG_WARNING("Fail request_input line swdio");
        if (gpiod_line[ADAPTER_GPIO_IDX_SWDIO_DIR]) {
            retval = gpiod_line_set_value(gpiod_line[ADAPTER_GPIO_IDX_SWDIO_DIR], 0);
            if (retval < 0)
                LOG_WARNING("Fail set swdio_dir");
        }
    }
 
    last_stored = false;
    swdio_input = !is_output;
}
 
static int linuxgpiod_swd_write(int swclk, int swdio)
{
    int retval;
 
    if (!swdio_input) {
        if (!last_stored || (swdio != last_swdio)) {
            retval = gpiod_line_set_value(gpiod_line[ADAPTER_GPIO_IDX_SWDIO], swdio);
            if (retval < 0)
                LOG_WARNING("Fail set swdio");
        }
    }
 
    /* write swclk last */
    if (!last_stored || (swclk != last_swclk)) {
        retval = gpiod_line_set_value(gpiod_line[ADAPTER_GPIO_IDX_SWCLK], swclk);
        if (retval < 0)
            LOG_WARNING("Fail set swclk");
    }
 
    last_swdio = swdio;
    last_swclk = swclk;
    last_stored = true;
 
    return ERROR_OK;
}
 
static int linuxgpiod_blink(int on)
{
    int retval;
 
    if (!is_gpio_config_valid(ADAPTER_GPIO_IDX_LED))
        return ERROR_OK;
 
    retval = gpiod_line_set_value(gpiod_line[ADAPTER_GPIO_IDX_LED], on);
    if (retval < 0)
        LOG_WARNING("Fail set led");
    return retval;
}
 
static struct bitbang_interface linuxgpiod_bitbang = {
    .read = linuxgpiod_read,
    .write = linuxgpiod_write,
    .swdio_read = linuxgpiod_swdio_read,
    .swdio_drive = linuxgpiod_swdio_drive,
    .swd_write = linuxgpiod_swd_write,
    .blink = linuxgpiod_blink,
};
 
/*
 * Bitbang interface to manipulate reset lines SRST and TRST
 *
 * (1) assert or (0) deassert reset lines
 */
static int linuxgpiod_reset(int trst, int srst)
{
    int retval1 = 0, retval2 = 0;
 
    LOG_DEBUG("linuxgpiod_reset");
 
    /*
     * active low behaviour handled by "adaptor gpio" command and
     * GPIOD_LINE_REQUEST_FLAG_ACTIVE_LOW flag when requesting the line.
     */
    if (gpiod_line[ADAPTER_GPIO_IDX_SRST]) {
        retval1 = gpiod_line_set_value(gpiod_line[ADAPTER_GPIO_IDX_SRST], srst);
        if (retval1 < 0)
            LOG_WARNING("set srst value failed");
    }
 
    if (gpiod_line[ADAPTER_GPIO_IDX_TRST]) {
        retval2 = gpiod_line_set_value(gpiod_line[ADAPTER_GPIO_IDX_TRST], trst);
        if (retval2 < 0)
            LOG_WARNING("set trst value failed");
    }
 
    return ((retval1 < 0) || (retval2 < 0)) ? ERROR_FAIL : ERROR_OK;
}
 
static bool linuxgpiod_jtag_mode_possible(void)
{
    if (!is_gpio_config_valid(ADAPTER_GPIO_IDX_TCK))
        return false;
    if (!is_gpio_config_valid(ADAPTER_GPIO_IDX_TMS))
        return false;
    if (!is_gpio_config_valid(ADAPTER_GPIO_IDX_TDI))
        return false;
    if (!is_gpio_config_valid(ADAPTER_GPIO_IDX_TDO))
        return false;
    return true;
}
 
static bool linuxgpiod_swd_mode_possible(void)
{
    if (!is_gpio_config_valid(ADAPTER_GPIO_IDX_SWCLK))
        return false;
    if (!is_gpio_config_valid(ADAPTER_GPIO_IDX_SWDIO))
        return false;
    return true;
}
 
static inline void helper_release(enum adapter_gpio_config_index idx)
{
    if (gpiod_line[idx]) {
        gpiod_line_release(gpiod_line[idx]);
        gpiod_line[idx] = NULL;
    }
    if (gpiod_chip[idx]) {
        gpiod_chip_close(gpiod_chip[idx]);
        gpiod_chip[idx] = NULL;
    }
}
 
static int linuxgpiod_quit(void)
{
    LOG_DEBUG("linuxgpiod_quit");
    for (int i = 0; i < ADAPTER_GPIO_IDX_NUM; ++i)
        helper_release(i);
 
    return ERROR_OK;
}
 
static int helper_get_line(enum adapter_gpio_config_index idx)
{
    if (!is_gpio_config_valid(idx))
        return ERROR_OK;
 
    int dir = GPIOD_LINE_REQUEST_DIRECTION_INPUT, flags = 0, val = 0, retval;
 
    gpiod_chip[idx] = gpiod_chip_open_by_number(adapter_gpio_config[idx].chip_num);
    if (!gpiod_chip[idx]) {
        LOG_ERROR("Cannot open LinuxGPIOD chip %d for %s", adapter_gpio_config[idx].chip_num,
            adapter_gpio_get_name(idx));
        return ERROR_JTAG_INIT_FAILED;
    }
 
    gpiod_line[idx] = gpiod_chip_get_line(gpiod_chip[idx], adapter_gpio_config[idx].gpio_num);
    if (!gpiod_line[idx]) {
        LOG_ERROR("Error get line %s", adapter_gpio_get_name(idx));
        return ERROR_JTAG_INIT_FAILED;
    }
 
    switch (adapter_gpio_config[idx].init_state) {
    case ADAPTER_GPIO_INIT_STATE_INPUT:
        dir = GPIOD_LINE_REQUEST_DIRECTION_INPUT;
        break;
    case ADAPTER_GPIO_INIT_STATE_INACTIVE:
        dir = GPIOD_LINE_REQUEST_DIRECTION_OUTPUT;
        val = 0;
        break;
    case ADAPTER_GPIO_INIT_STATE_ACTIVE:
        dir = GPIOD_LINE_REQUEST_DIRECTION_OUTPUT;
        val = 1;
        break;
    }
 
    switch (adapter_gpio_config[idx].drive) {
    case ADAPTER_GPIO_DRIVE_MODE_PUSH_PULL:
        break;
    case ADAPTER_GPIO_DRIVE_MODE_OPEN_DRAIN:
        flags |= GPIOD_LINE_REQUEST_FLAG_OPEN_DRAIN;
        break;
    case ADAPTER_GPIO_DRIVE_MODE_OPEN_SOURCE:
        flags |= GPIOD_LINE_REQUEST_FLAG_OPEN_SOURCE;
        break;
    }
 
    switch (adapter_gpio_config[idx].pull) {
    case ADAPTER_GPIO_PULL_NONE:
#ifdef GPIOD_LINE_REQUEST_FLAG_BIAS_DISABLE
        flags |= GPIOD_LINE_REQUEST_FLAG_BIAS_DISABLE;
#endif
        break;
    case ADAPTER_GPIO_PULL_UP:
#ifdef GPIOD_LINE_REQUEST_FLAG_BIAS_PULL_UP
        flags |= GPIOD_LINE_REQUEST_FLAG_BIAS_PULL_UP;
#else
        LOG_WARNING("linuxgpiod: ignoring request for pull-up on %s: not supported by gpiod v%s",
            adapter_gpio_get_name(idx), gpiod_version_string());
#endif
        break;
    case ADAPTER_GPIO_PULL_DOWN:
#ifdef GPIOD_LINE_REQUEST_FLAG_BIAS_PULL_DOWN
        flags |= GPIOD_LINE_REQUEST_FLAG_BIAS_PULL_DOWN;
#else
        LOG_WARNING("linuxgpiod: ignoring request for pull-down on %s: not supported by gpiod v%s",
            adapter_gpio_get_name(idx), gpiod_version_string());
#endif
        break;
    }
 
    if (adapter_gpio_config[idx].active_low)
        flags |= GPIOD_LINE_REQUEST_FLAG_ACTIVE_LOW;
 
    struct gpiod_line_request_config config = {
        .consumer = "OpenOCD",
        .request_type = dir,
        .flags = flags,
    };
 
    retval = gpiod_line_request(gpiod_line[idx], &config, val);
    if (retval < 0) {
        LOG_ERROR("Error requesting gpio line %s", adapter_gpio_get_name(idx));
        return ERROR_JTAG_INIT_FAILED;
    }
 
    return ERROR_OK;
}
 
static int linuxgpiod_init(void)
{
    LOG_INFO("Linux GPIOD JTAG/SWD bitbang driver");
 
    bitbang_interface = &linuxgpiod_bitbang;
    adapter_gpio_config = adapter_gpio_get_config();
 
    /*
     * Configure JTAG/SWD signals. Default directions and initial states are handled
     * by adapter.c and "adapter gpio" command.
     */
 
    if (transport_is_jtag()) {
        if (!linuxgpiod_jtag_mode_possible()) {
            LOG_ERROR("Require tck, tms, tdi and tdo gpios for JTAG mode");
            goto out_error;
        }
 
        if (helper_get_line(ADAPTER_GPIO_IDX_TDO) != ERROR_OK ||
            helper_get_line(ADAPTER_GPIO_IDX_TDI) != ERROR_OK ||
            helper_get_line(ADAPTER_GPIO_IDX_TCK) != ERROR_OK ||
            helper_get_line(ADAPTER_GPIO_IDX_TMS) != ERROR_OK ||
            helper_get_line(ADAPTER_GPIO_IDX_TRST) != ERROR_OK)
                goto out_error;
    }
 
    if (transport_is_swd()) {
        int retval1, retval2;
        if (!linuxgpiod_swd_mode_possible()) {
            LOG_ERROR("Require swclk and swdio gpio for SWD mode");
            goto out_error;
        }
 
        /*
         * swdio and its buffer should be initialized in the order that prevents
         * two outputs from being connected together. This will occur if the
         * swdio GPIO is configured as an output while the external buffer is
         * configured to send the swdio signal from the target to the GPIO.
         */
        if (adapter_gpio_config[ADAPTER_GPIO_IDX_SWDIO].init_state == ADAPTER_GPIO_INIT_STATE_INPUT) {
            retval1 = helper_get_line(ADAPTER_GPIO_IDX_SWDIO);
            retval2 = helper_get_line(ADAPTER_GPIO_IDX_SWDIO_DIR);
        } else {
            retval1 = helper_get_line(ADAPTER_GPIO_IDX_SWDIO_DIR);
            retval2 = helper_get_line(ADAPTER_GPIO_IDX_SWDIO);
        }
        if (retval1 != ERROR_OK || retval2 != ERROR_OK)
            goto out_error;
 
        if (helper_get_line(ADAPTER_GPIO_IDX_SWCLK) != ERROR_OK)
            goto out_error;
    }
 
    if (helper_get_line(ADAPTER_GPIO_IDX_SRST) != ERROR_OK ||
        helper_get_line(ADAPTER_GPIO_IDX_LED) != ERROR_OK)
            goto out_error;
 
    return ERROR_OK;
 
out_error:
    linuxgpiod_quit();
 
    return ERROR_JTAG_INIT_FAILED;
}
 
static const char *const linuxgpiod_transport[] = { "swd", "jtag", NULL };
 
static struct jtag_interface linuxgpiod_interface = {
    .supported = DEBUG_CAP_TMS_SEQ,
    .execute_queue = bitbang_execute_queue,
};
 
struct adapter_driver linuxgpiod_adapter_driver = {
    .name = "linuxgpiod",
    .transports = linuxgpiod_transport,
 
    .init = linuxgpiod_init,
    .quit = linuxgpiod_quit,
    .reset = linuxgpiod_reset,
 
    .jtag_ops = &linuxgpiod_interface,
    .swd_ops = &bitbang_swd,
};