jtag: only change state if necessary

[openocd.git] / src / jtag / drivers / arm-jtag-ew.c

/***************************************************************************
 *   Copyright (C) 2009 by Dimitar Dimitrov <dinuxbg@gmail.com>            *
 *   based on Dominic Rath's and Benedikt Sauter's usbprog.c               *
 *                                                                         *
 *   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.             *
 ***************************************************************************/

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <jtag/interface.h>
#include <jtag/commands.h>
#include <usb.h>
#include "usb_common.h"

#define USB_VID                                         0x15ba
#define USB_PID                                         0x001e

#define ARMJTAGEW_EPT_BULK_OUT          0x01u
#define ARMJTAGEW_EPT_BULK_IN           0x82u

#define ARMJTAGEW_USB_TIMEOUT           2000

#define ARMJTAGEW_IN_BUFFER_SIZE        (4*1024)
#define ARMJTAGEW_OUT_BUFFER_SIZE       (4*1024)

/* USB command request codes. */
#define CMD_GET_VERSION                         0x00
#define CMD_SELECT_DPIMPL                       0x10
#define CMD_SET_TCK_FREQUENCY           0x11
#define CMD_GET_TCK_FREQUENCY           0x12
#define CMD_MEASURE_MAX_TCK_FREQ        0x15
#define CMD_MEASURE_RTCK_RESPONSE       0x16
#define CMD_TAP_SHIFT                           0x17
#define CMD_SET_TAPHW_STATE                     0x20
#define CMD_GET_TAPHW_STATE                     0x21
#define CMD_TGPWR_SETUP                         0x22

/* Global USB buffers */
static uint8_t usb_in_buffer[ARMJTAGEW_IN_BUFFER_SIZE];
static uint8_t usb_out_buffer[ARMJTAGEW_OUT_BUFFER_SIZE];

/* Queue command functions */
static void armjtagew_end_state(tap_state_t state);
static void armjtagew_state_move(void);
static void armjtagew_path_move(int num_states, tap_state_t *path);
static void armjtagew_runtest(int num_cycles);
static void armjtagew_scan(bool ir_scan,
                enum scan_type type,
                uint8_t *buffer,
                int scan_size,
                struct scan_command *command);
static void armjtagew_reset(int trst, int srst);
/* static void armjtagew_simple_command(uint8_t command); */
static int armjtagew_get_status(void);

/* tap buffer functions */
static void armjtagew_tap_init(void);
static int armjtagew_tap_execute(void);
static void armjtagew_tap_ensure_space(int scans, int bits);
static void armjtagew_tap_append_step(int tms, int tdi);
static void armjtagew_tap_append_scan(int length, uint8_t *buffer, struct scan_command *command);

/* ARM-JTAG-EW lowlevel functions */
struct armjtagew {
        struct usb_dev_handle *usb_handle;
};

static struct armjtagew *armjtagew_usb_open(void);
static void armjtagew_usb_close(struct armjtagew *armjtagew);
static int armjtagew_usb_message(struct armjtagew *armjtagew, int out_length, int in_length);
static int armjtagew_usb_write(struct armjtagew *armjtagew, int out_length);
static int armjtagew_usb_read(struct armjtagew *armjtagew, int exp_in_length);

/* helper functions */
static int armjtagew_get_version_info(void);

#ifdef _DEBUG_USB_COMMS_
static void armjtagew_debug_buffer(uint8_t *buffer, int length);
#endif

static struct armjtagew *armjtagew_handle;

/**************************************************************************
 * External interface implementation */

static int armjtagew_execute_queue(void)
{
        struct jtag_command *cmd = jtag_command_queue;
        int scan_size;
        enum scan_type type;
        uint8_t *buffer;

        while (cmd != NULL) {
                switch (cmd->type) {
                        case JTAG_RUNTEST:
                                DEBUG_JTAG_IO("runtest %i cycles, end in %i",
                                                cmd->cmd.runtest->num_cycles, \
                                                cmd->cmd.runtest->end_state);

                                armjtagew_end_state(cmd->cmd.runtest->end_state);
                                armjtagew_runtest(cmd->cmd.runtest->num_cycles);
                                break;

                        case JTAG_TLR_RESET:
                                DEBUG_JTAG_IO("statemove end in %i", cmd->cmd.statemove->end_state);

                                armjtagew_end_state(cmd->cmd.statemove->end_state);
                                armjtagew_state_move();
                                break;

                        case JTAG_PATHMOVE:
                                DEBUG_JTAG_IO("pathmove: %i states, end in %i", \
                                                cmd->cmd.pathmove->num_states, \
                                                cmd->cmd.pathmove->path[cmd->cmd.pathmove->num_states - 1]);

                                armjtagew_path_move(cmd->cmd.pathmove->num_states,
                                                cmd->cmd.pathmove->path);
                                break;

                        case JTAG_SCAN:
                                DEBUG_JTAG_IO("scan end in %i", cmd->cmd.scan->end_state);

                                armjtagew_end_state(cmd->cmd.scan->end_state);

                                scan_size = jtag_build_buffer(cmd->cmd.scan, &buffer);
                                DEBUG_JTAG_IO("scan input, length = %d", scan_size);

#ifdef _DEBUG_USB_COMMS_
                                armjtagew_debug_buffer(buffer, (scan_size + 7) / 8);
#endif
                                type = jtag_scan_type(cmd->cmd.scan);
                                armjtagew_scan(cmd->cmd.scan->ir_scan,
                                                type, buffer,
                                                scan_size, cmd->cmd.scan);
                                break;

                        case JTAG_RESET:
                                DEBUG_JTAG_IO("reset trst: %i srst %i",
                                                cmd->cmd.reset->trst,
                                                cmd->cmd.reset->srst);

                                armjtagew_tap_execute();

                                if (cmd->cmd.reset->trst == 1)
                                        tap_set_state(TAP_RESET);
                                armjtagew_reset(cmd->cmd.reset->trst, cmd->cmd.reset->srst);
                                break;

                        case JTAG_SLEEP:
                                DEBUG_JTAG_IO("sleep %i", cmd->cmd.sleep->us);
                                armjtagew_tap_execute();
                                jtag_sleep(cmd->cmd.sleep->us);
                                break;

                        default:
                                LOG_ERROR("BUG: unknown JTAG command type encountered");
                                exit(-1);
                }
                cmd = cmd->next;
        }

        return armjtagew_tap_execute();
}

/* Sets speed in kHz. */
static int armjtagew_speed(int speed)
{
        int result;
        int speed_real;


        usb_out_buffer[0] = CMD_SET_TCK_FREQUENCY;
        buf_set_u32(usb_out_buffer + 1, 0, 32, speed*1000);

        result = armjtagew_usb_message(armjtagew_handle, 5, 4);

        if (result < 0) {
                LOG_ERROR("ARM-JTAG-EW setting speed failed (%d)", result);
                return ERROR_JTAG_DEVICE_ERROR;
        }

        usb_out_buffer[0] = CMD_GET_TCK_FREQUENCY;
        result = armjtagew_usb_message(armjtagew_handle, 1, 4);
        speed_real = (int)buf_get_u32(usb_in_buffer, 0, 32) / 1000;
        if (result < 0) {
                LOG_ERROR("ARM-JTAG-EW getting speed failed (%d)", result);
                return ERROR_JTAG_DEVICE_ERROR;
        } else
                LOG_INFO("Requested speed %dkHz, emulator reported %dkHz.", speed, speed_real);

        return ERROR_OK;
}

static int armjtagew_khz(int khz, int *jtag_speed)
{
        *jtag_speed = khz;

        return ERROR_OK;
}

static int armjtagew_speed_div(int speed, int *khz)
{
        *khz = speed;

        return ERROR_OK;
}

static int armjtagew_init(void)
{
        int check_cnt;

        armjtagew_handle = armjtagew_usb_open();

        if (armjtagew_handle == 0) {
                LOG_ERROR(
                        "Cannot find ARM-JTAG-EW Interface! Please check connection and permissions.");
                return ERROR_JTAG_INIT_FAILED;
        }

        check_cnt = 0;
        while (check_cnt < 3) {
                if (armjtagew_get_version_info() == ERROR_OK) {
                        /* attempt to get status */
                        armjtagew_get_status();
                        break;
                }

                check_cnt++;
        }

        if (check_cnt == 3)
                LOG_INFO("ARM-JTAG-EW initial read failed, don't worry");

        /* Initial JTAG speed (for reset and initialization): 32 kHz */
        armjtagew_speed(32);

        LOG_INFO("ARM-JTAG-EW JTAG Interface ready");

        armjtagew_reset(0, 0);
        armjtagew_tap_init();

        return ERROR_OK;
}

static int armjtagew_quit(void)
{
        armjtagew_usb_close(armjtagew_handle);
        return ERROR_OK;
}

/**************************************************************************
 * Queue command implementations */

static void armjtagew_end_state(tap_state_t 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);
        }
}

/* Goes to the end state. */
static void armjtagew_state_move(void)
{
        int i;
        int tms = 0;
        uint8_t tms_scan = tap_get_tms_path(tap_get_state(), tap_get_end_state());
        int tms_count = tap_get_tms_path_len(tap_get_state(), tap_get_end_state());

        for (i = 0; i < tms_count; i++) {
                tms = (tms_scan >> i) & 1;
                armjtagew_tap_append_step(tms, 0);
        }

        tap_set_state(tap_get_end_state());
}

static void armjtagew_path_move(int num_states, tap_state_t *path)
{
        int i;

        for (i = 0; i < num_states; i++) {
                /*
                 * TODO: The ARM-JTAG-EW hardware delays TDI with 3 TCK cycles when in RTCK mode.
                 * Either handle that here, or update the documentation with examples
                 * how to fix that in the configuration files.
                 */
                if (path[i] == tap_state_transition(tap_get_state(), false))
                        armjtagew_tap_append_step(0, 0);
                else if (path[i] == tap_state_transition(tap_get_state(), true))
                        armjtagew_tap_append_step(1, 0);
                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]);
        }

        tap_set_end_state(tap_get_state());
}

static void armjtagew_runtest(int num_cycles)
{
        int i;

        tap_state_t 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) {
                armjtagew_end_state(TAP_IDLE);
                armjtagew_state_move();
        }

        /* execute num_cycles */
        for (i = 0; i < num_cycles; i++)
                armjtagew_tap_append_step(0, 0);

        /* finish in end_state */
        armjtagew_end_state(saved_end_state);
        if (tap_get_state() != tap_get_end_state())
                armjtagew_state_move();
}

static void armjtagew_scan(bool ir_scan,
        enum scan_type type,
        uint8_t *buffer,
        int scan_size,
        struct scan_command *command)
{
        tap_state_t saved_end_state;

        armjtagew_tap_ensure_space(1, scan_size + 8);

        saved_end_state = tap_get_end_state();

        /* Move to appropriate scan state */
        armjtagew_end_state(ir_scan ? TAP_IRSHIFT : TAP_DRSHIFT);

        /* Only move if we're not already there */
        if (tap_get_state() != tap_get_end_state())
                armjtagew_state_move();

        armjtagew_end_state(saved_end_state);

        /* Scan */
        armjtagew_tap_append_scan(scan_size, buffer, command);

        /* We are in Exit1, go to Pause */
        armjtagew_tap_append_step(0, 0);

        tap_set_state(ir_scan ? TAP_IRPAUSE : TAP_DRPAUSE);

        if (tap_get_state() != tap_get_end_state())
                armjtagew_state_move();
}

static void armjtagew_reset(int trst, int srst)
{
        const uint8_t trst_mask = (1u << 5);
        const uint8_t srst_mask = (1u << 6);
        uint8_t val = 0;
        uint8_t outp_en = 0;
        uint8_t change_mask = 0;
        int result;

        LOG_DEBUG("trst: %i, srst: %i", trst, srst);

        if (srst == 0) {
                val |= srst_mask;
                outp_en &= ~srst_mask;          /* tristate */
                change_mask |= srst_mask;
        } else if (srst == 1) {
                val &= ~srst_mask;
                outp_en |= srst_mask;
                change_mask |= srst_mask;
        }

        if (trst == 0) {
                val |= trst_mask;
                outp_en &= ~trst_mask;          /* tristate */
                change_mask |= trst_mask;
        } else if (trst == 1) {
                val &= ~trst_mask;
                outp_en |= trst_mask;
                change_mask |= trst_mask;
        }

        usb_out_buffer[0] = CMD_SET_TAPHW_STATE;
        usb_out_buffer[1] = val;
        usb_out_buffer[2] = outp_en;
        usb_out_buffer[3] = change_mask;
        result = armjtagew_usb_write(armjtagew_handle, 4);
        if (result != 4)
                LOG_ERROR("ARM-JTAG-EW TRST/SRST pin set failed failed (%d)", result);
}

static int armjtagew_get_status(void)
{
        int result;

        usb_out_buffer[0] = CMD_GET_TAPHW_STATE;
        result = armjtagew_usb_message(armjtagew_handle, 1, 12);

        if (result == 0) {
                unsigned int u_tg = buf_get_u32(usb_in_buffer, 0, 16);
                LOG_INFO(
                        "U_tg = %d mV, U_aux = %d mV, U_tgpwr = %d mV, I_tgpwr = %d mA, D1 = %d, Target power %s %s",
                        (int)(buf_get_u32(usb_in_buffer + 0, 0, 16)),
                        (int)(buf_get_u32(usb_in_buffer + 2, 0, 16)),
                        (int)(buf_get_u32(usb_in_buffer + 4, 0, 16)),
                        (int)(buf_get_u32(usb_in_buffer + 6, 0, 16)),
                        usb_in_buffer[9],
                        usb_in_buffer[11] ? "OVERCURRENT" : "OK",
                        usb_in_buffer[10] ? "enabled" : "disabled");

                if (u_tg < 1500)
                        LOG_ERROR("Vref too low. Check Target Power");
        } else
                LOG_ERROR("ARM-JTAG-EW command CMD_GET_TAPHW_STATE failed (%d)", result);

        return ERROR_OK;
}

static int armjtagew_get_version_info(void)
{
        int result;
        char sn[16];
        char auxinfo[257];

        /* query hardware version */
        usb_out_buffer[0] = CMD_GET_VERSION;
        result = armjtagew_usb_message(armjtagew_handle, 1, 4 + 15 + 256);

        if (result != 0) {
                LOG_ERROR("ARM-JTAG-EW command CMD_GET_VERSION failed (%d)", result);
                return ERROR_JTAG_DEVICE_ERROR;
        }

        memcpy(sn, usb_in_buffer + 4, 15);
        sn[15] = '\0';
        memcpy(auxinfo, usb_in_buffer + 4+15, 256);
        auxinfo[256] = '\0';

        LOG_INFO(
                "ARM-JTAG-EW firmware version %d.%d, hardware revision %c, SN=%s, Additional info: %s", \
                usb_in_buffer[1],
                usb_in_buffer[0], \
                isgraph(usb_in_buffer[2]) ? usb_in_buffer[2] : 'X', \
                sn,
                auxinfo);

        if (1 != usb_in_buffer[1] || 6 != usb_in_buffer[0])
                LOG_WARNING(
                        "ARM-JTAG-EW firmware version %d.%d is untested with this version of OpenOCD. You might experience unexpected behavior.",
                        usb_in_buffer[1],
                        usb_in_buffer[0]);
        return ERROR_OK;
}

COMMAND_HANDLER(armjtagew_handle_armjtagew_info_command)
{
        if (armjtagew_get_version_info() == ERROR_OK) {
                /* attempt to get status */
                armjtagew_get_status();
        }

        return ERROR_OK;
}

static const struct command_registration armjtagew_command_handlers[] = {
        {
                .name = "armjtagew_info",
                .handler = &armjtagew_handle_armjtagew_info_command,
                .mode = COMMAND_EXEC,
                .help = "query armjtagew info",
        },
        COMMAND_REGISTRATION_DONE
};

struct jtag_interface armjtagew_interface = {
        .name = "arm-jtag-ew",
        .commands = armjtagew_command_handlers,
        .transports = jtag_only,
        .execute_queue = armjtagew_execute_queue,
        .speed = armjtagew_speed,
        .speed_div = armjtagew_speed_div,
        .khz = armjtagew_khz,
        .init = armjtagew_init,
        .quit = armjtagew_quit,
};

/**************************************************************************
 * ARM-JTAG-EW tap functions */

/* 2048 is the max value we can use here */
#define ARMJTAGEW_TAP_BUFFER_SIZE 2048

static int tap_length;
static uint8_t tms_buffer[ARMJTAGEW_TAP_BUFFER_SIZE];
static uint8_t tdi_buffer[ARMJTAGEW_TAP_BUFFER_SIZE];
static uint8_t tdo_buffer[ARMJTAGEW_TAP_BUFFER_SIZE];

struct pending_scan_result {
        int first;      /* First bit position in tdo_buffer to read */
        int length;     /* Number of bits to read */
        struct scan_command *command;   /* Corresponding scan command */
        uint8_t *buffer;
};

#define MAX_PENDING_SCAN_RESULTS 256

static int pending_scan_results_length;
static struct pending_scan_result pending_scan_results_buffer[MAX_PENDING_SCAN_RESULTS];

static int last_tms;

static void armjtagew_tap_init(void)
{
        tap_length = 0;
        pending_scan_results_length = 0;
}

static void armjtagew_tap_ensure_space(int scans, int bits)
{
        int available_scans = MAX_PENDING_SCAN_RESULTS - pending_scan_results_length;
        int available_bits = ARMJTAGEW_TAP_BUFFER_SIZE * 8 - tap_length;

        if (scans > available_scans || bits > available_bits)
                armjtagew_tap_execute();
}

static void armjtagew_tap_append_step(int tms, int tdi)
{
        last_tms = tms;
        int index_local = tap_length / 8;

        if (index_local < ARMJTAGEW_TAP_BUFFER_SIZE) {
                int bit_index = tap_length % 8;
                uint8_t bit = 1 << bit_index;

                if (tms)
                        tms_buffer[index_local] |= bit;
                else
                        tms_buffer[index_local] &= ~bit;

                if (tdi)
                        tdi_buffer[index_local] |= bit;
                else
                        tdi_buffer[index_local] &= ~bit;

                tap_length++;
        } else
                LOG_ERROR("armjtagew_tap_append_step, overflow");
}

void armjtagew_tap_append_scan(int length, uint8_t *buffer, struct scan_command *command)
{
        struct pending_scan_result *pending_scan_result =
                &pending_scan_results_buffer[pending_scan_results_length];
        int i;

        pending_scan_result->first = tap_length;
        pending_scan_result->length = length;
        pending_scan_result->command = command;
        pending_scan_result->buffer = buffer;

        for (i = 0; i < length; i++)
                armjtagew_tap_append_step((i < length-1 ? 0 : 1), (buffer[i/8] >> (i%8)) & 1);
        pending_scan_results_length++;
}

/* Pad and send a tap sequence to the device, and receive the answer.
 * For the purpose of padding we assume that we are in idle or pause state. */
static int armjtagew_tap_execute(void)
{
        int byte_length;
        int tms_offset;
        int tdi_offset;
        int i;
        int result;

        if (tap_length > 0) {
                /* Pad last byte so that tap_length is divisible by 8 */
                while (tap_length % 8 != 0) {
                        /* More of the last TMS value keeps us in the same state,
                         * analogous to free-running JTAG interfaces. */
                        armjtagew_tap_append_step(last_tms, 0);
                }

                byte_length = tap_length / 8;

                usb_out_buffer[0] = CMD_TAP_SHIFT;
                buf_set_u32(usb_out_buffer + 1, 0, 16, byte_length);

                tms_offset = 3;
                for (i = 0; i < byte_length; i++)
                        usb_out_buffer[tms_offset + i] = flip_u32(tms_buffer[i], 8);

                tdi_offset = tms_offset + byte_length;
                for (i = 0; i < byte_length; i++)
                        usb_out_buffer[tdi_offset + i] = flip_u32(tdi_buffer[i], 8);

                result = armjtagew_usb_message(armjtagew_handle,
                                3 + 2 * byte_length,
                                byte_length + 4);

                if (result == 0) {
                        int stat_local;

                        stat_local = (int)buf_get_u32(usb_in_buffer + byte_length, 0, 32);
                        if (stat_local) {
                                LOG_ERROR(
                                        "armjtagew_tap_execute, emulator returned error code %d for a CMD_TAP_SHIFT command",
                                        stat_local);
                                return ERROR_JTAG_QUEUE_FAILED;
                        }

                        for (i = 0; i < byte_length; i++)
                                tdo_buffer[i] = flip_u32(usb_in_buffer[i], 8);

                        for (i = 0; i < pending_scan_results_length; i++) {
                                struct pending_scan_result *pending_scan_result =
                                        &pending_scan_results_buffer[i];
                                uint8_t *buffer = pending_scan_result->buffer;
                                int length = pending_scan_result->length;
                                int first = pending_scan_result->first;
                                struct scan_command *command = pending_scan_result->command;

                                /* Copy to buffer */
                                buf_set_buf(tdo_buffer, first, buffer, 0, length);

                                DEBUG_JTAG_IO("pending scan result, length = %d", length);

#ifdef _DEBUG_USB_COMMS_
                                armjtagew_debug_buffer(buffer, byte_length);
#endif

                                if (jtag_read_buffer(buffer, command) != ERROR_OK) {
                                        armjtagew_tap_init();
                                        return ERROR_JTAG_QUEUE_FAILED;
                                }

                                if (pending_scan_result->buffer != NULL)
                                        free(pending_scan_result->buffer);
                        }
                } else {
                        LOG_ERROR("armjtagew_tap_execute, wrong result %d, expected %d",
                                result,
                                byte_length);
                        return ERROR_JTAG_QUEUE_FAILED;
                }

                armjtagew_tap_init();
        }

        return ERROR_OK;
}

/****************************************************************************
 * JLink USB low-level functions */

static struct armjtagew *armjtagew_usb_open()
{
        usb_init();

        const uint16_t vids[] = { USB_VID, 0 };
        const uint16_t pids[] = { USB_PID, 0 };
        struct usb_dev_handle *dev;
        if (jtag_usb_open(vids, pids, &dev) != ERROR_OK)
                return NULL;

        struct armjtagew *result = malloc(sizeof(struct armjtagew));
        result->usb_handle = dev;

#if 0
        /* usb_set_configuration required under win32 */
        usb_set_configuration(dev, dev->config[0].bConfigurationValue);
#endif
        usb_claim_interface(dev, 0);
#if 0
        /*
         * This makes problems under Mac OS X. And is not needed
         * under Windows. Hopefully this will not break a linux build
         */
        usb_set_altinterface(dev, 0);
#endif
        return result;
}

static void armjtagew_usb_close(struct armjtagew *armjtagew)
{
        usb_close(armjtagew->usb_handle);
        free(armjtagew);
}

/* Send a message and receive the reply. */
static int armjtagew_usb_message(struct armjtagew *armjtagew, int out_length, int in_length)
{
        int result;

        result = armjtagew_usb_write(armjtagew, out_length);
        if (result == out_length) {
                result = armjtagew_usb_read(armjtagew, in_length);
                if (result != in_length) {
                        LOG_ERROR("usb_bulk_read failed (requested=%d, result=%d)",
                                in_length,
                                result);
                        return -1;
                }
        } else {
                LOG_ERROR("usb_bulk_write failed (requested=%d, result=%d)", out_length, result);
                return -1;
        }
        return 0;
}

/* Write data from out_buffer to USB. */
static int armjtagew_usb_write(struct armjtagew *armjtagew, int out_length)
{
        int result;

        if (out_length > ARMJTAGEW_OUT_BUFFER_SIZE) {
                LOG_ERROR("armjtagew_write illegal out_length=%d (max=%d)",
                        out_length,
                        ARMJTAGEW_OUT_BUFFER_SIZE);
                return -1;
        }

        result = usb_bulk_write(armjtagew->usb_handle, ARMJTAGEW_EPT_BULK_OUT, \
                        (char *)usb_out_buffer, out_length, ARMJTAGEW_USB_TIMEOUT);

        DEBUG_JTAG_IO("armjtagew_usb_write, out_length = %d, result = %d", out_length, result);

#ifdef _DEBUG_USB_COMMS_
        armjtagew_debug_buffer(usb_out_buffer, out_length);
#endif
        return result;
}

/* Read data from USB into in_buffer. */
static int armjtagew_usb_read(struct armjtagew *armjtagew, int exp_in_length)
{
        int result = usb_bulk_read(armjtagew->usb_handle, ARMJTAGEW_EPT_BULK_IN, \
                        (char *)usb_in_buffer, exp_in_length, ARMJTAGEW_USB_TIMEOUT);

        DEBUG_JTAG_IO("armjtagew_usb_read, result = %d", result);

#ifdef _DEBUG_USB_COMMS_
        armjtagew_debug_buffer(usb_in_buffer, result);
#endif
        return result;
}

#ifdef _DEBUG_USB_COMMS_
#define BYTES_PER_LINE  16

static void armjtagew_debug_buffer(uint8_t *buffer, int length)
{
        char line[81];
        char s[4];
        int i;
        int j;

        for (i = 0; i < length; i += BYTES_PER_LINE) {
                snprintf(line, 5, "%04x", i);
                for (j = i; j < i + BYTES_PER_LINE && j < length; j++) {
                        snprintf(s, 4, " %02x", buffer[j]);
                        strcat(line, s);
                }
                LOG_DEBUG("%s", line);

                /* Prevent GDB timeout (writing to log might take some time) */
                keep_alive();
        }
}
#endif