adi_v5_swd: Read RDBUFF once after a sequence of AP reads

[openocd.git] / src / target / adi_v5_swd.c

/***************************************************************************
 *
 *   Copyright (C) 2010 by David Brownell
 *
 *   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.,
 *   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 ***************************************************************************/

/**
 * @file
 * Utilities to support ARM "Serial Wire Debug" (SWD), a low pin-count debug
 * link protocol used in cases where JTAG is not wanted.  This is coupled to
 * recent versions of ARM's "CoreSight" debug framework.  This specific code
 * is a transport level interface, with "target/arm_adi_v5.[hc]" code
 * understanding operation semantics, shared with the JTAG transport.
 *
 * Single-DAP support only.
 *
 * for details, see "ARM IHI 0031A"
 * ARM Debug Interface v5 Architecture Specification
 * especially section 5.3 for SWD protocol
 *
 * On many chips (most current Cortex-M3 parts) SWD is a run-time alternative
 * to JTAG.  Boards may support one or both.  There are also SWD-only chips,
 * (using SW-DP not SWJ-DP).
 *
 * Even boards that also support JTAG can benefit from SWD support, because
 * usually there's no way to access the SWO trace view mechanism in JTAG mode.
 * That is, trace access may require SWD support.
 *
 */

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

#include "arm.h"
#include "arm_adi_v5.h"
#include <helper/time_support.h>

#include <transport/transport.h>
#include <jtag/interface.h>

#include <jtag/swd.h>

/* YUK! - but this is currently a global.... */
extern struct jtag_interface *jtag_interface;

static int swd_finish_read(struct adiv5_dap *dap)
{
        const struct swd_driver *swd = jtag_interface->swd;
        int retval = ERROR_OK;
        if (dap->last_read != NULL) {
                retval = swd->read_reg(swd_cmd(true, false, DP_RDBUFF), dap->last_read);
                dap->last_read = NULL;
        }
        return retval;
}

static int (swd_queue_dp_write)(struct adiv5_dap *dap, unsigned reg,
                uint32_t data);

static int swd_queue_ap_abort(struct adiv5_dap *dap, uint8_t *ack)
{
        const struct swd_driver *swd = jtag_interface->swd;
        assert(swd);

        return swd->write_reg(swd_cmd(false,  false, DP_ABORT),
                STKCMPCLR | STKERRCLR | WDERRCLR | ORUNERRCLR);
}

/** Select the DP register bank matching bits 7:4 of reg. */
static int swd_queue_dp_bankselect(struct adiv5_dap *dap, unsigned reg)
{
        uint32_t select_dp_bank = (reg & 0x000000F0) >> 4;

        if (reg == DP_SELECT)
                return ERROR_OK;

        if (select_dp_bank == dap->dp_bank_value)
                return ERROR_OK;

        dap->dp_bank_value = select_dp_bank;
        select_dp_bank |= dap->ap_current | dap->ap_bank_value;

        return swd_queue_dp_write(dap, DP_SELECT, select_dp_bank);
}

static int swd_queue_dp_read(struct adiv5_dap *dap, unsigned reg,
                uint32_t *data)
{
        int retval;
        /* REVISIT status return vs ack ... */
        const struct swd_driver *swd = jtag_interface->swd;
        assert(swd);

        retval = swd_queue_dp_bankselect(dap, reg);
        if (retval != ERROR_OK)
                return retval;

        retval = swd->read_reg(swd_cmd(true,  false, reg), data);

        if (retval != ERROR_OK) {
                /* fault response */
                uint8_t ack = retval & 0xff;
                swd_queue_ap_abort(dap, &ack);
        }

        return retval;
}

static int swd_queue_idcode_read(struct adiv5_dap *dap,
                uint8_t *ack, uint32_t *data)
{
        int status = swd_queue_dp_read(dap, DP_IDCODE, data);
        if (status < 0)
                return status;
        *ack = status;
        /* ?? */
        return ERROR_OK;
}

static int (swd_queue_dp_write)(struct adiv5_dap *dap, unsigned reg,
                uint32_t data)
{
        int retval;
        /* REVISIT status return vs ack ... */
        const struct swd_driver *swd = jtag_interface->swd;
        assert(swd);

        retval = swd_finish_read(dap);
        if (retval != ERROR_OK)
                return retval;

        retval = swd_queue_dp_bankselect(dap, reg);
        if (retval != ERROR_OK)
                return retval;

        retval = swd->write_reg(swd_cmd(false,  false, reg), data);

        if (retval != ERROR_OK) {
                /* fault response */
                uint8_t ack = retval & 0xff;
                swd_queue_ap_abort(dap, &ack);
        }

        return retval;
}

/** Select the AP register bank matching bits 7:4 of reg. */
static int swd_queue_ap_bankselect(struct adiv5_dap *dap, unsigned reg)
{
        uint32_t select_ap_bank = reg & 0x000000F0;

        if (select_ap_bank == dap->ap_bank_value)
                return ERROR_OK;

        dap->ap_bank_value = select_ap_bank;
        select_ap_bank |= dap->ap_current | dap->dp_bank_value;

        return swd_queue_dp_write(dap, DP_SELECT, select_ap_bank);
}

static int (swd_queue_ap_read)(struct adiv5_dap *dap, unsigned reg,
                uint32_t *data)
{
        /* REVISIT status return ... */
        const struct swd_driver *swd = jtag_interface->swd;
        assert(swd);

        int retval = swd_queue_ap_bankselect(dap, reg);
        if (retval != ERROR_OK)
                return retval;

        retval = swd->read_reg(swd_cmd(true,  true, reg), dap->last_read);
        dap->last_read = data;

        if (retval != ERROR_OK) {
                /* fault response */
                uint8_t ack = retval & 0xff;
                swd_queue_ap_abort(dap, &ack);
                return retval;
        }

        return retval;
}

static int (swd_queue_ap_write)(struct adiv5_dap *dap, unsigned reg,
                uint32_t data)
{
        /* REVISIT status return ... */
        const struct swd_driver *swd = jtag_interface->swd;
        assert(swd);
        int retval;

        retval = swd_finish_read(dap);
        if (retval != ERROR_OK)
                return retval;

        retval = swd_queue_ap_bankselect(dap, reg);
        if (retval != ERROR_OK)
                return retval;

        retval = swd->write_reg(swd_cmd(false,  true, reg), data);

        if (retval != ERROR_OK) {
                /* fault response */
                uint8_t ack = retval & 0xff;
                swd_queue_ap_abort(dap, &ack);
        }

        return retval;
}

/** Executes all queued DAP operations. */
static int swd_run(struct adiv5_dap *dap)
{
        /* for now the SWD interface hard-wires a zero-size queue.  */

        int retval = swd_finish_read(dap);

        /* FIXME but we still need to check and scrub
         * any hardware errors ...
         */
        return retval;
}

const struct dap_ops swd_dap_ops = {
        .is_swd = true,

        .queue_idcode_read = swd_queue_idcode_read,
        .queue_dp_read = swd_queue_dp_read,
        .queue_dp_write = swd_queue_dp_write,
        .queue_ap_read = swd_queue_ap_read,
        .queue_ap_write = swd_queue_ap_write,
        .queue_ap_abort = swd_queue_ap_abort,
        .run = swd_run,
};

/*
 * This represents the bits which must be sent out on TMS/SWDIO to
 * switch a DAP implemented using an SWJ-DP module into SWD mode.
 * These bits are stored (and transmitted) LSB-first.
 *
 * See the DAP-Lite specification, section 2.2.5 for information
 * about making the debug link select SWD or JTAG.  (Similar info
 * is in a few other ARM documents.)
 */
static const uint8_t jtag2swd_bitseq[] = {
        /* More than 50 TCK/SWCLK cycles with TMS/SWDIO high,
         * putting both JTAG and SWD logic into reset state.
         */
        0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
        /* Switching sequence enables SWD and disables JTAG
         * NOTE: bits in the DP's IDCODE may expose the need for
         * an old/obsolete/deprecated sequence (0xb6 0xed).
         */
        0x9e, 0xe7,
        /* More than 50 TCK/SWCLK cycles with TMS/SWDIO high,
         * putting both JTAG and SWD logic into reset state.
         */
        0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
};

/**
 * Put the debug link into SWD mode, if the target supports it.
 * The link's initial mode may be either JTAG (for example,
 * with SWJ-DP after reset) or SWD.
 *
 * @param target Enters SWD mode (if possible).
 *
 * Note that targets using the JTAG-DP do not support SWD, and that
 * some targets which could otherwise support it may have have been
 * configured to disable SWD signaling
 *
 * @return ERROR_OK or else a fault code.
 */
int dap_to_swd(struct target *target)
{
        struct arm *arm = target_to_arm(target);
        int retval;

        LOG_DEBUG("Enter SWD mode");

        /* REVISIT it's ugly to need to make calls to a "jtag"
         * subsystem if the link may not be in JTAG mode...
         */

        retval =  jtag_add_tms_seq(8 * sizeof(jtag2swd_bitseq),
                        jtag2swd_bitseq, TAP_INVALID);
        if (retval == ERROR_OK)
                retval = jtag_execute_queue();

        /* set up the DAP's ops vector for SWD mode. */
        arm->dap->ops = &swd_dap_ops;

        return retval;
}

COMMAND_HANDLER(handle_swd_wcr)
{
        int retval;
        struct target *target = get_current_target(CMD_CTX);
        struct arm *arm = target_to_arm(target);
        struct adiv5_dap *dap = arm->dap;
        uint32_t wcr;
        unsigned trn, scale = 0;

        switch (CMD_ARGC) {
        /* no-args: just dump state */
        case 0:
                /*retval = swd_queue_dp_read(dap, DP_WCR, &wcr); */
                retval = dap_queue_dp_read(dap, DP_WCR, &wcr);
                if (retval == ERROR_OK)
                        dap->ops->run(dap);
                if (retval != ERROR_OK) {
                        LOG_ERROR("can't read WCR?");
                        return retval;
                }

                command_print(CMD_CTX,
                        "turnaround=%" PRIu32 ", prescale=%" PRIu32,
                        WCR_TO_TRN(wcr),
                        WCR_TO_PRESCALE(wcr));
        return ERROR_OK;

        case 2:         /* TRN and prescale */
                COMMAND_PARSE_NUMBER(uint, CMD_ARGV[1], scale);
                if (scale > 7) {
                        LOG_ERROR("prescale %d is too big", scale);
                        return ERROR_FAIL;
                }
                /* FALL THROUGH */

        case 1:         /* TRN only */
                COMMAND_PARSE_NUMBER(uint, CMD_ARGV[0], trn);
                if (trn < 1 || trn > 4) {
                        LOG_ERROR("turnaround %d is invalid", trn);
                        return ERROR_FAIL;
                }

                wcr = ((trn - 1) << 8) | scale;
                /* FIXME
                 * write WCR ...
                 * then, re-init adapter with new TRN
                 */
                LOG_ERROR("can't yet modify WCR");
                return ERROR_FAIL;

        default:        /* too many arguments */
                return ERROR_COMMAND_SYNTAX_ERROR;
        }
}

static const struct command_registration swd_commands[] = {
        {
                /*
                 * Set up SWD and JTAG targets identically, unless/until
                 * infrastructure improves ...  meanwhile, ignore all
                 * JTAG-specific stuff like IR length for SWD.
                 *
                 * REVISIT can we verify "just one SWD DAP" here/early?
                 */
                .name = "newdap",
                .jim_handler = jim_jtag_newtap,
                .mode = COMMAND_CONFIG,
                .help = "declare a new SWD DAP"
        },
        {
                .name = "wcr",
                .handler = handle_swd_wcr,
                .mode = COMMAND_ANY,
                .help = "display or update DAP's WCR register",
                .usage = "turnaround (1..4), prescale (0..7)",
        },

        /* REVISIT -- add a command for SWV trace on/off */
        COMMAND_REGISTRATION_DONE
};

static const struct command_registration swd_handlers[] = {
        {
                .name = "swd",
                .mode = COMMAND_ANY,
                .help = "SWD command group",
                .chain = swd_commands,
        },
        COMMAND_REGISTRATION_DONE
};

static int swd_select(struct command_context *ctx)
{
        int retval;

        retval = register_commands(ctx, NULL, swd_handlers);

        if (retval != ERROR_OK)
                return retval;

        const struct swd_driver *swd = jtag_interface->swd;

         /* be sure driver is in SWD mode; start
          * with hardware default TRN (1), it can be changed later
          */
        if (!swd || !swd->read_reg || !swd->write_reg || !swd->init) {
                LOG_DEBUG("no SWD driver?");
                return ERROR_FAIL;
        }

        retval = swd->init(1);
        if (retval != ERROR_OK) {
                LOG_DEBUG("can't init SWD driver");
                return retval;
        }

        /* force DAP into SWD mode (not JTAG) */
        /*retval = dap_to_swd(target);*/

        if (ctx->current_target) {
                /* force DAP into SWD mode (not JTAG) */
                struct target *target = get_current_target(ctx);
                retval = dap_to_swd(target);
        }

        return retval;
}

static int swd_init(struct command_context *ctx)
{
        struct target *target = get_current_target(ctx);
        struct arm *arm = target_to_arm(target);
        struct adiv5_dap *dap = arm->dap;
        uint32_t idcode;
        int status;

        /* Force the DAP's ops vector for SWD mode.
         * messy - is there a better way? */
        arm->dap->ops = &swd_dap_ops;

        /* FIXME validate transport config ... is the
         * configured DAP present (check IDCODE)?
         * Is *only* one DAP configured?
         *
         * MUST READ IDCODE
         */

 /* Note, debugport_init() does setup too */

        uint8_t ack;

        status = swd_queue_idcode_read(dap, &ack, &idcode);

        if (status == ERROR_OK)
                LOG_INFO("SWD IDCODE %#8.8" PRIx32, idcode);

        /* force clear all sticky faults */
        swd_queue_ap_abort(dap, &ack);

        /* this is a workaround to get polling working */
        jtag_add_reset(0, 0);

        return status;
}

static struct transport swd_transport = {
        .name = "swd",
        .select = swd_select,
        .init = swd_init,
};

static void swd_constructor(void) __attribute__((constructor));
static void swd_constructor(void)
{
        transport_register(&swd_transport);
}

/** Returns true if the current debug session
 * is using SWD as its transport.
 */
bool transport_is_swd(void)
{
        return get_current_transport() == &swd_transport;
}