1 /***************************************************************************
3 * Copyright (C) 2010 by David Brownell
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the
17 * Free Software Foundation, Inc.,
18 * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
19 ***************************************************************************/
23 * Utilities to support ARM "Serial Wire Debug" (SWD), a low pin-count debug
24 * link protocol used in cases where JTAG is not wanted. This is coupled to
25 * recent versions of ARM's "CoreSight" debug framework. This specific code
26 * is a transport level interface, with "target/arm_adi_v5.[hc]" code
27 * understanding operation semantics, shared with the JTAG transport.
29 * Single-DAP support only.
31 * for details, see "ARM IHI 0031A"
32 * ARM Debug Interface v5 Architecture Specification
33 * especially section 5.3 for SWD protocol
35 * On many chips (most current Cortex-M3 parts) SWD is a run-time alternative
36 * to JTAG. Boards may support one or both. There are also SWD-only chips,
37 * (using SW-DP not SWJ-DP).
39 * Even boards that also support JTAG can benefit from SWD support, because
40 * usually there's no way to access the SWO trace view mechanism in JTAG mode.
41 * That is, trace access may require SWD support.
50 #include "arm_adi_v5.h"
51 #include <helper/time_support.h>
53 #include <jtag/transport.h>
54 #include <jtag/interface.h>
60 static int swd_queue_dp_read(struct adiv5_dap
*dap
, unsigned reg
,
63 // REVISIT status return vs ack ...
64 return swd
->read_reg(swd_cmd(true, false, reg
), data
);
67 static int swd_queue_idcode_read(struct adiv5_dap
*dap
,
68 uint8_t *ack
, uint32_t *data
)
70 int status
= swd_queue_dp_read(dap
, DP_IDCODE
, data
);
78 static int (swd_queue_dp_write
)(struct adiv5_dap
*dap
, unsigned reg
,
81 // REVISIT status return vs ack ...
82 return swd
->write_reg(swd_cmd(false, false, reg
), data
);
86 static int (swd_queue_ap_read
)(struct adiv5_dap
*dap
, unsigned reg
,
90 // REVISIT status return ...
91 return swd
->read_reg(swd_cmd(true, true, reg
), data
);
94 static int (swd_queue_ap_write
)(struct adiv5_dap
*dap
, unsigned reg
,
98 // REVISIT status return ...
99 return swd
->write_reg(swd_cmd(false, true, reg
), data
);
102 static int (swd_queue_ap_abort
)(struct adiv5_dap
*dap
, uint8_t *ack
)
107 /** Executes all queued DAP operations. */
108 static int swd_run(struct adiv5_dap
*dap
)
110 /* for now the SWD interface hard-wires a zero-size queue. */
112 /* FIXME but we still need to check and scrub
113 * any hardware errors ...
118 const struct dap_ops swd_dap_ops
= {
121 .queue_idcode_read
= swd_queue_idcode_read
,
122 .queue_dp_read
= swd_queue_dp_read
,
123 .queue_dp_write
= swd_queue_dp_write
,
124 .queue_ap_read
= swd_queue_ap_read
,
125 .queue_ap_write
= swd_queue_ap_write
,
126 .queue_ap_abort
= swd_queue_ap_abort
,
131 * This represents the bits which must be sent out on TMS/SWDIO to
132 * switch a DAP implemented using an SWJ-DP module into SWD mode.
133 * These bits are stored (and transmitted) LSB-first.
135 * See the DAP-Lite specification, section 2.2.5 for information
136 * about making the debug link select SWD or JTAG. (Similar info
137 * is in a few other ARM documents.)
139 static const uint8_t jtag2swd_bitseq
[] = {
140 /* More than 50 TCK/SWCLK cycles with TMS/SWDIO high,
141 * putting both JTAG and SWD logic into reset state.
143 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
144 /* Switching sequence enables SWD and disables JTAG
145 * NOTE: bits in the DP's IDCODE may expose the need for
146 * an old/obsolete/deprecated sequence (0xb6 0xed).
149 /* More than 50 TCK/SWCLK cycles with TMS/SWDIO high,
150 * putting both JTAG and SWD logic into reset state.
152 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
156 * Put the debug link into SWD mode, if the target supports it.
157 * The link's initial mode may be either JTAG (for example,
158 * with SWJ-DP after reset) or SWD.
160 * @param target Enters SWD mode (if possible).
162 * Note that targets using the JTAG-DP do not support SWD, and that
163 * some targets which could otherwise support it may have have been
164 * configured to disable SWD signaling
166 * @return ERROR_OK or else a fault code.
168 int dap_to_swd(struct target
*target
)
170 struct arm
*arm
= target_to_arm(target
);
173 LOG_DEBUG("Enter SWD mode");
175 /* REVISIT it's ugly to need to make calls to a "jtag"
176 * subsystem if the link may not be in JTAG mode...
179 retval
= jtag_add_tms_seq(8 * sizeof(jtag2swd_bitseq
),
180 jtag2swd_bitseq
, TAP_INVALID
);
181 if (retval
== ERROR_OK
)
182 retval
= jtag_execute_queue();
184 /* set up the DAP's ops vector for SWD mode. */
185 arm
->dap
->ops
= &swd_dap_ops
;
192 COMMAND_HANDLER(handle_swd_wcr
)
195 struct target
*target
= get_current_target(CMD_CTX
);
196 struct arm
*arm
= target_to_arm(target
);
197 struct adiv5_dap
*dap
= arm
->dap
;
199 unsigned trn
, scale
= 0;
203 /* no-args: just dump state */
205 //retval = swd_queue_dp_read(dap, DP_WCR, &wcr);
206 retval
= dap_queue_dp_read(dap
, DP_WCR
, &wcr
);
207 if (retval
== ERROR_OK
)
209 if (retval
!= ERROR_OK
) {
210 LOG_ERROR("can't read WCR?");
214 command_print(CMD_CTX
,
215 "turnaround=%d, prescale=%d",
217 WCR_TO_PRESCALE(wcr
));
220 case 2: /* TRN and prescale */
221 COMMAND_PARSE_NUMBER(uint
, CMD_ARGV
[1], scale
);
223 LOG_ERROR("prescale %d is too big", scale
);
228 case 1: /* TRN only */
229 COMMAND_PARSE_NUMBER(uint
, CMD_ARGV
[0], trn
);
230 if (trn
< 1 || trn
> 4) {
231 LOG_ERROR("turnaround %d is invalid", trn
);
235 wcr
= ((trn
- 1) << 8) | scale
;
238 * then, re-init adapter with new TRN
240 LOG_ERROR("can't yet modify WCR");
243 default: /* too many arguments */
244 return ERROR_COMMAND_SYNTAX_ERROR
;
248 static const struct command_registration swd_commands
[] = {
251 * Set up SWD and JTAG targets identically, unless/until
252 * infrastructure improves ... meanwhile, ignore all
253 * JTAG-specific stuff like IR length for SWD.
255 * REVISIT can we verify "just one SWD DAP" here/early?
258 .jim_handler
= jim_jtag_newtap
,
259 .mode
= COMMAND_CONFIG
,
260 .help
= "declare a new SWD DAP"
264 .handler
= handle_swd_wcr
,
266 .help
= "display or update DAP's WCR register",
267 .usage
= "turnaround (1..4), prescale (0..7)",
270 /* REVISIT -- add a command for SWV trace on/off */
271 COMMAND_REGISTRATION_DONE
274 static const struct command_registration swd_handlers
[] = {
278 .help
= "SWD command group",
279 .chain
= swd_commands
,
281 COMMAND_REGISTRATION_DONE
284 static int swd_select(struct command_context
*ctx
)
286 struct target
*target
= get_current_target(ctx
);
289 retval
= register_commands(ctx
, NULL
, swd_handlers
);
291 if (retval
!= ERROR_OK
)
294 /* be sure driver is in SWD mode; start
295 * with hardware default TRN (1), it can be changed later
297 if (!swd
|| !swd
->read_reg
|| !swd
->write_reg
|| !swd
->init
) {
298 LOG_DEBUG("no SWD driver?");
302 retval
= swd
->init(1);
303 if (retval
!= ERROR_OK
) {
304 LOG_DEBUG("can't init SWD driver");
308 /* force DAP into SWD mode (not JTAG) */
309 retval
= dap_to_swd(target
);
314 static int swd_init(struct command_context
*ctx
)
316 struct target
*target
= get_current_target(ctx
);
317 struct arm
*arm
= target_to_arm(target
);
318 struct adiv5_dap
*dap
= arm
->dap
;
323 /* FIXME validate transport config ... is the
324 * configured DAP present (check IDCODE)?
325 * Is *only* one DAP configured?
330 /* Note, debugport_init() does setup too */
334 status
= swd_queue_idcode_read(dap
, &ack
, &idcode
);
336 if (status
== ERROR_OK
)
337 LOG_INFO("SWD IDCODE %#8.8x", idcode
);
343 static struct transport swd_transport
= {
345 .select
= swd_select
,
349 static void swd_constructor(void) __attribute__((constructor
));
350 static void swd_constructor(void)
352 transport_register(&swd_transport
);
355 /** Returns true if the current debug session
356 * is using SWD as its transport.
358 bool transport_is_swd(void)
360 return get_current_transport() == &swd_transport
;
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