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target: improve robustness of reset command

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Before this change jim_target_reset() checked examined state of a target
and failed without calling .assert_reset in particular target layer
(and without comprehensible warning to user).
Cortex-M target (which refuses access to DP under active SRST):
If connection is lost then reset process fails before asserting SRST
and connection with MCU is not restored.
This resulted in:
1) A lot of Cortex-M MCUs required use of reset button or cycling power
after firmware blocked SWD access somehow (sleep, misconfigured clock etc).
If firmware blocks SWD access early during initialization, a MCU could
become completely inaccessible by SWD.
2) If OpenOCD is (re)started and a MCU is in a broken state unresponsive
to SWD, reset command does not work even if it could help to restore communication.
Hopefully this scenario is not possible under full JTAG.

jim_target_reset() in target.c now does not check examined state
and delegates this task to a particular target. All targets have been checked
and xx_assert_reset() (or xx_deassert_reset()) procedures were changed
to check examined state if needed. Targets except arm11, cortex_a and cortex_m
just fail if target is not examined although it may be possible to use
at least hw reset. Left as TODO for developers familiar with these targets.

cortex_m_assert_reset(): memory access errors are stored
instead of immediate returning them to a higher level.
Errors from less important reads/writes are ignored.
Requested reset always leads to a configured action.

arm11_assert_reset() just asserts hw reset in case of not examined target.
cortex_a_assert_reset() works as usual in case of not examined target.

Change-Id: I84fa869f4f58e2fa83b6ea75de84440d9dc3d929
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: http://openocd.zylin.com/2606
Tested-by: jenkins
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>
Reviewed-by: Paul Fertser <fercerpav@gmail.com>
This commit is contained in:
Tomas Vanek
2015-03-15 19:09:15 +01:00
committed by Freddie Chopin
parent baf08b0a1a
commit 8825804273
9 changed files with 89 additions and 49 deletions
Download Patch File Download Diff File Expand all files Collapse all files

39
src/target/arm11.c
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@@ -694,21 +694,32 @@ static int arm11_assert_reset(struct target *target)
{
struct arm11_common *arm11 = target_to_arm11(target);
/* optionally catch reset vector */
if (target->reset_halt && !(arm11->vcr & 1))
CHECK_RETVAL(arm11_sc7_set_vcr(arm11, arm11->vcr | 1));
/* Issue some kind of warm reset. */
if (target_has_event_action(target, TARGET_EVENT_RESET_ASSERT))
target_handle_event(target, TARGET_EVENT_RESET_ASSERT);
else if (jtag_get_reset_config() & RESET_HAS_SRST) {
/* REVISIT handle "pulls" cases, if there's
* hardware that needs them to work.
*/
jtag_add_reset(0, 1);
if (!(target_was_examined(target))) {
if (jtag_get_reset_config() & RESET_HAS_SRST)
jtag_add_reset(0, 1);
else {
LOG_WARNING("Reset is not asserted because the target is not examined.");
LOG_WARNING("Use a reset button or power cycle the target.");
return ERROR_TARGET_NOT_EXAMINED;
}
} else {
LOG_ERROR("%s: how to reset?", target_name(target));
return ERROR_FAIL;
/* optionally catch reset vector */
if (target->reset_halt && !(arm11->vcr & 1))
CHECK_RETVAL(arm11_sc7_set_vcr(arm11, arm11->vcr | 1));
/* Issue some kind of warm reset. */
if (target_has_event_action(target, TARGET_EVENT_RESET_ASSERT))
target_handle_event(target, TARGET_EVENT_RESET_ASSERT);
else if (jtag_get_reset_config() & RESET_HAS_SRST) {
/* REVISIT handle "pulls" cases, if there's
* hardware that needs them to work.
*/
jtag_add_reset(0, 1);
} else {
LOG_ERROR("%s: how to reset?", target_name(target));
return ERROR_FAIL;
}
}
/* registers are now invalid */