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Fixed SAM D20 support with reset attached. 

monitor connect_srst enable can be used to connect to targets that re-use the SWCLK pin
This commit is contained in:
Richard Eoin Meadows 2014-08-22 21:47:47 +01:00 committed by Gareth McMullin
parent e75798f201
commit 2a444ab1fb
1 changed files with 25 additions and 8 deletions
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33
src/samd20.c
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@ -235,8 +235,21 @@ samd20_reset(struct target_s *target)
{
ADIv5_AP_t *ap = adiv5_target_ap(target);
jtagtap_srst(true);
jtagtap_srst(false);
/**
* SRST is not asserted here as it appears to reset the adiv5
* logic, meaning that subsequent adiv5_* calls PLATFORM_FATAL_ERROR.
*
* This is ok as normally you can just connect the debugger and go,
* but if that's not possible (protection or SWCLK being used for
* something else) then having SWCLK low on reset should get you
* debug access (cold-plugging). TODO: Confirm this
*
* See the SAM D20 datasheet §12.6 Debug Operation for more
* details.
*
* jtagtap_srst(true);
* jtagtap_srst(false);
*/
/* Read DHCSR here to clear S_RESET_ST bit before reset */
adiv5_ap_mem_read(ap, CORTEXM_DHCSR);
@ -309,13 +322,17 @@ bool samd20_probe(struct target_s *target)
target->flash_write = samd20_flash_write;
target_add_commands(target, samd20_cmd_list, "SAMD20");
/* Release the target from extended reset to make attach possible */
if (adiv5_ap_mem_read(ap, SAMD20_DSU_CTRLSTAT) &
SAMD20_STATUSA_CRSTEXT) {
/* If we're not in reset here */
if (!connect_assert_srst) {
/* We'll have to release the target from
* extended reset to make attach possible */
if (adiv5_ap_mem_read(ap, SAMD20_DSU_CTRLSTAT) &
SAMD20_STATUSA_CRSTEXT) {
/* Write bit to clear from extended reset */
adiv5_ap_mem_write(ap, SAMD20_DSU_CTRLSTAT,
SAMD20_STATUSA_CRSTEXT);
/* Write bit to clear from extended reset */
adiv5_ap_mem_write(ap, SAMD20_DSU_CTRLSTAT,
SAMD20_STATUSA_CRSTEXT);
}
}
return true;