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target/cortex_m: cumulate DHCSR sticky bits
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DCB DHCSR register contains S_RETIRE_ST and S_RESET_ST bits cleared
on a read.

The change introduces a helper function cortex_m_cumulate_dhcsr_sticky().
Call this function each time DHCSR is read to preserve S_RESET_ST state
in the case of a reset event was detected.

Introduce cortex_m_read_dhcsr_atomic_sticky() convenience helper to
read DHCSR, store it to cortex_m->dcb_dhcsr and cumulate sticky bits.

The cumulated state of S_RESET_ST is read and cleared in cortex_m_poll()

Change-Id: Ib679599f850fd219fb9418c6ff32eed7cf5740da
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: https://review.openocd.org/c/openocd/+/6180
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-by: Tarek BOCHKATI <tarek.bouchkati@gmail.com>
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@tom-van
tom-van committed Nov 18, 2021
1 parent 111dcbe commit 0dcf95c
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Showing 2 changed files with 54 additions and 16 deletions.
69 changes: 53 additions & 16 deletions src/target/cortex_m.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -118,6 +118,33 @@ static int cortex_m_store_core_reg_u32(struct target *target,
uint32_t num, uint32_t value);
static void cortex_m_dwt_free(struct target *target);

/** DCB DHCSR register contains S_RETIRE_ST and S_RESET_ST bits cleared
* on a read. Call this helper function each time DHCSR is read
* to preserve S_RESET_ST state in case of a reset event was detected.
*/
static inline void cortex_m_cumulate_dhcsr_sticky(struct cortex_m_common *cortex_m,
uint32_t dhcsr)
{
cortex_m->dcb_dhcsr_cumulated_sticky |= dhcsr;
}

/** Read DCB DHCSR register to cortex_m->dcb_dhcsr and cumulate
* sticky bits in cortex_m->dcb_dhcsr_cumulated_sticky
*/
static int cortex_m_read_dhcsr_atomic_sticky(struct target *target)
{
struct cortex_m_common *cortex_m = target_to_cm(target);
struct armv7m_common *armv7m = target_to_armv7m(target);

int retval = mem_ap_read_atomic_u32(armv7m->debug_ap, DCB_DHCSR,
&cortex_m->dcb_dhcsr);
if (retval != ERROR_OK)
return retval;

cortex_m_cumulate_dhcsr_sticky(cortex_m, cortex_m->dcb_dhcsr);
return ERROR_OK;
}

static int cortex_m_load_core_reg_u32(struct target *target,
uint32_t regsel, uint32_t *value)
{
Expand Down Expand Up @@ -362,11 +389,12 @@ static int cortex_m_endreset_event(struct target *target)
if (retval != ERROR_OK)
return retval;

/* Enable debug requests */
retval = mem_ap_read_atomic_u32(armv7m->debug_ap, DCB_DHCSR, &cortex_m->dcb_dhcsr);
retval = cortex_m_read_dhcsr_atomic_sticky(target);
if (retval != ERROR_OK)
return retval;

if (!(cortex_m->dcb_dhcsr & C_DEBUGEN)) {
/* Enable debug requests */
retval = cortex_m_write_debug_halt_mask(target, 0, C_HALT | C_STEP | C_MASKINTS);
if (retval != ERROR_OK)
return retval;
Expand Down Expand Up @@ -428,7 +456,9 @@ static int cortex_m_endreset_event(struct target *target)
register_cache_invalidate(armv7m->arm.core_cache);

/* make sure we have latest dhcsr flags */
retval = mem_ap_read_atomic_u32(armv7m->debug_ap, DCB_DHCSR, &cortex_m->dcb_dhcsr);
retval = cortex_m_read_dhcsr_atomic_sticky(target);
if (retval != ERROR_OK)
return retval;

return retval;
}
Expand Down Expand Up @@ -552,7 +582,8 @@ static int cortex_m_debug_entry(struct target *target)
cortex_m_set_maskints_for_halt(target);

cortex_m_clear_halt(target);
retval = mem_ap_read_atomic_u32(armv7m->debug_ap, DCB_DHCSR, &cortex_m->dcb_dhcsr);

retval = cortex_m_read_dhcsr_atomic_sticky(target);
if (retval != ERROR_OK)
return retval;

Expand Down Expand Up @@ -636,7 +667,7 @@ static int cortex_m_poll(struct target *target)
struct armv7m_common *armv7m = &cortex_m->armv7m;

/* Read from Debug Halting Control and Status Register */
retval = mem_ap_read_atomic_u32(armv7m->debug_ap, DCB_DHCSR, &cortex_m->dcb_dhcsr);
retval = cortex_m_read_dhcsr_atomic_sticky(target);
if (retval != ERROR_OK) {
target->state = TARGET_UNKNOWN;
return retval;
Expand All @@ -657,12 +688,13 @@ static int cortex_m_poll(struct target *target)
detected_failure = ERROR_FAIL;

/* refresh status bits */
retval = mem_ap_read_atomic_u32(armv7m->debug_ap, DCB_DHCSR, &cortex_m->dcb_dhcsr);
retval = cortex_m_read_dhcsr_atomic_sticky(target);
if (retval != ERROR_OK)
return retval;
}

if (cortex_m->dcb_dhcsr & S_RESET_ST) {
if (cortex_m->dcb_dhcsr_cumulated_sticky & S_RESET_ST) {
cortex_m->dcb_dhcsr_cumulated_sticky &= ~S_RESET_ST;
if (target->state != TARGET_RESET) {
target->state = TARGET_RESET;
LOG_INFO("%s: external reset detected", target_name(target));
Expand Down Expand Up @@ -709,7 +741,12 @@ static int cortex_m_poll(struct target *target)
}

if (target->state == TARGET_UNKNOWN) {
/* check if processor is retiring instructions or sleeping */
/* Check if processor is retiring instructions or sleeping.
* Unlike S_RESET_ST here we test if the target *is* running now,
* not if it has been running (possibly in the past). Instructions are
* typically processed much faster than OpenOCD polls DHCSR so S_RETIRE_ST
* is read always 1. That's the reason not to use dcb_dhcsr_cumulated_sticky.
*/
if (cortex_m->dcb_dhcsr & S_RETIRE_ST || cortex_m->dcb_dhcsr & S_SLEEP) {
target->state = TARGET_RUNNING;
retval = ERROR_OK;
Expand Down Expand Up @@ -811,7 +848,7 @@ static int cortex_m_soft_reset_halt(struct target *target)
register_cache_invalidate(cortex_m->armv7m.arm.core_cache);

while (timeout < 100) {
retval = mem_ap_read_atomic_u32(armv7m->debug_ap, DCB_DHCSR, &cortex_m->dcb_dhcsr);
retval = cortex_m_read_dhcsr_atomic_sticky(target);
if (retval == ERROR_OK) {
retval = mem_ap_read_atomic_u32(armv7m->debug_ap, NVIC_DFSR,
&cortex_m->nvic_dfsr);
Expand Down Expand Up @@ -1076,9 +1113,7 @@ static int cortex_m_step(struct target *target, int current,

/* Wait for pending handlers to complete or timeout */
do {
retval = mem_ap_read_atomic_u32(armv7m->debug_ap,
DCB_DHCSR,
&cortex_m->dcb_dhcsr);
retval = cortex_m_read_dhcsr_atomic_sticky(target);
if (retval != ERROR_OK) {
target->state = TARGET_UNKNOWN;
return retval;
Expand Down Expand Up @@ -1113,7 +1148,7 @@ static int cortex_m_step(struct target *target, int current,
}
}

retval = mem_ap_read_atomic_u32(armv7m->debug_ap, DCB_DHCSR, &cortex_m->dcb_dhcsr);
retval = cortex_m_read_dhcsr_atomic_sticky(target);
if (retval != ERROR_OK)
return retval;

Expand Down Expand Up @@ -1191,8 +1226,8 @@ static int cortex_m_assert_reset(struct target *target)
}

/* Enable debug requests */
int retval;
retval = mem_ap_read_atomic_u32(armv7m->debug_ap, DCB_DHCSR, &cortex_m->dcb_dhcsr);
int retval = cortex_m_read_dhcsr_atomic_sticky(target);

/* Store important errors instead of failing and proceed to reset assert */

if (retval != ERROR_OK || !(cortex_m->dcb_dhcsr & C_DEBUGEN))
Expand Down Expand Up @@ -2136,11 +2171,13 @@ int cortex_m_examine(struct target *target)
armv7m->debug_ap->tar_autoincr_block = (1 << 12);
}

/* Enable debug requests */
retval = target_read_u32(target, DCB_DHCSR, &cortex_m->dcb_dhcsr);
if (retval != ERROR_OK)
return retval;
cortex_m_cumulate_dhcsr_sticky(cortex_m, cortex_m->dcb_dhcsr);

if (!(cortex_m->dcb_dhcsr & C_DEBUGEN)) {
/* Enable debug requests */
uint32_t dhcsr = (cortex_m->dcb_dhcsr | C_DEBUGEN) & ~(C_HALT | C_STEP | C_MASKINTS);

retval = target_write_u32(target, DCB_DHCSR, DBGKEY | (dhcsr & 0x0000FFFFUL));
Expand Down
1 change: 1 addition & 0 deletions src/target/cortex_m.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -213,6 +213,7 @@ struct cortex_m_common {

/* Context information */
uint32_t dcb_dhcsr;
uint32_t dcb_dhcsr_cumulated_sticky;
uint32_t nvic_dfsr; /* Debug Fault Status Register - shows reason for debug halt */
uint32_t nvic_icsr; /* Interrupt Control State Register - shows active and pending IRQ */

Expand Down

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