Cortex-M3: DWT cleanup/fixes

Fix the watchpoint error checks, and do them in add(), not later
in set() when it's mostly too late.  Support the full range of
watchpoint sizes (1 to 32K bytes each), and check alignments.

Minor cleanup of DWT access:  shrink lines, use "+" for address
calculations, comment a few issues.  Add debug message reporting
DWT capabilities, matching the message for FBP, and some minor
code and spec review comments.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

1 files changed, 115 insertions, 56 deletions

diff --git a/src/target/cortex_m3.c b/src/target/cortex_m3.c
index 1afa29ff..ef57a4cd 100644
--- a/src/target/cortex_m3.c
+++ b/src/target/cortex_m3.c
@@ -223,9 +223,12 @@ static int cortex_m3_endreset_event(target_t *target)
 	/* Restore DWT registers */
 	for (i = 0; i < cortex_m3->dwt_num_comp; i++)
 	{
-		target_write_u32(target, dwt_list[i].dwt_comparator_address, dwt_list[i].comp);
-		target_write_u32(target, dwt_list[i].dwt_comparator_address | 0x4, dwt_list[i].mask);
-		target_write_u32(target, dwt_list[i].dwt_comparator_address | 0x8, dwt_list[i].function);
+		target_write_u32(target, dwt_list[i].dwt_comparator_address + 0,
+				dwt_list[i].comp);
+		target_write_u32(target, dwt_list[i].dwt_comparator_address + 4,
+				dwt_list[i].mask);
+		target_write_u32(target, dwt_list[i].dwt_comparator_address + 8,
+				dwt_list[i].function);
 	}
 	swjdp_transaction_endcheck(swjdp);
 
@@ -259,7 +262,7 @@ static int cortex_m3_examine_debug_reason(target_t *target)
 			target->debug_reason = DBG_REASON_WATCHPOINT;
 		else if (cortex_m3->nvic_dfsr & DFSR_VCATCH)
 			target->debug_reason = DBG_REASON_BREAKPOINT;
-		else /* EXTERNAL, HALTED, DWTTRAP w/o BKPT */
+		else /* EXTERNAL, HALTED */
 			target->debug_reason = DBG_REASON_UNDEFINED;
 	}
 
@@ -621,7 +624,7 @@ static int cortex_m3_resume(struct target_s *target, int current,
 		{
 			LOG_DEBUG("unset breakpoint at 0x%8.8" PRIx32 " (ID: %d)",
 					  breakpoint->address,
-					  breakpoint->unique_id );
+					  breakpoint->unique_id);
 			cortex_m3_unset_breakpoint(target, breakpoint);
 			cortex_m3_single_step_core(target);
 			cortex_m3_set_breakpoint(target, breakpoint);
@@ -1036,6 +1039,7 @@ cortex_m3_remove_breakpoint(struct target_s *target, breakpoint_t *breakpoint)
 	armv7m_common_t *armv7m = target->arch_info;
 	cortex_m3_common_t *cortex_m3 = armv7m->arch_info;
 
+	/* REVISIT why check? FBP can be updated with core running ... */
 	if (target->state != TARGET_HALTED)
 	{
 		LOG_WARNING("target not halted");
@@ -1067,52 +1071,63 @@ cortex_m3_set_watchpoint(struct target_s *target, watchpoint_t *watchpoint)
 	/* get pointers to arch-specific information */
 	armv7m_common_t *armv7m = target->arch_info;
 	cortex_m3_common_t *cortex_m3 = armv7m->arch_info;
-	cortex_m3_dwt_comparator_t * comparator_list = cortex_m3->dwt_comparator_list;
 
-	if (watchpoint->set)
-	{
-		LOG_WARNING("watchpoint (%d) already set", watchpoint->unique_id );
-		return ERROR_OK;
+	/* watchpoint params were validated earlier */
+	mask = 0;
+	temp = watchpoint->length;
+	while (temp) {
+		temp >>= 1;
+		mask++;
 	}
+	mask--;
+
+	/* REVISIT Don't fully trust these "not used" records ... users
+	 * may set up breakpoints by hand, e.g. dual-address data value
+	 * watchpoint using comparator #1; comparator #0 matching cycle
+	 * count; send data trace info through ITM and TPIU; etc
+	 */
+	cortex_m3_dwt_comparator_t *comparator;
 
-	if (watchpoint->mask == 0xffffffffu)
+	for (comparator = cortex_m3->dwt_comparator_list;
+			comparator->used && dwt_num < cortex_m3->dwt_num_comp;
+			comparator++, dwt_num++)
+		continue;
+	if (dwt_num >= cortex_m3->dwt_num_comp)
 	{
-		while (comparator_list[dwt_num].used && (dwt_num < cortex_m3->dwt_num_comp))
-			dwt_num++;
-		if (dwt_num >= cortex_m3->dwt_num_comp)
-		{
-			LOG_DEBUG("ERROR Can not find free DWT Comparator");
-			LOG_WARNING("ERROR Can not find free DWT Comparator");
-			return -1;
-		}
-		watchpoint->set = dwt_num + 1;
-		mask = 0;
-		temp = watchpoint->length;
-		while (temp > 1)
-		{
-			temp = temp / 2;
-			mask++;
-		}
-		comparator_list[dwt_num].used = 1;
-		comparator_list[dwt_num].comp = watchpoint->address;
-		comparator_list[dwt_num].mask = mask;
-		comparator_list[dwt_num].function = watchpoint->rw + 5;
-		target_write_u32(target, comparator_list[dwt_num].dwt_comparator_address, comparator_list[dwt_num].comp);
-		target_write_u32(target, comparator_list[dwt_num].dwt_comparator_address | 0x4, comparator_list[dwt_num].mask);
-		target_write_u32(target, comparator_list[dwt_num].dwt_comparator_address | 0x8, comparator_list[dwt_num].function);
-		LOG_DEBUG("dwt_num %i 0x%" PRIx32 " 0x%" PRIx32 " 0x%" PRIx32 "", dwt_num, comparator_list[dwt_num].comp, comparator_list[dwt_num].mask, comparator_list[dwt_num].function);
+		LOG_ERROR("Can not find free DWT Comparator");
+		return ERROR_FAIL;
 	}
-	else
-	{
-		/* Move this test to add_watchpoint */
-		LOG_WARNING("Cannot watch data values (id: %d)",
-				  watchpoint->unique_id );
-		return ERROR_OK;
+	comparator->used = 1;
+	watchpoint->set = dwt_num + 1;
+
+	comparator->comp = watchpoint->address;
+	target_write_u32(target, comparator->dwt_comparator_address + 0,
+			comparator->comp);
+
+	comparator->mask = mask;
+	target_write_u32(target, comparator->dwt_comparator_address + 4,
+			comparator->mask);
+
+	switch (watchpoint->rw) {
+	case WPT_READ:
+		comparator->function = 5;
+		break;
+	case WPT_WRITE:
+		comparator->function = 6;
+		break;
+	case WPT_ACCESS:
+		comparator->function = 7;
+		break;
 	}
-	LOG_DEBUG("Watchpoint (ID: %d) address: 0x%08" PRIx32 " set=%d ",
-			  watchpoint->unique_id, watchpoint->address, watchpoint->set );
-	return ERROR_OK;
+	target_write_u32(target, comparator->dwt_comparator_address + 8,
+			comparator->function);
 
+	LOG_DEBUG("Watchpoint (ID %d) DWT%d 0x%08x 0x%x 0x%05x",
+			watchpoint->unique_id, dwt_num,
+			(unsigned) comparator->comp,
+			(unsigned) comparator->mask,
+			(unsigned) comparator->function);
+	return ERROR_OK;
 }
 
 static int
@@ -1121,28 +1136,33 @@ cortex_m3_unset_watchpoint(struct target_s *target, watchpoint_t *watchpoint)
 	/* get pointers to arch-specific information */
 	armv7m_common_t *armv7m = target->arch_info;
 	cortex_m3_common_t *cortex_m3 = armv7m->arch_info;
-	cortex_m3_dwt_comparator_t * comparator_list = cortex_m3->dwt_comparator_list;
+	cortex_m3_dwt_comparator_t *comparator;
 	int dwt_num;
 
 	if (!watchpoint->set)
 	{
-		LOG_WARNING("watchpoint (wpid: %d) not set", watchpoint->unique_id );
+		LOG_WARNING("watchpoint (wpid: %d) not set",
+				watchpoint->unique_id);
 		return ERROR_OK;
 	}
 
-	LOG_DEBUG("Watchpoint (ID: %d) address: 0x%08" PRIx32 " set=%d ",
-			  watchpoint->unique_id, watchpoint->address,watchpoint->set );
-
 	dwt_num = watchpoint->set - 1;
 
+	LOG_DEBUG("Watchpoint (ID %d) DWT%d address: 0x%08x clear",
+			watchpoint->unique_id, dwt_num,
+			(unsigned) watchpoint->address);
+
 	if ((dwt_num < 0) || (dwt_num >= cortex_m3->dwt_num_comp))
 	{
 		LOG_DEBUG("Invalid DWT Comparator number in watchpoint");
 		return ERROR_OK;
 	}
-	comparator_list[dwt_num].used = 0;
-	comparator_list[dwt_num].function = 0;
-	target_write_u32(target, comparator_list[dwt_num].dwt_comparator_address | 0x8, comparator_list[dwt_num].function);
+
+	comparator = cortex_m3->dwt_comparator_list + dwt_num;
+	comparator->used = 0;
+	comparator->function = 0;
+	target_write_u32(target, comparator->dwt_comparator_address + 8,
+			comparator->function);
 
 	watchpoint->set = 0;
 
@@ -1156,6 +1176,7 @@ cortex_m3_add_watchpoint(struct target_s *target, watchpoint_t *watchpoint)
 	armv7m_common_t *armv7m = target->arch_info;
 	cortex_m3_common_t *cortex_m3 = armv7m->arch_info;
 
+	/* REVISIT why check? DWT can be updated with core running ... */
 	if (target->state != TARGET_HALTED)
 	{
 		LOG_WARNING("target not halted");
@@ -1164,11 +1185,41 @@ cortex_m3_add_watchpoint(struct target_s *target, watchpoint_t *watchpoint)
 
 	if (cortex_m3->dwt_comp_available < 1)
 	{
+		LOG_DEBUG("no comparators?");
 		return ERROR_TARGET_RESOURCE_NOT_AVAILABLE;
 	}
 
-	if ((watchpoint->length != 1) && (watchpoint->length != 2) && (watchpoint->length != 4))
-	{
+	/* hardware doesn't support data value masking */
+	if (watchpoint->mask != ~(uint32_t)0) {
+		LOG_DEBUG("watchpoint value masks not supported");
+		return ERROR_TARGET_RESOURCE_NOT_AVAILABLE;
+	}
+
+	/* hardware allows address masks of up to 32K */
+	unsigned mask;
+
+	for (mask = 0; mask < 16; mask++) {
+		if ((1 << mask) == watchpoint->length)
+			break;
+	}
+	if (mask == 16) {
+		LOG_DEBUG("unsupported watchpoint length");
+		return ERROR_TARGET_RESOURCE_NOT_AVAILABLE;
+	}
+	if (watchpoint->address & ((1 << mask) - 1)) {
+		LOG_DEBUG("watchpoint address is unaligned");
+		return ERROR_TARGET_RESOURCE_NOT_AVAILABLE;
+	}
+
+	/* Caller doesn't seem to be able to describe watching for data
+	 * values of zero; that flags "no value".
+	 *
+	 * REVISIT This DWT may well be able to watch for specific data
+	 * values.  Requires comparator #1 to set DATAVMATCH and match
+	 * the data, and another comparator (DATAVADDR0) matching addr.
+	 */
+	if (watchpoint->value) {
+		LOG_DEBUG("data value watchpoint not YET supported");
 		return ERROR_TARGET_RESOURCE_NOT_AVAILABLE;
 	}
 
@@ -1185,6 +1236,7 @@ cortex_m3_remove_watchpoint(struct target_s *target, watchpoint_t *watchpoint)
 	armv7m_common_t *armv7m = target->arch_info;
 	cortex_m3_common_t *cortex_m3 = armv7m->arch_info;
 
+	/* REVISIT why check? DWT can be updated with core running ... */
 	if (target->state != TARGET_HALTED)
 	{
 		LOG_WARNING("target not halted");
@@ -1494,11 +1546,18 @@ static int cortex_m3_examine(struct target_s *target)
 		target_read_u32(target, DWT_CTRL, &dwtcr);
 		cortex_m3->dwt_num_comp = (dwtcr >> 28) & 0xF;
 		cortex_m3->dwt_comp_available = cortex_m3->dwt_num_comp;
-		cortex_m3->dwt_comparator_list = calloc(cortex_m3->dwt_num_comp, sizeof(cortex_m3_dwt_comparator_t));
+		cortex_m3->dwt_comparator_list = calloc(
+				cortex_m3->dwt_num_comp,
+				sizeof(cortex_m3_dwt_comparator_t));
 		for (i = 0; i < cortex_m3->dwt_num_comp; i++)
 		{
-			cortex_m3->dwt_comparator_list[i].dwt_comparator_address = DWT_COMP0 + 0x10 * i;
+			cortex_m3->dwt_comparator_list[i]
+				.dwt_comparator_address = DWT_COMP0 + 0x10 * i;
 		}
+		if (cortex_m3->dwt_num_comp)
+			LOG_DEBUG("DWT dwtcr 0x%" PRIx32 ", comp %d, watch%s",
+				dwtcr, cortex_m3->dwt_num_comp,
+				(dwtcr & (0xf << 24)) ? " only" : "/trigger");
 	}
 
 	return ERROR_OK;