target/riscv: Add support for external triggers

Add support for associating a halt/resume group with
an external trigger via a newly exposed configuration
option "riscv smp_add_ext_triggers".

Original merge request:
riscv-collab#1179

Original author: Rob Bradford
rbradford@rivosinc.com
https://github.com/rbradford

Author: lz-bro

src/target/riscv/riscv-013.c

@@ -68,10 +68,6 @@ static int riscv013_access_memory(struct target *target, const riscv_mem_access_
 static bool riscv013_get_impebreak(const struct target *target);
 static unsigned int riscv013_get_progbufsize(const struct target *target);
 
-typedef enum {
-	HALT_GROUP,
-	RESUME_GROUP
-} grouptype_t;
 static int set_group(struct target *target, bool *supported, unsigned int group,
 		grouptype_t grouptype);
 
@@ -1784,6 +1780,37 @@ static void deinit_target(struct target *target)
 	info->version_specific = NULL;
 }
 
+static int smp_add_ext_trigger(struct target *target, unsigned int group,
+		riscv_ext_trigger_t external_trigger)
+{
+	uint32_t write_val = DM_DMCS2_HGSELECT;
+	assert(group <= 31);
+	assert(external_trigger.dmexttrigger < 16);
+	write_val = set_field(write_val, DM_DMCS2_GROUP, group);
+	write_val = set_field(write_val, DM_DMCS2_GROUPTYPE, external_trigger.grouptype);
+	write_val = set_field(write_val, DM_DMCS2_DMEXTTRIGGER, external_trigger.dmexttrigger);
+	if (dm_write(target, DM_DMCS2, write_val) != ERROR_OK)
+		return ERROR_FAIL;
+	write_val = set_field(write_val, DM_DMCS2_HGWRITE, 1);
+	if (dm_write(target, DM_DMCS2, write_val) != ERROR_OK)
+		return ERROR_FAIL;
+
+	uint32_t read_val;
+	if (dm_read(target, &read_val, DM_DMCS2) != ERROR_OK)
+		return ERROR_FAIL;
+	if (get_field(read_val, DM_DMCS2_GROUP) == group &&
+		get_field(read_val, DM_DMCS2_DMEXTTRIGGER) == external_trigger.dmexttrigger &&
+		get_field(read_val, DM_DMCS2_HGSELECT) == 1) {
+		LOG_TARGET_INFO(target, "External trigger %d added to %s group %d", external_trigger.dmexttrigger,
+				external_trigger.grouptype ? "resume" : "halt", group);
+	} else {
+		LOG_TARGET_ERROR(target, "External trigger %d not supported %s group %d", external_trigger.dmexttrigger,
+				external_trigger.grouptype ? "resume" : "halt", group);
+	}
+
+	return ERROR_OK;
+}
+
 static int set_group(struct target *target, bool *supported, unsigned int group,
 		grouptype_t grouptype)
 {
@@ -2153,6 +2180,20 @@ static int examine(struct target *target)
 		else
 			LOG_TARGET_INFO(target, "Core %d could not be made part of halt group %d.",
 					info->index, target->smp);
+
+		/* TODO: Resume groups with external input triggers look to be very problematic.
+		 * Neither OpenOCD nor GDB is ready for the case when a target suddenly
+		 * resumes (due to the trigger), without an explicit resume request and
+		 * at arbitrary moment in time. */
+
+		for (unsigned int i = 0; i < RISCV_MAX_EXTTRIGGERS; i++) {
+			if (r->external_triggers[i].is_set) {
+				if (smp_add_ext_trigger(target, target->smp, r->external_triggers[i]) != ERROR_OK)
+					return ERROR_FAIL;
+			} else {
+				break;
+			}
+		}
 	}
 
 	/* Some regression suites rely on seeing 'Examined RISC-V core' to know

src/target/riscv/riscv.c

@@ -5588,6 +5588,46 @@ COMMAND_HANDLER(handle_riscv_virt2phys_mode)
 	return ERROR_OK;
 }
 
+COMMAND_HANDLER(riscv_smp_add_ext_triggers)
+{
+	struct target *target = get_current_target(CMD_CTX);
+	RISCV_INFO(r);
+
+	if (CMD_ARGC % 2) {
+		LOG_ERROR("Command takes an even number of parameters.");
+		return ERROR_COMMAND_SYNTAX_ERROR;
+	}
+
+	if (CMD_ARGC > 2 * RISCV_MAX_EXTTRIGGERS) {
+		LOG_ERROR("The number of parameters can not exceeds %d.", 2 * RISCV_MAX_EXTTRIGGERS);
+		return ERROR_COMMAND_SYNTAX_ERROR;
+	}
+
+	unsigned int index = 0;
+	for (unsigned int i = 0; i < CMD_ARGC - 1; i += 2) {
+		if (!strcmp("halt_group", CMD_ARGV[i])) {
+			r->external_triggers[index].grouptype = HALT_GROUP;
+		} else if (!strcmp("resume_group", CMD_ARGV[i])) {
+			r->external_triggers[index].grouptype = RESUME_GROUP;
+		} else {
+			LOG_ERROR("%s is not a valid argument for command,"
+				"should be halt_group or resume_group.", CMD_ARGV[0]);
+			return ERROR_COMMAND_SYNTAX_ERROR;
+		}
+		int value = atoi(CMD_ARGV[i + 1]);
+		if (value <= 0 || value > 16) {
+			LOG_ERROR("%s is not a valid integer argument for command.", CMD_ARGV[i + 1]);
+			return ERROR_FAIL;
+		}
+		r->external_triggers[index].dmexttrigger = value;
+		r->external_triggers[index].is_set = true;
+		index++;
+	}
+
+	return ERROR_OK;
+}
+
+
 static const struct command_registration riscv_exec_command_handlers[] = {
 	{
 		.name = "dump_sample_buf",
@@ -5850,6 +5890,13 @@ static const struct command_registration riscv_exec_command_handlers[] = {
 			"When off, users need to take care of memory coherency themselves, for example by using "
 			"`riscv exec_progbuf` to execute fence or CMO instructions."
 	},
+	{
+		.name = "smp_add_ext_triggers",
+		.handler = riscv_smp_add_ext_triggers,
+		.mode = COMMAND_CONFIG,
+		.usage = "grouptype1 num1 [grouptype2 num2]......",
+		.help = "Add the given external triggers to the halt/resume group"
+	},
 	COMMAND_REGISTRATION_DONE
 };
 

src/target/riscv/riscv.h

@@ -144,6 +144,17 @@ typedef struct riscv_mem_access_args {
 	uint32_t increment;
 } riscv_mem_access_args_t;
 
+typedef enum {
+	HALT_GROUP,
+	RESUME_GROUP
+} grouptype_t;
+
+typedef struct {
+	grouptype_t grouptype;
+	uint32_t dmexttrigger;
+	bool is_set;
+} riscv_ext_trigger_t;
+
 static inline bool
 riscv_mem_access_is_valid(const riscv_mem_access_args_t args)
 {