Flush register cache when disconnecting or polling (#656)

This makes things work as expected when OpenOCD disconnects and then
connects again. (This became a problem in #645, which started using the
cache.)

Change-Id: I764e5b410a1a68ca47d2ec39968085618ee363c2
Signed-off-by: Tim Newsome <tim@sifive.com>

src/target/riscv/riscv.c

@@ -489,6 +489,9 @@ static void riscv_deinit_target(struct target *target)
 	riscv_info_t *info = (riscv_info_t *) target->arch_info;
 	struct target_type *tt = get_target_type(target);
 
+	if (riscv_flush_registers(target) != ERROR_OK)
+		LOG_ERROR("[%s] Failed to flush registers. Ignoring this error.", target_name(target));
+
 	if (tt && info->version_specific)
 		tt->deinit_target(target);
 
@@ -2085,6 +2088,14 @@ static enum riscv_poll_hart riscv_poll_hart(struct target *target, int hartid)
 	/* If OpenOCD thinks we're running but this hart is halted then it's time
 	 * to raise an event. */
 	bool halted = riscv_is_halted(target);
+
+	if (halted && timeval_ms() - r->last_activity > 100) {
+		/* If we've been idle for a while, flush the register cache. Just in case
+		 * OpenOCD is going to be disconnected without shutting down cleanly. */
+		if (riscv_flush_registers(target) != ERROR_OK)
+			return ERROR_FAIL;
+	}
+
 	if (target->state != TARGET_HALTED && halted) {
 		LOG_DEBUG("  triggered a halt");
 		r->on_halt(target);
@@ -3646,6 +3657,7 @@ int riscv_get_register(struct target *target, riscv_reg_t *value,
 
 int riscv_save_register(struct target *target, enum gdb_regno regid)
 {
+	RISCV_INFO(r);
 	riscv_reg_t value;
 	if (!target->reg_cache) {
 		assert(!target_was_examined(target));
@@ -3663,6 +3675,9 @@ int riscv_save_register(struct target *target, enum gdb_regno regid)
 	 * because the caller is about to mess with the underlying value of the
 	 * register. */
 	reg->dirty = true;
+
+	r->last_activity = timeval_ms();
+
 	return ERROR_OK;
 }
 

src/target/riscv/riscv.h

@@ -232,6 +232,9 @@ typedef struct {
 
 	riscv_sample_config_t sample_config;
 	riscv_sample_buf_t sample_buf;
+
+	/* Track when we were last asked to do something substantial. */
+	int64_t last_activity;
 } riscv_info_t;
 
 COMMAND_HELPER(riscv_print_info_line, const char *section, const char *key,