fix progbuf cache: invalidate it when needed

This commit relates to progbuf cache,
implemented in https://github.com/riscv/riscv-openocd/pull/381

Make sure the cache gets invalidated when the progbuf
contents change via other means. I've identified two
such cases where the invalidation is required:

1) When the user manually tinkers with the progbuf registers
   (TCL command "riscv dmi_write")

2) When program buffer is used as a scratch memory
   (scratch_write64())

Change-Id: Ie7ffb0fccda63297de894ab919d09082ea21cfae
Signed-off-by: Jan Matyas <matyas@codasip.com>

src/target/riscv/riscv-013.c

@@ -52,6 +52,7 @@ static int riscv013_write_debug_buffer(struct target *target, unsigned index,
 		riscv_insn_t d);
 static riscv_insn_t riscv013_read_debug_buffer(struct target *target, unsigned
 		index);
+static int riscv013_invalidate_cached_debug_buffer(struct target *target);
 static int riscv013_execute_debug_buffer(struct target *target);
 static void riscv013_fill_dmi_write_u64(struct target *target, char *buf, int a, uint64_t d);
 static void riscv013_fill_dmi_read_u64(struct target *target, char *buf, int a);
@@ -1248,6 +1249,7 @@ static int scratch_write64(struct target *target, scratch_mem_t *scratch,
 		case SPACE_DMI_PROGBUF:
 			dmi_write(target, DM_PROGBUF0 + scratch->debug_address, value);
 			dmi_write(target, DM_PROGBUF1 + scratch->debug_address, value >> 32);
+			riscv013_invalidate_cached_debug_buffer(target);
 			break;
 		case SPACE_DMI_RAM:
 			{
@@ -2278,6 +2280,7 @@ static int init_target(struct command_context *cmd_ctx,
 	generic_info->read_debug_buffer = &riscv013_read_debug_buffer;
 	generic_info->write_debug_buffer = &riscv013_write_debug_buffer;
 	generic_info->execute_debug_buffer = &riscv013_execute_debug_buffer;
+	generic_info->invalidate_cached_debug_buffer = &riscv013_invalidate_cached_debug_buffer;
 	generic_info->fill_dmi_write_u64 = &riscv013_fill_dmi_write_u64;
 	generic_info->fill_dmi_read_u64 = &riscv013_fill_dmi_read_u64;
 	generic_info->fill_dmi_nop_u64 = &riscv013_fill_dmi_nop_u64;
@@ -4337,6 +4340,18 @@ riscv_insn_t riscv013_read_debug_buffer(struct target *target, unsigned index)
 	return value;
 }
 
+int riscv013_invalidate_cached_debug_buffer(struct target *target)
+{
+	dm013_info_t *dm = get_dm(target);
+	if (!dm)
+		return ERROR_FAIL;
+
+	LOG_TARGET_DEBUG(target, "Invalidating progbuf cache");
+	for (unsigned int i = 0; i < 15; i++)
+		dm->progbuf_cache[i] = 0;
+	return ERROR_OK;
+}
+
 int riscv013_execute_debug_buffer(struct target *target)
 {
 	uint32_t run_program = 0;

src/target/riscv/riscv.c

@@ -2795,11 +2795,21 @@ COMMAND_HANDLER(riscv_dmi_write)
 	COMMAND_PARSE_NUMBER(u32, CMD_ARGV[1], value);
 
 	if (r->dmi_write) {
-		return r->dmi_write(target, address, value);
+		/* Perform the DMI write */
-	} else {
+		int retval = r->dmi_write(target, address, value);
-		LOG_ERROR("dmi_write is not implemented for this target.");
+
-		return ERROR_FAIL;
+		/* If the user tinkered with progbuf registers, we need to
+		   drop our cached copy of the progbuf */
+		if (address >= DM_PROGBUF0 && address <= DM_PROGBUF15) {
+			if (r->invalidate_cached_debug_buffer)
+				r->invalidate_cached_debug_buffer(target);
+		}
+
+		return retval;
 	}
+
+	LOG_ERROR("dmi_write is not implemented for this target.");
+	return ERROR_FAIL;
 }
 
 COMMAND_HANDLER(riscv_test_sba_config_reg)

src/target/riscv/riscv.h

@@ -161,6 +161,7 @@ typedef struct {
 			riscv_insn_t d);
 	riscv_insn_t (*read_debug_buffer)(struct target *target, unsigned index);
 	int (*execute_debug_buffer)(struct target *target);
+	int (*invalidate_cached_debug_buffer)(struct target *target);
 	int (*dmi_write_u64_bits)(struct target *target);
 	void (*fill_dmi_write_u64)(struct target *target, char *buf, int a, uint64_t d);
 	void (*fill_dmi_read_u64)(struct target *target, char *buf, int a);