drivers/bitbang: add support for SWD multidrop

Ignore ack received after DP_TARGETSEL write to prevent false error.

This change also fixes a bug:
Received ACK FAULT or JUNK value were incorrectly stored to queued_retval
and later used as bitbang_swd_run_queue() error return.

Use LOG_ERROR for parity mismatch.

Change-Id: I5ff1f658f221af78d8bbec8416a7a0fc64ba2550
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: https://review.openocd.org/c/openocd/+/6700
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

1 files changed, 33 insertions, 42 deletions

diff --git a/src/jtag/drivers/bitbang.c b/src/jtag/drivers/bitbang.c
index d202a05..898d6d3 100644
--- a/src/jtag/drivers/bitbang.c
+++ b/src/jtag/drivers/bitbang.c
@@ -492,38 +492,30 @@ static void bitbang_swd_read_reg(uint8_t cmd, uint32_t *value, uint32_t ap_delay
 		uint32_t data = buf_get_u32(trn_ack_data_parity_trn, 1 + 3, 32);
 		int parity = buf_get_u32(trn_ack_data_parity_trn, 1 + 3 + 32, 1);
 
-		LOG_DEBUG("%s %s %s reg %X = %08"PRIx32,
+		LOG_DEBUG("%s %s read reg %X = %08"PRIx32,
 			  ack == SWD_ACK_OK ? "OK" : ack == SWD_ACK_WAIT ? "WAIT" : ack == SWD_ACK_FAULT ? "FAULT" : "JUNK",
 			  cmd & SWD_CMD_APNDP ? "AP" : "DP",
-			  cmd & SWD_CMD_RNW ? "read" : "write",
 			  (cmd & SWD_CMD_A32) >> 1,
 			  data);
 
-		switch (ack) {
-		 case SWD_ACK_OK:
-			if (parity != parity_u32(data)) {
-				LOG_DEBUG("Wrong parity detected");
-				queued_retval = ERROR_FAIL;
-				return;
-			}
-			if (value)
-				*value = data;
-			if (cmd & SWD_CMD_APNDP)
-				bitbang_swd_exchange(true, NULL, 0, ap_delay_clk);
-			return;
-		 case SWD_ACK_WAIT:
-			LOG_DEBUG("SWD_ACK_WAIT");
+		if (ack == SWD_ACK_WAIT) {
 			swd_clear_sticky_errors();
-			break;
-		 case SWD_ACK_FAULT:
-			LOG_DEBUG("SWD_ACK_FAULT");
-			queued_retval = ack;
+			continue;
+		} else if (ack != SWD_ACK_OK) {
+			queued_retval = swd_ack_to_error_code(ack);
 			return;
-		 default:
-			LOG_DEBUG("No valid acknowledge: ack=%d", ack);
-			queued_retval = ack;
+		}
+
+		if (parity != parity_u32(data)) {
+			LOG_ERROR("Wrong parity detected");
+			queued_retval = ERROR_FAIL;
 			return;
 		}
+		if (value)
+			*value = data;
+		if (cmd & SWD_CMD_APNDP)
+			bitbang_swd_exchange(true, NULL, 0, ap_delay_clk);
+		return;
 	}
 }
 
@@ -537,6 +529,9 @@ static void bitbang_swd_write_reg(uint8_t cmd, uint32_t value, uint32_t ap_delay
 		return;
 	}
 
+	/* Devices do not reply to DP_TARGETSEL write cmd, ignore received ack */
+	bool check_ack = swd_cmd_returns_ack(cmd);
+
 	for (;;) {
 		uint8_t trn_ack_data_parity_trn[DIV_ROUND_UP(4 + 3 + 32 + 1 + 4, 8)];
 		buf_set_u32(trn_ack_data_parity_trn, 1 + 3 + 1, 32, value);
@@ -551,31 +546,27 @@ static void bitbang_swd_write_reg(uint8_t cmd, uint32_t value, uint32_t ap_delay
 		bitbang_swd_exchange(false, trn_ack_data_parity_trn, 1 + 3 + 1, 32 + 1);
 
 		int ack = buf_get_u32(trn_ack_data_parity_trn, 1, 3);
-		LOG_DEBUG("%s %s %s reg %X = %08"PRIx32,
+
+		LOG_DEBUG("%s%s %s write reg %X = %08"PRIx32,
+			  check_ack ? "" : "ack ignored ",
 			  ack == SWD_ACK_OK ? "OK" : ack == SWD_ACK_WAIT ? "WAIT" : ack == SWD_ACK_FAULT ? "FAULT" : "JUNK",
 			  cmd & SWD_CMD_APNDP ? "AP" : "DP",
-			  cmd & SWD_CMD_RNW ? "read" : "write",
 			  (cmd & SWD_CMD_A32) >> 1,
 			  buf_get_u32(trn_ack_data_parity_trn, 1 + 3 + 1, 32));
 
-		switch (ack) {
-		 case SWD_ACK_OK:
-			if (cmd & SWD_CMD_APNDP)
-				bitbang_swd_exchange(true, NULL, 0, ap_delay_clk);
-			return;
-		 case SWD_ACK_WAIT:
-			LOG_DEBUG("SWD_ACK_WAIT");
-			swd_clear_sticky_errors();
-			break;
-		 case SWD_ACK_FAULT:
-			LOG_DEBUG("SWD_ACK_FAULT");
-			queued_retval = ack;
-			return;
-		 default:
-			LOG_DEBUG("No valid acknowledge: ack=%d", ack);
-			queued_retval = ack;
-			return;
+		if (check_ack) {
+			if (ack == SWD_ACK_WAIT) {
+				swd_clear_sticky_errors();
+				continue;
+			} else if (ack != SWD_ACK_OK) {
+				queued_retval = swd_ack_to_error_code(ack);
+				return;
+			}
 		}
+
+		if (cmd & SWD_CMD_APNDP)
+			bitbang_swd_exchange(true, NULL, 0, ap_delay_clk);
+		return;
 	}
 }