From: Tomas Vanek <vanekt@fbl.cz>
Date: Tue, 6 Apr 2021 16:55:22 +0000 (+0200)
Subject: drivers/cmsis-dap: flush read
X-Git-Tag: v0.12.0-rc1~798
X-Git-Url: https://review.openocd.org/gitweb?p=openocd.git;a=commitdiff_plain;h=ff755a575ebf0218c2eb8745eff8050f8f02a53d;ds=sidebyside

drivers/cmsis-dap: flush read

Some CMSIS-DAP adapters keep buffered packets over
USB close/open so we need to flush up to 64 old packets
to be sure all buffers are empty.

Flush just after cmsis_dap_open() and in the case of command mismatch.

Change-Id: If21a118639e64d90635b4ecf81013d29a7b9f78d
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: http://openocd.zylin.com/6135
Tested-by: jenkins
Reviewed-by: Adrian M Negreanu <adrian.negreanu@nxp.com>
---

diff --git a/src/jtag/drivers/cmsis_dap.c b/src/jtag/drivers/cmsis_dap.c
index b5ceb6cefb..6ab0875982 100644
--- a/src/jtag/drivers/cmsis_dap.c
+++ b/src/jtag/drivers/cmsis_dap.c
@@ -281,6 +281,21 @@ static void cmsis_dap_close(struct cmsis_dap *dap)
 	}
 }
 
+static void cmsis_dap_flush_read(struct cmsis_dap *dap)
+{
+	unsigned int i;
+	/* Some CMSIS-DAP adapters keep buffered packets over
+	 * USB close/open so we need to flush up to 64 old packets
+	 * to be sure all buffers are empty */
+	for (i = 0; i < 64; i++) {
+		int retval = dap->backend->read(dap, 10);
+		if (retval == ERROR_TIMEOUT_REACHED)
+			break;
+	}
+	if (i)
+		LOG_DEBUG("Flushed %u packets", i);
+}
+
 /* Send a message and receive the reply */
 static int cmsis_dap_xfer(struct cmsis_dap *dap, int txlen)
 {
@@ -313,6 +328,8 @@ static int cmsis_dap_xfer(struct cmsis_dap *dap, int txlen)
 	if (resp[0] != current_cmd) {
 		LOG_ERROR("CMSIS-DAP command mismatch. Sent 0x%" PRIx8
 			 " received 0x%" PRIx8, current_cmd, resp[0]);
+
+		cmsis_dap_flush_read(dap);
 		return ERROR_FAIL;
 	}
 
@@ -885,6 +902,8 @@ static int cmsis_dap_init(void)
 	if (retval != ERROR_OK)
 		return retval;
 
+	cmsis_dap_flush_read(cmsis_dap_handle);
+
 	retval = cmsis_dap_get_caps_info();
 	if (retval != ERROR_OK)
 		return retval;