X-Git-Url: https://review.openocd.org/gitweb?p=openocd.git;a=blobdiff_plain;f=src%2Fjtag%2Fdrivers%2Fkitprog.c;h=522eb17bb735e35fbd6c925ce7cf5b9eff3b2363;hp=db5b62e2e56efe8f9eb52009b8aa0067dcf75e59;hb=7829bb701f1d9b294c627142911529ca34a1120b;hpb=a28dea0fe429339e4f8d356fbff19cb17350c9ca

diff --git a/src/jtag/drivers/kitprog.c b/src/jtag/drivers/kitprog.c
index db5b62e2e5..522eb17bb7 100644
--- a/src/jtag/drivers/kitprog.c
+++ b/src/jtag/drivers/kitprog.c
@@ -741,12 +741,22 @@ static int kitprog_swd_run_queue(void)
 			break;
 		}
 
-		/* We use the maximum buffer size here because the KitProg sometimes
-		 * doesn't like bulk reads of fewer than 62 bytes. (?!?!)
+		/* KitProg firmware does not send a zero length packet
+		 * after the bulk-in transmission of a length divisible by bulk packet
+		 * size (64 bytes) as required by the USB specification.
+		 * Therefore libusb would wait for continuation of transmission.
+		 * Workaround: Limit bulk read size to expected number of bytes
+		 * for problematic tranfer sizes. Otherwise use the maximum buffer
+		 * size here because the KitProg sometimes doesn't like bulk reads
+		 * of fewer than 62 bytes. (?!?!)
 		 */
+		size_t read_count_workaround = SWD_MAX_BUFFER_LENGTH;
+		if (read_count % 64 == 0)
+			read_count_workaround = read_count;
+
 		ret = jtag_libusb_bulk_read(kitprog_handle->usb_handle,
 				BULK_EP_IN | LIBUSB_ENDPOINT_IN, (char *)buffer,
-				SWD_MAX_BUFFER_LENGTH, 0);
+				read_count_workaround, 1000);
 		if (ret > 0) {
 			/* Handle garbage data by offsetting the initial read index */
 			if ((unsigned int)ret > read_count)