X-Git-Url: https://review.openocd.org/gitweb?a=blobdiff_plain;f=src%2Fjtag%2Fdrivers%2Fmpsse.c;h=41429693c15fe8a347de26cbf3e2d3a9b526e4b8;hb=30fde70c0321fd70d9330d5c6b56ed4e86653dd9;hp=063ef2ffb69bbf5fbd479105216e0e7802a72d4e;hpb=aaf5991d79fd7e620b74b3aed63e61181aa19f01;p=openocd.git

diff --git a/src/jtag/drivers/mpsse.c b/src/jtag/drivers/mpsse.c
index 063ef2ffb6..41429693c1 100644
--- a/src/jtag/drivers/mpsse.c
+++ b/src/jtag/drivers/mpsse.c
@@ -443,8 +443,8 @@ int mpsse_clock_data(struct mpsse_ctx *ctx, const uint8_t *out, unsigned out_off
 
 	while (length > 0) {
 		/* Guarantee buffer space enough for a minimum size transfer */
-		if (buffer_write_space(ctx) + (length < 8) < (out ? 4 : 3)
-		    || (in && buffer_read_space(ctx) < 1))
+		if (buffer_write_space(ctx) + (length < 8) < (out || (!out && !in) ? 4 : 3)
+				|| (in && buffer_read_space(ctx) < 1))
 			retval = mpsse_flush(ctx);
 
 		if (length < 8) {
@@ -465,8 +465,8 @@ int mpsse_clock_data(struct mpsse_ctx *ctx, const uint8_t *out, unsigned out_off
 			if (this_bytes > 65536)
 				this_bytes = 65536;
 			/* Buffer space limit. We already made sure there's space for the minimum
-			 *transfer. */
-			if (out && this_bytes + 3 > buffer_write_space(ctx))
+			 * transfer. */
+			if ((out || (!out && !in)) && this_bytes + 3 > buffer_write_space(ctx))
 				this_bytes = buffer_write_space(ctx) - 3;
 			if (in && this_bytes > buffer_read_space(ctx))
 				this_bytes = buffer_read_space(ctx);
@@ -779,11 +779,8 @@ int mpsse_flush(struct mpsse_ctx *ctx)
 	if (ctx->read_count) {
 		buffer_write_byte(ctx, 0x87); /* SEND_IMMEDIATE */
 		read_result.done = false;
-		read_transfer = libusb_alloc_transfer(0);
-		libusb_fill_bulk_transfer(read_transfer, ctx->usb_dev, ctx->in_ep, ctx->read_chunk,
-			ctx->read_chunk_size, read_cb, &read_result,
-			ctx->usb_read_timeout);
-		retval = libusb_submit_transfer(read_transfer);
+		/* delay read transaction to ensure the FTDI chip can support us with data
+		   immediately after processing the MPSSE commands in the write transaction */
 	}
 
 	struct transfer_result write_result = { .ctx = ctx, .done = false };
@@ -792,6 +789,14 @@ int mpsse_flush(struct mpsse_ctx *ctx)
 		ctx->write_count, write_cb, &write_result, ctx->usb_write_timeout);
 	retval = libusb_submit_transfer(write_transfer);
 
+	if (ctx->read_count) {
+		read_transfer = libusb_alloc_transfer(0);
+		libusb_fill_bulk_transfer(read_transfer, ctx->usb_dev, ctx->in_ep, ctx->read_chunk,
+			ctx->read_chunk_size, read_cb, &read_result,
+			ctx->usb_read_timeout);
+		retval = libusb_submit_transfer(read_transfer);
+	}
+
 	/* Polling loop, more or less taken from libftdi */
 	while (!write_result.done || !read_result.done) {
 		retval = libusb_handle_events(ctx->usb_ctx);