On 26.01.21 at 22:16 Andreas Hartmann wrote:

Hello Mathias!

On 26.01.21 at 18:29 Mathias Nyman wrote:

quoted

Got a first iteration ready,
any change you could try it out?

Thanks
-Mathias

8<---

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 5677b81c0915..8df30618aaf1 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c

@@ -699,11 +699,16 @@ static void xhci_unmap_td_bounce_buffer(struct xhci_hcd *xhci,
 	dma_unmap_single(dev, seg->bounce_dma, ring->bounce_buf_len,
 			 DMA_FROM_DEVICE);
 	/* for in tranfers we need to copy the data from bounce to sg */
-	len = sg_pcopy_from_buffer(urb->sg, urb->num_sgs, seg->bounce_buf,
-			     seg->bounce_len, seg->bounce_offs);
-	if (len != seg->bounce_len)
-		xhci_warn(xhci, "WARN Wrong bounce buffer read length: %zu != %d\n",
-				len, seg->bounce_len);
+	if (urb->num_sgs) {
+		len = sg_pcopy_from_buffer(urb->sg, urb->num_sgs, seg->bounce_buf,
+					   seg->bounce_len, seg->bounce_offs);
+		if (len != seg->bounce_len)
+			xhci_warn(xhci, "WARN Wrong bounce buffer read length: %zu != %d\n",
+				  len, seg->bounce_len);
+	} else {
+		memcpy(urb->transfer_buffer + seg->bounce_offs, seg->bounce_buf,
+		       seg->bounce_len);
+	}
 	seg->bounce_len = 0;
 	seg->bounce_offs = 0;
 }

@@ -3275,12 +3280,16 @@ static int xhci_align_td(struct xhci_hcd *xhci, struct urb *urb, u32 enqd_len,
 
 	/* create a max max_pkt sized bounce buffer pointed to by last trb */
 	if (usb_urb_dir_out(urb)) {
-		len = sg_pcopy_to_buffer(urb->sg, urb->num_sgs,
-				   seg->bounce_buf, new_buff_len, enqd_len);
-		if (len != new_buff_len)
-			xhci_warn(xhci,
-				"WARN Wrong bounce buffer write length: %zu != %d\n",
-				len, new_buff_len);
+		if (urb->num_sgs) {
+			len = sg_pcopy_to_buffer(urb->sg, urb->num_sgs,
+						 seg->bounce_buf, new_buff_len, enqd_len);
+			if (len != new_buff_len)
+				xhci_warn(xhci, "WARN Wrong bounce buffer write length: %zu != %d\n",
+					  len, new_buff_len);
+		} else {
+			memcpy(seg->bounce_buf, urb->transfer_buffer + enqd_len, new_buff_len);
+		}
+

If I'm understanding it correctly, you're always creating a bounce
buffer though it is not necessary (at least in my case - my test patch
proofed, that no changes at all are necessary). Why aren't you checking
for URB_NO_TRANSFER_DMA_MAP at the very beginning? Or is it your purpose
to first basically test your new code path? That would be ok.

I tested with the notebook (in both directions) - it seems to work - I
didn't get any problems though I used 24 kB bulk packets. Throughput was
unaltered high.

I'm doing the same test tomorrow with the other USB 3.1 controller!

Successfully tested on the other USB 3.1 host.

quoted

 		seg->bounce_dma = dma_map_single(dev, seg->bounce_buf,
 						 max_pkt, DMA_TO_DEVICE);
 	} else {

Thanks
Andreas