Isochronous error handling bug on VIA VL805

["Michał Pecio" <michal.pecio@gmail.com>]

I concurrently executed plan B for dealing with my NEC issues, which is
to simply order a host controller with other chip (VIA), and now I have
two controllers and three problems.

One is that it sometimes "dies" and requires a reboot, probably nothing
Linux can do about it.

The other is that it reports successful completion of the final TRB and
the driver overwrites frame->status set by prior errors. This seems to
only affect isochronous again, though I'm not 100% sure.


This change on top of yours takes care of it for transaction errors.

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index d2fe1f073e38..fce67493dfdf 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2375,6 +2375,12 @@ static int process_isoc_td(struct xhci_hcd *xhci, struct xhci_virt_ep *ep,
 	/* handle completion code */
 	switch (trb_comp_code) {
 	case COMP_SUCCESS:
+		/* Check for earlier errors; see xHCI 4.9.1 */
+		if (td->error_mid_td) {
+			xhci_info(xhci, "Got SUCCESS after mid TD error\n");
+			/* don't overwrite previously assigned status */
+			break;
+		}
 		if (remaining) {
 			frame->status = short_framestatus;
 			if (xhci->quirks & XHCI_TRUST_TX_LENGTH)


Interesting questions arise:

1. Should this be a separate patch?

2. Are there any errors that may need error_mid_td treatment on NEC?
Maybe BABBLE or others, unfortunately it isn't easy for me to produce
them and see what happens.

3. Are there any errors that may need "not success" treatment on VIA?
Any chance that these error sets aren't equal and I can't get away with
reusing your error_mid_td flag here?