On 20.5.2021 23.30, Thinh Nguyen wrote:

+Mathias

...

Hm... looks like we have a couple of issues in the uas storage class
driver and the xhci driver.

We may need to fix that in the uas storage driver because it doesn't
seem to handle it. (check uas_data_cmplt() in uas.c).

As for the xhci driver, there maybe a case where the stream URB never
gets to complete because the transaction err_count is not properly
updated. The err_count for transaction error is stored in ep_ring, but
the xhci driver may not be able to lookup the correct ep_ring based on
TRB address for streams. There are cases for streams where the event
TRBs have their TRB pointer field cleared to '0' (xhci spec section
4.12.2). If the xhci driver doesn't see ep_ring for transaction error,
it automatically does a soft-retry. This is seen from one of our
testings that the driver was repeatedly doing soft-retry until the class
driver timed out.

Hi Mathias, maybe you have some comment on this? Thanks.

This is true, if TRB pointer is 0 then there is no retry limit for soft retry.
We should add one and prevent a loop. after e few soft resets we can end with a
hard reset to clear the host side endpoint halt.

We don't know the URB that was being tansferred during the error, and can't 
give it back with a proper error code.
In that sense we still end up waiting for a timeout and someone to cancel
the urb.

-Mathias