Re: [PATCH] xhci: handle isoc Babble and Buffer Overrun events properly

[Mathias Nyman <mathias.nyman@linux.intel.com>]

On 23.1.2024 11.10, Michal Pecio wrote:
> xHCI 4.9 explicitly forbids assuming that the xHC has released its
> ownership of a multi-TRB TD when it reports an error on one of the
> early TRBs. Yet the driver makes such assumption and releases the TD,
> allowing the remaining TRBs to be freed or overwritten by new TDs.
> 
> The xHC should also report completion of the final TRB due to its IOC
> flag being set by us, regardless of prior errors. This event cannot
> be recognized if the TD has already been freed earlier, resulting in
> "Transfer event TRB DMA ptr not part of current TD" error message.
> 
> Fix this by reusing the logic for processing isoc Transaction Errors.
> This also handles hosts which fail to report the final completion.
> 
> Fix transfer length reporting on Babble errors. They may be caused by
> device malfunction, no guarantee that the buffer has been filled.
> 
> Signed-off-by: Michal Pecio <michal.pecio@gmail.com>

Thanks, adding to queue.

> ---
> 
> Question:
> 
> Will this become a game of whack-a-mole as new cases are reported?
> 
> Would it make sense to apply error_mid_td right away to more codes
> that plausibly lead to an abort of the current TD?
> 
> Or do it after the initial patches prove themselves in real world?

I'd send tested patches that solve real world issues first to the usb-linus
(6.8 kernel), with stable tags.

Then sort out if we need to add error_mid_td to other completion codes,
and send patches for those to usb-next (6.9 kernel)

-Mathias