Re: [Regression] usb: xhci: Add XHCI_TRUST_TX_LENGTH for Renesas uPD720201

From: Daniel Thompson
Date: Tue Aug 14 2018 - 09:28:04 EST

On Fri, Aug 10, 2018 at 12:13:53PM -0400, Joseph Salisbury wrote:
> Hi Daniel,
> A kernel bug report was opened against Ubuntu [0].  It was found the
> following patch introduced the regression:
> da9970668948 ("usb: xhci: Add XHCI_TRUST_TX_LENGTH for Renesas uPD720201")

I can see nothing in that indicates a regression
in this patch. How could there be? The patch does not not alter the
behaviour of uPD720202 devices (pdev->device == 0x0015).

> The bug reporter claims there is a typo in the patch that caused the
> regression.  I built a test kernel with a change to the suspected typo
> and the bug reporter claims it resolved the regression.  My test kernel
> had the following change:
> -                       pdev->device == 0x0014)
> +                       pdev->device == 0x0015)
> I was hoping to get your feedback, since you are the patch author.  Do
> you think this is an actual typo, or maybe there really needs to be two
> quirks?

No, it is a not a typo (and the change above *does* introduce a regression
;-) ). From this git logs I believe that:

0x0014 -> uPD720201
0x0015 -> uPD720202