Re: [PATCH 1/2] usb: dwc2: handle NAK when CHHLTD does not fire

anis chali
2026-04-20T15:40:49Z

Hi, Okay I will give it a try today and come back to you.

Anis C.

Le lun. 20 avr. 2026 à 10:11, Ahmad Fatoum <a.fatoum@pengutronix.de> a écrit :
>
> Hi,
>
> fixing the Cc.
>
> On 4/20/26 2:18 PM, Sascha Hauer wrote:
> > +Cc Chali Anis <chalianis1@gmail.com>
> >
> > On Mon, Apr 20, 2026 at 01:32:25PM +0200, Ahmad Fatoum wrote:
> >> Hello,
> >>
> >> On 4/20/26 1:20 PM, Sascha Hauer wrote:
> >>> From: Sascha Hauer <sascha@saschahauer.de>
> >>>
> >>> Some DWC2 configurations do not assert CHHLTD when a NAK is received;
> >>> the hardware keeps the channel active and only sets the NAK bit in HCINT.
> >>> wait_for_chhltd() polls for CHHLTD with a 10ms timeout; when CHHLTD never
> >>> fires the timeout expires and -ETIMEDOUT is returned without inspecting
> >>> HCINT. This causes the caller to treat the NAK as a hard error instead of
> >>> a retryable condition.
> >>>
> >>> The symptom is that devices which NAK bulk or control transfers during
> >>> initialisation (e.g. some Samsung USB-C flash drives that NAK while their
> >>> firmware starts up) fail immediately rather than being retried via the
> >>> 5-second NAK-retry loop in dwc2_submit_bulk_msg() or the do/while loops
> >>> in dwc2_submit_control_msg().
> >>>
> >>> Fix by reading HCINT before aborting the channel when the CHHLTD timeout
> >>> fires. If the NAK or FRMOVRUN bit is set, abort the channel, wait for the
> >>> abort to complete, and return -EAGAIN so that the existing retry logic can
> >>> handle the NAK. Log a diagnostic message if the channel abort itself times
> >>> out, which would indicate a real hardware problem.
> >>
> >> How does this relate to
> >> https://lore.barebox.org/barebox/20260331034819.227094-1-chalianis1@gmail.com/
> >>
> >> Do we need both? Only this one? Is there something over there, which you
> >> would want in your series?
> >
> > Sounds related, but seems to be a different issue. It says "handle the case where
> > DMA has already completed by the time we get here". DMA is not an issue
> > in my case. We likely need a combination of both, but Chali, could you
> > give my patch without yours a try to see if it changes something for
> > good in your case?
> >
> > Sascha
> >
>
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