linux-kernel - Re: [PATCH v4 1/1] xhci: Correctly handle last TRB of isoc TD on Etron xHCI host

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Message-ID: <CAHN5xi3K3jXLZew5=4PwH8OUWeCMMcJSm5tpNgm3k1vw7LGe-g@mail.gmail.com>
Date: Mon, 10 Feb 2025 14:18:37 +0800
From: Kuangyi Chiang <ki.chiang65@...il.com>
To: Michał Pecio <michal.pecio@...il.com>
Cc: gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org, 
	linux-usb@...r.kernel.org, mathias.nyman@...el.com, stable@...r.kernel.org
Subject: Re: [PATCH v4 1/1] xhci: Correctly handle last TRB of isoc TD on
 Etron xHCI host

Michał Pecio <michal.pecio@...il.com> 於 2025年2月7日 週五 下午5:51寫道：
>
> On Fri, 7 Feb 2025 14:59:25 +0800, Kuangyi Chiang wrote:
> > >
> > > >       case COMP_STOPPED:
> > > > +             /* Think of it as the final event if TD had an error */
> > > > +             if (td->error_mid_td)
> > > > +                     td->error_mid_td = false;
> > > >               sum_trbs_for_length = true;
> > > >               break;
> > >
> > > What was the reason for this part?
> >
> > To prevent the driver from printing the following debug message twice:
> >
> > "Error mid isoc TD, wait for final completion event"
> >
> > This can happen if the driver queues a Stop Endpoint command after
> > mid isoc TD error occurred, see my debug messages below:
>
> I see. Not sure if it's a big problem, dynamic debug is disabled by
> default and anyone using it needs to read the code anyway to understand
> what those messages mean. And when you read the code it becomes obvious
> why the message can show up twice (or even more, in fact).
>
> I would even say that it is helpful, because it shows that control flow
> passes exactly as expected when the Stopped event is handled. And it's
> nothing new, this debug code always worked like that on all HCs.

Got it, thanks for your suggestion.

>
> Regards,
> Michal

Thanks,
Kuangyi Chiang