linux-kernel - Re: [PATCH v3 1/2] usb: dwc3: Trigger a GCTL soft reset when switching modes in DRD

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Message-ID: <87bldzwr6x.fsf@kernel.org>
Date:   Fri, 08 Jan 2021 14:25:58 +0200
From:   Felipe Balbi <balbi@...nel.org>
To:     John Stultz <john.stultz@...aro.org>,
        lkml <linux-kernel@...r.kernel.org>
Cc:     Yu Chen <chenyu56@...wei.com>,
        Tejas Joglekar <tejas.joglekar@...opsys.com>,
        Yang Fei <fei.yang@...el.com>,
        YongQin Liu <yongqin.liu@...aro.org>,
        Andrzej Pietrasiewicz <andrzej.p@...labora.com>,
        Thinh Nguyen <thinhn@...opsys.com>,
        Jun Li <lijun.kernel@...il.com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, John Stultz <john.stultz@...aro.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Roger Quadros <rogerq@...com>
Subject: Re: [PATCH v3 1/2] usb: dwc3: Trigger a GCTL soft reset when
 switching modes in DRD


Hi,

John Stultz <john.stultz@...aro.org> writes:
> From: Yu Chen <chenyu56@...wei.com>
>
> Just resending this, as discussion died out a bit and I'm not
> sure how to make further progress. See here for debug data that
> was requested last time around:
>   https://lore.kernel.org/lkml/CALAqxLXdnaUfJKx0aN9xWwtfWVjMWigPpy2aqsNj56yvnbU80g@mail.gmail.com/
>
> With the current dwc3 code on the HiKey960 we often see the
> COREIDLE flag get stuck off in __dwc3_gadget_start(), which
> seems to prevent the reset irq and causes the USB gadget to
> fail to initialize.
>
> We had seen occasional initialization failures with older
> kernels but with recent 5.x era kernels it seemed to be becoming
> much more common, so I dug back through some older trees and
> realized I dropped this quirk from Yu Chen during upstreaming
> as I couldn't provide a proper rational for it and it didn't
> seem to be necessary. I now realize I was wrong.
>
> After resubmitting the quirk, Thinh Nguyen pointed out that it
> shouldn't be a quirk at all and it is actually mentioned in the
> programming guide that it should be done when switching modes
> in DRD.
>
> So, to avoid these !COREIDLE lockups seen on HiKey960, this
> patch issues GCTL soft reset when switching modes if the
> controller is in DRD mode.
>
> Cc: Felipe Balbi <balbi@...nel.org>
> Cc: Tejas Joglekar <tejas.joglekar@...opsys.com>
> Cc: Yang Fei <fei.yang@...el.com>
> Cc: YongQin Liu <yongqin.liu@...aro.org>
> Cc: Andrzej Pietrasiewicz <andrzej.p@...labora.com>
> Cc: Thinh Nguyen <thinhn@...opsys.com>
> Cc: Jun Li <lijun.kernel@...il.com>
> Cc: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: linux-usb@...r.kernel.org
> Signed-off-by: Yu Chen <chenyu56@...wei.com>
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> ---
> v2:
> * Rework to always call the GCTL soft reset in DRD mode,
>   rather then using a quirk as suggested by Thinh Nguyen
>
> v3:
> * Move GCTL soft reset under the spinlock as suggested by
>   Thinh Nguyen

Because this is such an invasive change, I would prefer that we get
Tested-By tags from a good fraction of the users before applying these
two changes.

-- 
balbi