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

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Date:   Sat, 6 Mar 2021 23:41:27 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Wesley Cheng <wcheng@...eaurora.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        John Stultz <john.stultz@...aro.org>,
        Felipe Balbi <balbi@...nel.org>
CC:     lkml <linux-kernel@...r.kernel.org>, 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>,
        Jun Li <lijun.kernel@...il.com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux USB List <linux-usb@...r.kernel.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

Wesley Cheng wrote:
>
> On 1/8/2021 4:44 PM, Thinh Nguyen wrote:
>> Hi,
>>
>> John Stultz wrote:
>>> On Fri, Jan 8, 2021 at 4:26 AM Felipe Balbi <balbi@...nel.org> wrote:
>>>> 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://urldefense.com/v3/__https://lore.kernel.org/lkml/CALAqxLXdnaUfJKx0aN9xWwtfWVjMWigPpy2aqsNj56yvnbU80g@mail.gmail.com/__;!!A4F2R9G_pg!LNzuprAeg-O80SgolYkIkW4-ne-M-yLWCDUY9MygAIrQC398Z6gRJ9wnsnlqd3w$ 
>>>>>
>>>>> 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.
>>> I'm happy to reach out to folks to try to get that. Though I'm
>>> wondering if it would be better to put it behind a dts quirk flag, as
>>> originally proposed?
>>>    https://urldefense.com/v3/__https://lore.kernel.org/lkml/20201021181803.79650-1-john.stultz@linaro.org/__;!!A4F2R9G_pg!LNzuprAeg-O80SgolYkIkW4-ne-M-yLWCDUY9MygAIrQC398Z6gRJ9wnRWITZfc$ 
>>>
>>> That way folks can enable it for devices as they need?
>>>
>>> Again, I'm not trying to force this in as-is, just mostly sending it
>>> out again for discussion to understand what other approach might work.
>>>
>>> thanks
>>> -john
>> A quirk would imply something is broken/diverged from the design right?
>> But it's not the case here, and at least this is needed for HiKey960.
>> Also, I think Rob will be ok with not adding 1 more quirk to the dwc3
>> devicetree. :)
>>
>> BR,
>> Thinh
>>
> Hi All,
>
> Sorry for jumping in, but I checked the SNPS v1.90a databook, and that
> seemed to remove the requirement for the GCTL.softreset before writing
> to PRTCAPDIR.  Should we consider adding a controller version/IP check?
>

Hi Wesley,

From what I see in the v1.90a databook and others, the flow remains the
same. I need to check internally, but I'm not aware of the change.

BR,
Thinh