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Subject: Re: [PATCH v3 1/2] usb: dwc3: Trigger a GCTL soft reset when
 switching modes in DRD
To:     Thinh Nguyen <Thinh.Nguyen@synopsys.com>,
        John Stultz <john.stultz@linaro.org>,
        Felipe Balbi <balbi@kernel.org>
Cc:     lkml <linux-kernel@vger.kernel.org>, Yu Chen <chenyu56@huawei.com>,
        Tejas Joglekar <Tejas.Joglekar@synopsys.com>,
        Yang Fei <fei.yang@intel.com>,
        YongQin Liu <yongqin.liu@linaro.org>,
        Andrzej Pietrasiewicz <andrzej.p@collabora.com>,
        Jun Li <lijun.kernel@gmail.com>,
        Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Linux USB List <linux-usb@vger.kernel.org>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        Roger Quadros <rogerq@ti.com>
References: <20210108015115.27920-1-john.stultz@linaro.org>
 <87bldzwr6x.fsf@kernel.org>
 <CALAqxLWdWj9=a-7NGDzJyrfyRABwKnJM7EQo3Zm+k9JqAhPz+g@mail.gmail.com>
 <d95d0971-624e-a0e6-ac72-6ee3b1fb1106@synopsys.com>
 <06a44245-4f2f-69ba-fe46-b88a19f585c2@codeaurora.org>
 <a33f7c33-f95d-60c3-70f2-4b37fcf8bac5@synopsys.com>
From:   Wesley Cheng <wcheng@codeaurora.org>
Message-ID: <fa5cc67e-3873-e6d9-8727-d160740b027e@codeaurora.org>
Date:   Sun, 7 Mar 2021 12:04:47 -0800
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On 3/6/2021 3:41 PM, Thinh Nguyen wrote:
> 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@kernel.org> wrote:
>>>>> Hi,
>>>>>
>>>>> John Stultz <john.stultz@linaro.org> writes:
>>>>>> From: Yu Chen <chenyu56@huawei.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@kernel.org>
>>>>>> Cc: Tejas Joglekar <tejas.joglekar@synopsys.com>
>>>>>> Cc: Yang Fei <fei.yang@intel.com>
>>>>>> Cc: YongQin Liu <yongqin.liu@linaro.org>
>>>>>> Cc: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
>>>>>> Cc: Thinh Nguyen <thinhn@synopsys.com>
>>>>>> Cc: Jun Li <lijun.kernel@gmail.com>
>>>>>> Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
>>>>>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>>>>> Cc: linux-usb@vger.kernel.org
>>>>>> Signed-off-by: Yu Chen <chenyu56@huawei.com>
>>>>>> Signed-off-by: John Stultz <john.stultz@linaro.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.
> 
Hi Thinh,

Hmmm, can you help check the register description for the PRTCAPDIR on
your v1.90a databook?  (Table 1-19 Fields for Register: GCTL (Continued)
Pg73)  When we compared the sequence in the description there to the
previous versions it removed the GCTL.softreset.  If it still shows up
on yours, then maybe my v1.90a isn't the final version?

Thanks
Wesley Cheng

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