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Subject: Re: [PATCH v3 1/2] usb: dwc3: Trigger a GCTL soft reset when
 switching modes in DRD
To:     John Stultz <john.stultz@linaro.org>
Cc:     Thinh Nguyen <Thinh.Nguyen@synopsys.com>,
        Felipe Balbi <balbi@kernel.org>,
        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>
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 <28bc3ce1-7ace-be25-7d7d-ca8ab1b0f0e9@synopsys.com>
 <62c7ee3a-21c4-009d-bfc0-ce9d3a84fefe@codeaurora.org>
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From:   Wesley Cheng <wcheng@codeaurora.org>
Message-ID: <d0858f04-1faa-8f4d-a8b7-e1ec9277835f@codeaurora.org>
Date:   Mon, 29 Mar 2021 19:11:22 -0700
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On 3/29/2021 3:20 PM, John Stultz wrote:
> On Mon, Mar 29, 2021 at 3:15 PM Wesley Cheng <wcheng@codeaurora.org> wrote:
>>
>>
>>
>> On 3/19/2021 4:09 PM, Thinh Nguyen wrote:
>>> Wesley Cheng wrote:
>>>>
>>>>
>>>> On 3/8/2021 10:33 PM, Wesley Cheng wrote:
>>>>>
>>>>>
>>>>> On 3/8/2021 7:05 PM, Thinh Nguyen wrote:
>>>>>> Wesley Cheng wrote:
>>>>>>>
>>>>>>> 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
>>>>>>>
>>>>>>
>>>>>> Hi Wesley,
>>>>>>
>>>>>> Actually your IP version type may use the newer flow. Can you print your
>>>>>> DWC3_VER_TYPE? I still need to verify internally to know which versions
>>>>>> need the update if any.
>>>>>>
>>>>>> Thanks,
>>>>>> Thinh
>>>>>>
>>>>> Hi Thinh,
>>>>>
>>>>> Sure, my DWC3_VER_TYPE output = 0x67612A2A
>>>>>
>>>>> Thanks
>>>>> Wesley Cheng
>>>>>
>>>> Hi Thinh,
>>>>
>>>> Would you happen to have an update on the required sequence on the
>>>> version shared?  Sorry for pushing, but we just wanted to finalize on
>>>> it, since it does cause some functional issues w/o the soft reset in
>>>> place, and causes a crash if we have the GCTL.softreset.
>>>>
>>>> Thanks
>>>> Wesley Cheng
>>>>
>>>
>>> Hi Wesley,
>>>
>>> I'm still trying to get that info for you. The versions without
>>> GCTL.softreset should be very new. The flow with GCTL.softreset should
>>> work for all versions and should not cause functional impact. We can
>>> create a change to optimize and remove GCTL.softreset for the newer
>>> controller versions at a later time.
>>>
>>> Since you and John Stultz have the setup that can be verified in the
>>> real world. It would be great if John or you provide a tested patch(es)
>>> to resolve this issue.
>>>
>>> Thanks,
>>> Thinh
>>>
>> Hi Thinh,
>>
>> Thanks for the input as always.  I tested the GCTL.softreset change just
>> now, and it is working fine at least on my set up.
>>
>> Not sure if we'd need input from other vendors as well to get this
>> change merged.
> 
> Did you test the original patch from this thread unchanged, or did you
> have any modifications? If the latter, feel free to send it out and
> I'll validate it on my side.
> 
> thanks
> -john
> 

Hi John,

I'm using your change as is.  Didn't make any modifications to it.

Thanks
Wesley Cheng

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