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

[Wesley Cheng]

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@xxxxxxxxxx> wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> John Stultz <john.stultz@xxxxxxxxxx> writes:
>>>>>>>> From: Yu Chen <chenyu56@xxxxxxxxxx>
>>>>>>>>
>>>>>>>> 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@xxxxxxxxxxxxxx/__;!!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@xxxxxxxxxx>
>>>>>>>> Cc: Tejas Joglekar <tejas.joglekar@xxxxxxxxxxxx>
>>>>>>>> Cc: Yang Fei <fei.yang@xxxxxxxxx>
>>>>>>>> Cc: YongQin Liu <yongqin.liu@xxxxxxxxxx>
>>>>>>>> Cc: Andrzej Pietrasiewicz <andrzej.p@xxxxxxxxxxxxx>
>>>>>>>> Cc: Thinh Nguyen <thinhn@xxxxxxxxxxxx>
>>>>>>>> Cc: Jun Li <lijun.kernel@xxxxxxxxx>
>>>>>>>> Cc: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>
>>>>>>>> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>>>>>>>> Cc: linux-usb@xxxxxxxxxxxxxxx
>>>>>>>> Signed-off-by: Yu Chen <chenyu56@xxxxxxxxxx>
>>>>>>>> Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
>>>>>>>> ---
>>>>>>>> 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@xxxxxxxxxx/__;!!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

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