Re: [PATCH v3] usb: dwc3: core: Do core softreset when switch mode

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On 4/16/2021 3:47 AM, Felipe Balbi wrote:
> 
> Hi,
> 
> Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx> writes:
> 
>> From: Yu Chen <chenyu56@xxxxxxxxxx>
>> From: John Stultz <john.stultz@xxxxxxxxxx>
>>
>> According to the programming guide, to switch mode for DRD controller,
>> the driver needs to do the following.
>>
>> To switch from device to host:
>> 1. Reset controller with GCTL.CoreSoftReset
>> 2. Set GCTL.PrtCapDir(host mode)
>> 3. Reset the host with USBCMD.HCRESET
>> 4. Then follow up with the initializing host registers sequence
>>
>> To switch from host to device:
>> 1. Reset controller with GCTL.CoreSoftReset
>> 2. Set GCTL.PrtCapDir(device mode)
>> 3. Reset the device with DCTL.CSftRst
>> 4. Then follow up with the initializing registers sequence
>>
>> Currently we're missing step 1) to do GCTL.CoreSoftReset and step 3) of
>> switching from host to device. John Stult reported a lockup issue seen
>> with HiKey960 platform without these steps[1]. Similar issue is observed
>> with Ferry's testing platform[2].
>>
>> So, apply the required steps along with some fixes to Yu Chen's and John
>> Stultz's version. The main fixes to their versions are the missing wait
>> for clocks synchronization before clearing GCTL.CoreSoftReset and only
>> apply DCTL.CSftRst when switching from host to device.
>>
>> [1] https://lore.kernel.org/linux-usb/20210108015115.27920-1-john.stultz@xxxxxxxxxx/
>> [2] https://lore.kernel.org/linux-usb/0ba7a6ba-e6a7-9cd4-0695-64fc927e01f1@xxxxxxxxx/
>>
>> Cc: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
>> Cc: Ferry Toth <fntoth@xxxxxxxxx>
>> Cc: Wesley Cheng <wcheng@xxxxxxxxxxxxxx>
>> Cc: <stable@xxxxxxxxxxxxxxx>
>> Fixes: 41ce1456e1db ("usb: dwc3: core: make dwc3_set_mode() work properly")
>> Signed-off-by: Yu Chen <chenyu56@xxxxxxxxxx>
>> Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
>> Signed-off-by: Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx>
> 
> I still have concerns about the soft reset, but I won't block you guys
> from fixing Hikey's problem :-)
> 
> The only thing I would like to confirm is that this has been verified
> with hundreds of swaps happening as quickly as possible. DWC3 should
> still be functional after several hundred swaps.
> 
> Can someone confirm this is the case? (I'm assuming this can be
> scripted)
> 
Hi Thinh/Felipe,

Thanks Thinh for this change.  Will verify this on our platform as well
with a mode switch loop over the weekend.

Thanks
Wesley Cheng
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project



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