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

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On Thu, Apr 15, 2021 at 5:12 PM John Stultz <john.stultz@xxxxxxxxxx> wrote:
>
> On Thu, Apr 15, 2021 at 3:20 PM Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx> wrote:
> >
> > 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>
> > ---
> > Changes in v3:
> > - Check if the desired mode is OTG, then keep the old flow
> > - Remove condition for OTG support only since the device can still be
> >   configured DRD host/device mode only
> > - Remove redundant hw_mode check since __dwc3_set_mode() only applies when
> >   hw_mode is DRD
> > Changes in v2:
> > - Initialize mutex per device and not as global mutex.
> > - Add additional checks for DRD only mode
> >
>
> I've not been able to test all the different modes on HiKey960 yet,
> but with this patch we avoid the !COREIDLE hangs that we see
> frequently on bootup, so it looks pretty good to me.  I'll get back to
> you tonight when I can put hands on the board to test the gadget to
> host switching to make sure all is well (I really don't expect any
> issues, but just want to be sure).

Ok, got a chance to test the mode switching and everything is looking good.

Tested-by: John Stultz <john.stultz@xxxxxxxxxx>

Thanks again for continuing to push this!
-john



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