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

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On Fri, Apr 16, 2021 at 12:49 PM Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx> wrote:
>
> John Stultz wrote:
> > On Fri, Apr 16, 2021 at 3:47 AM Felipe Balbi <balbi@xxxxxxxxxx> 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://urldefense.com/v3/__https://lore.kernel.org/linux-usb/20210108015115.27920-1-john.stultz@xxxxxxxxxx/__;!!A4F2R9G_pg!L4TLb25Nkq0DF2qrCPWW13PUq4idhDn5QSZhgvnVAy7wJiYFOSSouSptwo9nOzIdPD4j$
> >>> [2] https://urldefense.com/v3/__https://lore.kernel.org/linux-usb/0ba7a6ba-e6a7-9cd4-0695-64fc927e01f1@xxxxxxxxx/__;!!A4F2R9G_pg!L4TLb25Nkq0DF2qrCPWW13PUq4idhDn5QSZhgvnVAy7wJiYFOSSouSptwo9nO21VT8q7$
> >>>
> >>> 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)
> >
> > I unfortunately don't have an easy way to automate the switching right
> > off. But I'll try to hack up the mux switch driver to provide an
> > interface we can script against.
> >
>
> FYI, you can do the following:
>
> 1) Enable "usb-role-switch" DT property if not already done so
> 2) Add userspace control:
>
> diff --git a/drivers/usb/dwc3/drd.c b/drivers/usb/dwc3/drd.c
> index e2b68bb770d1..b203e3d87291 100644
> --- a/drivers/usb/dwc3/drd.c
> +++ b/drivers/usb/dwc3/drd.c
> @@ -555,6 +555,7 @@ static int dwc3_setup_role_switch(struct dwc3 *dwc)
>                 mode = DWC3_GCTL_PRTCAP_DEVICE;
>         }
>
> +       dwc3_role_switch.allow_userspace_control = true;
>         dwc3_role_switch.fwnode = dev_fwnode(dwc->dev);
>         dwc3_role_switch.set = dwc3_usb_role_switch_set;
>         dwc3_role_switch.get = dwc3_usb_role_switch_get;
>
> 3) Write a script to do the following:
>
> # echo host > /sys/class/usb_role/<UDC>/role
>
> and
>
> # echo device > /sys/class/usb_role/<UDC>/role

Thanks so much for this. So I ran both of those commands in a while
loop for awhile and didn't see any trouble.

HiKey960 is interesting as well because we have a mux switch, which is
sort of an intermediary roll switcher (it gets the role switch signal
from the tcpci_rt1711h, tweaks some gpios and then signals the dwc3).
So I also did the above tweaks to the mux-switch and had it switching
between device/none and validated the onboard hub came up and down
along with the dwc3 core.

Everything still looks good here.

thanks
-john

thanks
-john



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