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 BR, Thinh
