On Wed, Oct 21, 2020 at 12:14 PM Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx> wrote: > > John Stultz wrote: > > From: Yu Chen <chenyu56@xxxxxxxxxx> > > > > 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. > > > > On the upside, I can now understand more why such a quirk is > > needed. > > This shouldn't be a quirk. It's part of the programming guide when > switching mode in DRD. I don't know how we missed this. Ah! That's great, as it should simplify the patch a bit and avoid introducing another dt bindings! > > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c > > index bdf0925da6b6..b138c67e3892 100644 > > --- a/drivers/usb/dwc3/core.c > > +++ b/drivers/usb/dwc3/core.c > > @@ -114,6 +114,19 @@ void dwc3_set_prtcap(struct dwc3 *dwc, u32 mode) > > dwc->current_dr_role = mode; > > } > > > > +static void dwc3_gctl_core_soft_reset(struct dwc3 *dwc) > > +{ > > + int reg; > > + > > + reg = dwc3_readl(dwc->regs, DWC3_GCTL); > > + reg |= (DWC3_GCTL_CORESOFTRESET); > > + dwc3_writel(dwc->regs, DWC3_GCTL, reg); > > + > > + reg = dwc3_readl(dwc->regs, DWC3_GCTL); > > + reg &= ~(DWC3_GCTL_CORESOFTRESET); > > + dwc3_writel(dwc->regs, DWC3_GCTL, reg); > > +} > > + > > static void __dwc3_set_mode(struct work_struct *work) > > { > > struct dwc3 *dwc = work_to_dwc(work); > > @@ -178,6 +191,10 @@ static void __dwc3_set_mode(struct work_struct *work) > > } > > break; > > case DWC3_GCTL_PRTCAP_DEVICE: > > + /* Execute a GCTL Core Soft Reset when switch mode */ > > + if (dwc->gctl_reset_quirk) > > + dwc3_gctl_core_soft_reset(dwc); > > + > > This should be done before dwc3_set_prtcap(), and this applies when > switching from device to host mode also. Make sure to check if the > controller is DRD before doing this. Sorry, by checking that the controller is DRD, I'm not sure exactly what you mean. Checking DWC3_GHWPARAMS0_MODE_DRD? Or something else? Thanks so much for the review and feedback! -john