Re: [PATCH v2, 3/3] usb: dwc3: core: Workaround for CSR read timeout

[Thinh Nguyen]

On Tue, Jun 04, 2024, joswang wrote:
> On Tue, Jun 4, 2024 at 8:07 AM Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx> wrote:
> >
> > On Mon, Jun 03, 2024, joswang wrote:
> > > From: joswang <joswang@xxxxxxxxxx>
> > >
> > > DWC31 version 2.00a have an issue that would cause
> > > a CSR read timeout When CSR read coincides with RAM
> > > Clock Gating Entry.
> >
> > Do you have the STAR issue number?
> >
> Thanks for reviewing the code.
> The STAR number provided by Synopsys is 4846132.
> Please help review further.

I've confirmed internally. As you have noted, this applies to DWC_usb31
v2.00a for host mode only and DRD mode operating as host.

> 
> > >
> > > This workaround solution disable Clock Gating, sacrificing
> > > power consumption for normal operation.
> > >
> > > Signed-off-by: joswang <joswang@xxxxxxxxxx>
> > > ---
> > >  drivers/usb/dwc3/core.c | 23 +++++++++++++++++++++++
> > >  1 file changed, 23 insertions(+)
> > >
> > > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> > > index 3a8fbc2d6b99..1df85c505c9e 100644
> > > --- a/drivers/usb/dwc3/core.c
> > > +++ b/drivers/usb/dwc3/core.c
> > > @@ -978,11 +978,22 @@ static void dwc3_core_setup_global_control(struct dwc3 *dwc)
> > >                *
> > >                * STAR#9000588375: Clock Gating, SOF Issues when ref_clk-Based
> > >                * SOF/ITP Mode Used

Since there's another STAR, let's split the if-else case separately and
provide the comments separately.

> > > +              *
> > > +              * WORKAROUND: DWC31 version 2.00a have an issue that would

Can we use the full name DWC_usb31 instead of DWC31.

> > > +              * cause a CSR read timeout When CSR read coincides with RAM
> > > +              * Clock Gating Entry.
> > > +              *
> > > +              * This workaround solution disable Clock Gating, sacrificing
> > > +              * power consumption for normal operation.
> > >                */
> > >               if ((dwc->dr_mode == USB_DR_MODE_HOST ||
> > >                               dwc->dr_mode == USB_DR_MODE_OTG) &&
> > >                               DWC3_VER_IS_WITHIN(DWC3, 210A, 250A))
> > >                       reg |= DWC3_GCTL_DSBLCLKGTNG | DWC3_GCTL_SOFITPSYNC;
> > > +             else if ((dwc->dr_mode == USB_DR_MODE_HOST ||
> > > +                             dwc->dr_mode == USB_DR_MODE_OTG) &&

There's no OTG mode for DWC_usb31. Let's enable this workaround if the
HW mode is not DWC_GHWPARAMS0_MODE_GADGET.

> > > +                             DWC3_VER_IS(DWC31, 200A))
> > > +                     reg |= DWC3_GCTL_DSBLCLKGTNG;
> > >               else
> > >                       reg &= ~DWC3_GCTL_DSBLCLKGTNG;
> > >               break;
> > > @@ -992,6 +1003,18 @@ static void dwc3_core_setup_global_control(struct dwc3 *dwc)
> > >                * will work. Device-mode hibernation is not yet implemented.
> > >                */
> > >               reg |= DWC3_GCTL_GBLHIBERNATIONEN;
> > > +
> > > +             /*
> > > +              * WORKAROUND: DWC31 version 2.00a have an issue that would
> > > +              * cause a CSR read timeout When CSR read coincides with RAM
> > > +              * Clock Gating Entry.
> > > +              *
> > > +              * This workaround solution disable Clock Gating, sacrificing
> > > +              * power consumption for normal operation.
> > > +              */
> > > +             if ((dwc->dr_mode == USB_DR_MODE_HOST ||
> > > +                  dwc->dr_mode == USB_DR_MODE_OTG) && DWC3_VER_IS(DWC31, 200A))
> > > +                     reg |= DWC3_GCTL_DSBLCLKGTNG;
> > >               break;
> > >       default:
> > >               /* nothing */
> > > --
> > > 2.17.1
> > >
> >

We have the same checks and comments here. Can we refactor?
Perhaps something this?

power_opt = DWC3_GHWPARAMS1_EN_PWROPT(dwc->hwparams.hwparams1);
switch (power_opt) {
    ...
}

/*
 * <comment>
 */
if (power_opt != DWC3_GHWPARAMS1_EN_PWROPT_NO) {
}


Thanks,
Thinh