Re: [PATCH] usb: dwc3: Toggle GCTL.CORESOFTRESET as a first step

[Andrey Smirnov <andrew.smirnov@gmail.com>]

On Mon, Mar 11, 2019 at 12:13 AM Sascha Hauer <s.hauer@pengutronix.de> wrote:
>
> On Wed, Mar 06, 2019 at 11:48:13PM -0800, Andrey Smirnov wrote:
> > Toggle GCTL.CORESOFTRESET before trying to access any of the block's
> > registers. Without this additional step, first read of DWC3_GHWPARAMS*
> > that follows results in assertion of GSTS.CSRTIMEOUT and IP block
> > stuck in a non-functional state.
> >
> > Note that all above has only been observed on i.MX8MQ (ZII Zest board)
> > for USB1 controller. USB2 doesn't seem to be affected by this.
> >
> > Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
> > ---
> >  drivers/usb/dwc3/core.c | 17 +++++++++++++++++
> >  1 file changed, 17 insertions(+)
> >
> > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> > index 2e7031a34..1fc24a441 100644
> > --- a/drivers/usb/dwc3/core.c
> > +++ b/drivers/usb/dwc3/core.c
> > @@ -663,6 +663,21 @@ static void dwc3_check_params(struct dwc3 *dwc)
> >       }
> >  }
> >
> > +static void dwc3_coresoft_reset(struct dwc3 *dwc)
> > +{
> > +     u32 reg;
> > +
> > +     reg = dwc3_readl(dwc->regs, DWC3_GCTL);
> > +     reg |= DWC3_GCTL_CORESOFTRESET;
> > +     dwc3_writel(dwc->regs, DWC3_GCTL, reg);
> > +
> > +     mdelay(100);
>
> 100ms is quite long. Isn't a shorter delay enough?

Hmm, not sure, that's the number I got from similar reset sequence
found in U-Boot. I'll experiment on bringing it down and submit a v2
if smaller delay is enough.

Thanks,
Andrey Smirnov

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