Re: [PATCH 1/2] usb: dwc2: core: add no-csftrst-wait DT property

[anis chali <chalianis1@gmail.com>]

Hello Ahmad,
Le lun. 13 avr. 2026 à 09:50, Ahmad Fatoum <a.fatoum@pengutronix.de> a écrit :
>
> Hello Anis,
>
> On 3/31/26 5:17 AM, chalianis1@gmail.com wrote:
> > From: Chali Anis <chalianis1@gmail.com>
> >
> > Some platforms (e.g. RPi4/bcm2711) do not deassert GRSTCTL_CSFTRST within
> > the expected window but continue to operate correctly, causing probe to
> > fail with ETIMEDOUT.
> >
> > Per the datasheet, GRSTCTL_CSFTRST is self-clearing but requires at least
> > 3 PHY clocks after reset before any PHY domain access. Add a 1us delay to
> > satisfy this requirement.
> >
> > Additionally introduce the 'no-csftrst-wait' devicetree property to skip
> > polling for the bit to clear on platforms where the reset completes but the
> > status bit is unreliable.
>
> I still wonder why there are no workarounds for this particular issue in
> Linux or U-Boot. We seem to do something different when we run into this
> reliably, but others don't?

I checked the initialization sequence but I didn't
find anything interesting.

> I originally thought, it may be related to the version of the IP,
> because both Linux and U-Boot have special handling for >= 4.20, but I
> checked on my Rpi4 and DWC2 has v2.80 there (Synopsis ID 4f54280a)

I implemented the u-boot logic but I had the same code with version check
and I ended by removing it since it works for now without handling the versions.

> > -     ret = dwc2_wait_bit_clear(dwc2, GRSTCTL, GRSTCTL_CSFTRST, 10000);
> > -     if (ret) {
> > -             dwc2_warn(dwc2, "%s: Timeout! Waiting for Core Soft Reset\n",
> > +     /* Wait for at least 3 PHY Clocks */
> > +     udelay(1);
> > +
> > +     if (!of_property_read_bool(np, "no-csftrst-wait")) {
>
> barebox-specific Device Tree properties should be documented in
> Documentation/devicetree/bindings/.
Okay, ack.

> Alternatively, you can check of_machine_is_compatible("brcm,bcm2711")
I choosed to add something in the device tree to not hard code a
specific machine in
dwc2 in that case we let the machine dts or users facing the same
issue to add the dts
property without even submitting patch, but if you prefer manage this
with checking the
machine compatible I can make the change???

> Cheers,
> Ahmad
>
> > +             ret = dwc2_wait_bit_clear(dwc2, GRSTCTL, GRSTCTL_CSFTRST, 10000);
> > +             if (ret) {
> > +                     dwc2_warn(dwc2, "%s: Timeout! Waiting for Core Soft Reset\n",
> >                               __func__);
> > -             return ret;
> > +                     return ret;
> > +             }
> >       }
> >
> >       if (wait_for_host_mode)
> >
> >
>
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Thank you for support.

Anis