[PATCH] usb: dwc2: skip polling for the soft reset clear bit and add after reset delay

[chalianis1 at gmail.com]

On 2026-08-26 13:54 +0200, chalianis1 at gmail.com wrote:
> On 2026-06-29 10:56 +0000, Sascha Hauer wrote:
> > On 2026-06-23 10:23, chalianis1 wrote:
> > > From: Chali Anis <chalianis1 at gmail.com>
> > > 
> > > The RPi4 SoC do not deassert GRSTCTL_CSFTRST within the expected
> > > window but continue to operate correctly, causing probe to fail
> > > with ETIMEDOUT.
> > 
> > Does "within the expected window" imply that there is a bigger window in
> > which it is de-asserted?
> >
> What I mean is within the expected window according to the SoC datasheet
> of RK3588 which I just realized that I wrongly thought that it has a DWC2.
> Rockchip RK3588 TRM V1.0-Part2 20220309 page 2221 
> > > 
> > > 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.
> > 
> > Which datasheet, the SoC datasheet or a DWC2 datasheet?
> >
> the SOC one.
> > I'm just asking if there is a chance to not need a SoC check here.
> > 
> > Sascha
> > 
> > > 
> > > Signed-off-by: Chali Anis <chalianis1 at gmail.com>
> > > ---
> > >  drivers/usb/dwc2/core.c | 13 +++++++++----
> > >  1 file changed, 9 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/usb/dwc2/core.c b/drivers/usb/dwc2/core.c
> > > index 60cc690fdbc0..6d4b7930da9e 100644
> > > --- a/drivers/usb/dwc2/core.c
> > > +++ b/drivers/usb/dwc2/core.c
> > > @@ -809,11 +809,16 @@ int dwc2_core_reset(struct dwc2 *dwc2)
> > >  	greset |= GRSTCTL_CSFTRST;
> > >  	dwc2_writel(dwc2, greset, GRSTCTL);
> > >  
> > > -	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_machine_is_compatible("brcm,bcm2711")) {
> > > +		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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> > 
> > 
> > 
> 
> Best regards.
> Anis
> 
> 
> 
> 
I reply again on the thread because I tested something that works
by adding a delay on the the top of dwc2_core_reset the issue is
resolved and corresponds more for what the SoC even if it is not
the good datasheet stipulates see below.

diff --git a/drivers/usb/dwc2/core.c b/drivers/usb/dwc2/core.c
index 60cc690fdb..1fb8e2c6ac 100644
--- a/drivers/usb/dwc2/core.c
+++ b/drivers/usb/dwc2/core.c
@@ -776,6 +776,7 @@ int dwc2_core_reset(struct dwc2 *dwc2)
 
        dwc2_dbg(dwc2, "%s(%p)\n", __func__, dwc2);
 
+       udelay(10);
        /* Wait for AHB master IDLE state. */
        ret = dwc2_wait_bit_set(dwc2, GRSTCTL, GRSTCTL_AHBIDLE, 10000);
        if (ret) {

Best regards,
Anis