Re: [PATCH v3 2/2] usb: dwc3: core: defer probe on ulpi_read_id timeout

[Ferry Toth]

On 18-11-2022 03:11, Thinh Nguyen wrote:
> On Thu, Nov 17, 2022, Ferry Toth wrote:
> > Since commit 0f010171
> I don't your update as noted in the v3 change (ie. Greg's suggestions).

Indeed. I seem to have sent in the wrong sha. Sorry about this.

> > Dual Role support on Intel Merrifield platform broke due to rearranging
> > the call to dwc3_get_extcon().
> >
> > It appears to be caused by ulpi_read_id() masking the timeout on the first
> > test write. In the past dwc3 probe continued by calling dwc3_core_soft_reset()
> > followed by dwc3_get_extcon() which happend to return -EPROBE_DEFER.
> > On deferred probe ulpi_read_id() finally succeeded.
> >
> > As we now changed ulpi_read_id() to return -ETIMEDOUT in this case, we
> > need to handle the error by calling dwc3_core_soft_reset() and request
> > -EPROBE_DEFER. On deferred probe ulpi_read_id() is retried and succeeds.
> >
> > Signed-off-by: Ferry Toth <ftoth@xxxxxxxxxxxxxx>
> > ---
> >   drivers/usb/dwc3/core.c | 7 ++++++-
> >   1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> > index 648f1c570021..2779f17bffaf 100644
> > --- a/drivers/usb/dwc3/core.c
> > +++ b/drivers/usb/dwc3/core.c
> > @@ -1106,8 +1106,13 @@ static int dwc3_core_init(struct dwc3 *dwc)
> >   
> >   	if (!dwc->ulpi_ready) {
> >   		ret = dwc3_core_ulpi_init(dwc);
> > -		if (ret)
> > +		if (ret) {
> > +			if (ret == -ETIMEDOUT) {
> > +				dwc3_core_soft_reset(dwc);
> I'm not sure if you saw my previous response. I wanted to check to see
> if we need to do soft-reset once before ulpi init as part of its
> initialization.
I missed it but found it now. I will try your suggestion and answer.
> I'm just curious why Andrey Smirnov test doesn't require this change. If
> it's a quirk for this specific configuration, then the change here is
> fine. If it's required for all ULPI setup, then we can unconditionally
> do that for all ULPI setup during initialization.

Yes me too. I can reproduce that when I build kernel and rootfs with 
buildroot there is no issue. But as soon as I add ftrace / bootconfig 
the issue appears and then I can't analyze the flow. It's seems some 
kind of timing / race.

However, I have tried deferring without dwc3_core_soft_reset() (to 
verify if it is just a matter of time) and that doesn't work. dwc3 is 
deferred about 10x and then gives up without phy. So, it's not just the 
time and not just a matter of retrying the test write.

> > +				ret = -EPROBE_DEFER;
> > +			}
> >   			goto err0;
> > +		}
> >   		dwc->ulpi_ready = true;
> >   	}
> >   
> > --
> > 2.37.2
> Thanks,
> Thinh