Re: [PATCH v1 1/1] usb: ulpi: defer ulpi_register on ulpi_read_id timeout

[Ferry Toth]

(sorry sent html with previous attempt)

On 10-11-2022 01:06, Thinh Nguyen wrote:
> Hi Ferry,
>
> On Wed, Nov 09, 2022, Ferry Toth wrote:
> > Since commit 0f010171
> > 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() on the first test write failing
> > with -ETIMEDOUT. Currently ulpi_read_id() expects to discover the phy via
> > DT when the test write fails and returns 0 in that case even if DT does not
> > provide the phy. Due to the timeout being masked dwc3 probe continues by
> > calling dwc3_core_soft_reset() followed by dwc3_get_extcon() which happens
> > to return -EPROBE_DEFER. On deferred probe ulpi_read_id() finally succeeds.
> >
> > This patch changes ulpi_read_id() to return -ETIMEDOUT when it occurs and
> > catches the error in dwc3_core_init(). It handles the error by calling
> > dwc3_core_soft_reset() after which it requests -EPROBE_DEFER. On deferred
> > probe ulpi_read_id() again succeeds.
> >
> > Signed-off-by: Ferry Toth<ftoth@xxxxxxxxxxxxxx>
> > ---
> >   drivers/usb/common/ulpi.c | 5 +++--
> >   drivers/usb/dwc3/core.c   | 5 ++++-
> >   2 files changed, 7 insertions(+), 3 deletions(-)
> Can you split the dwc3 change and ulpi change to separate patches?

Thanks for your comments.

I will send v2

> > diff --git a/drivers/usb/common/ulpi.c b/drivers/usb/common/ulpi.c
> > index d7c8461976ce..d8f22bc2f9d0 100644
> > --- a/drivers/usb/common/ulpi.c
> > +++ b/drivers/usb/common/ulpi.c
> > @@ -206,8 +206,9 @@ static int ulpi_read_id(struct ulpi *ulpi)
> >   
> >   	/* Test the interface */
> >   	ret = ulpi_write(ulpi, ULPI_SCRATCH, 0xaa);
> > -	if (ret < 0)
> > -		goto err;
> > +	if (ret < 0) {
> > +		return ret;
> > +	}
> >   
> >   	ret = ulpi_read(ulpi, ULPI_SCRATCH);
> >   	if (ret < 0)
> > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> > index 648f1c570021..e293ef70039b 100644
> > --- a/drivers/usb/dwc3/core.c
> > +++ b/drivers/usb/dwc3/core.c
> > @@ -1106,8 +1106,11 @@ static int dwc3_core_init(struct dwc3 *dwc)
> >   
> >   	if (!dwc->ulpi_ready) {
> >   		ret = dwc3_core_ulpi_init(dwc);
> > -		if (ret)
> > +		if (ret) {
> > +			dwc3_core_soft_reset(dwc);
> We shouldn't need to do soft reset here. The controller shouldn't be at
> a bad/incorrect state at this point to warrant a soft-reset. There will
> be a soft-reset when it goes through the initialization again.

It doesn't go through the initialization again unless we set 
-EPROBE_DEFER. And when we make ulpi_read_id() return -EPROBE_DEFER it 
will goto err0 here, so skips dwc3_core_soft_reset.

Do you mean you prefer something like:

if (ret) {

    if (ret == -ETIMEDOUT) ret = -EPROBE_DEFER;

    else goto err0;

}

> > +			ret = -EPROBE_DEFER;
> We shouldn't automatically set every error status to correspond to
> -EPROBE_DEFER. Check only the approapriate error codes (-ETIMEDOUT +
> any other?).
Other could be -ENOMEM. I think no need to do any new handling for that.
> >   			goto err0;
> > +		}
> >   		dwc->ulpi_ready = true;
> >   	}
> >   
> > --
> > 2.34.1
> Thanks,
> Thinh