Re: [PATCH 1/3] Documentation: dt: dwc3: Add snps,configure-fladj property

Mark Rutland
2015-07-23T10:57:29Z

On Thu, Jul 23, 2015 at 11:52:19AM +0100, Badola Nikhil wrote:
> > -----Original Message-----
> > From: Mark Rutland [mailto:mark.rutland-5wv7dgnIgG8@public.gmane.org]
> > Sent: Thursday, July 23, 2015 3:27 PM
> > To: Badola Nikhil-B46172
> > Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; balbi-l0cyMroinI0@public.gmane.org
> > Subject: Re: [PATCH 1/3] Documentation: dt: dwc3: Add snps,configure-fladj
> > property
> >
> > On Thu, Jul 23, 2015 at 11:09:21AM +0100, Nikhil Badola wrote:
> > > Add property snps,configure-fladj for enabling post silicon frame
> > > length adjustment
> > >
> > > Signed-off-by: Nikhil Badola <nikhil.badola-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
> > > ---
> > > Documentation/devicetree/bindings/usb/dwc3.txt | 1 +
> > > 1 file changed, 1 insertion(+)
> > >
> > > diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt
> > > b/Documentation/devicetree/bindings/usb/dwc3.txt
> > > index 0815eac..90c3972 100644
> > > --- a/Documentation/devicetree/bindings/usb/dwc3.txt
> > > +++ b/Documentation/devicetree/bindings/usb/dwc3.txt
> > > @@ -40,6 +40,7 @@ Optional properties:
> > > - snps,hird-threshold: HIRD threshold
> > > - snps,hsphy_interface: High-Speed PHY interface selection between
> > "utmi" for
> > > UTMI+ and "ulpi" for ULPI when the DWC_USB3_HSPHY_INTERFACE has
> > value 3.
> > > + - snps,configure-fladj: enables post-silicon frame length adjustment
> >
> > Could you elaborate on what this means and why you think it's necessary?
>
> This property enables the use of GFLADJ_30MHZ field value of gfladj register for frame length
> adjustment instead of considering from the sideband input signal fladj_30mhz_reg from SOC.
> This is required when signal fladj_30mhz_reg is connected to a wrong value or is not valid as
> in our case, hence post-silicon.

Ok, so this is basically an override for the GFLADJ_30MHZ field of the
gfladj register when there was a problem at integration time.

> However this field can be used to adjust any offset ranging from 00h to 3Fh, from the
> clock source generating SOF(start of frame) packets. Thus, this property can be added to device
> tree with appropriate adjustment value.

It takes a value? The description above makes it sound like a boolean
property.

I'd expect a description more like:

- snps,fladj-override: Value for GFLADJ_30MHZ when the fladj_30mhz_reg
signal is invalid or incorrect.

Which makes it clear what the value is and when it should be set.

Thanks,
Mark.