Re: [PATCH v2] net/phy/vitesse: Configure RGMII skew on VSC8601, if needed

[Alex]

On 11/16/2016 08:54 AM, Andrew Lunn wrote:
> On Wed, Nov 16, 2016 at 08:44:30AM -0800, Alex wrote:
> > On 11/16/2016 05:50 AM, Andrew Lunn wrote:
> > > On Wed, Nov 16, 2016 at 01:02:33AM -0800, Alexandru Gagniuc wrote:
> > > > With RGMII, we need a 1.5 to 2ns skew between clock and data lines. The
> > > > VSC8601 can handle this internally. While the VSC8601 can set more
> > > > fine-grained delays, the standard skew settings work out of the box.
> > > > The same heuristic is used to determine when this skew should be enabled
> > > > as in vsc824x_config_init().
> > > >
> > > > +/* This adds a skew for both TX and RX clocks, so the skew should only be
> > > > + * applied to "rgmii-id" interfaces. It may not work as expected
> > > > + * on "rgmii-txid", "rgmii-rxid" or "rgmii" interfaces. */
> > >
> > > Hi Alexandru
> > >
> > > You should be able to make "rgmii" work as expected. If that is the
> > > phy mode, disable the skew.
> >
> > And that's exactly the implemented behavior. See
> > vsc8601_config_init() below.
>
> I don't think so. vsc8601_config_init() will not cause the skew to be
> cleared if the phy-mode is "rgmii" and something else like the
> bootloader could of set the skew. So saying that "rgmii" might not
> work as expected is true. But with a minor change, you can make it
> work as expected.

That's not within the scope of this change. The scope is to make 
rgmii-id work. Any additional changes would be untested.

Alex