Re: [PATCH] ARM: dt: tegra: ventana: define pinmux for ddc

[Mark Zhang]

On 10/23/2012 01:14 AM, Stephen Warren wrote:
> On 10/22/2012 01:29 AM, Mark Zhang wrote:
> > On 10/19/2012 11:48 PM, Stephen Warren wrote:
> > > On 10/18/2012 11:58 PM, Mark Zhang wrote:
> > > > Define pinmux for DDC. The DDC pinmux in Ventana is 2 pins in I2C2.
> > >
> > > > +++ b/arch/arm/boot/dts/tegra20-ventana.dts
> > >
> > > > -            ddc {
> > > > -                nvidia,pins = "ddc", "owc", "spdi", "spdo",
> > > > -                    "uac";
> > > > -                nvidia,function = "rsvd2";
> > > > -            };
> > >
> > > So that removes the entries for 5 pin groups, yet below, entries are
> > > only added for the ddc and pta pingroups, so the other 4 pin groups
> > > become unconfigured.
> >
> > Right. So I think it should be changed to:
> >
> >          owc {
> >              nvidia,pins = "owc", "spdi", "spdo", "uac";
> >              nvidia,function = "rsvd2";
> >          };
> >
> > Is this right?
>
> Looks correct, yes.
>
> > > > +
> > > > +        state_i2cmux_ddc: pinmux_i2cmux_ddc {
> > > > +            ddc {
> > > > +                nvidia,pins = "ddc";
> > > > +                nvidia,function = "i2c2";
> > > > +            };
> > > > +            pta {
> > > > +                nvidia,pins = "pta";
> > > > +                nvidia,function = "rsvd4";
> > > > +            };
> > >
> > > Does this actually work? The pta pingroup is configured by the "hog"
> > > pinctrl state of the pinctrl node itself, so this state should fail to
> > > be applied since it attempts to touch the same pingroup.
> >
> > I know little about kernel pinctrl subsystem. After reading some docs
> > and codes, I think what you mean is, in Ventana's pinmux configuration,
> > pta pingroup has been defined as "hdmi" function and this can't be
> > changed(non-dynamic pinmuxing).
> > So I want to know why we have defined pta pingroup as hdmi function?
> > Can we remove this definition to make the i2cmux above working?
>
> I don't recall why pta was defined to be HDMI. The issue isn't that this
> patch changes the pinmux selection for the pta pingroup, but simply that
> both the pinctrl node's state definition, and the new I2C mux node's
> state definition both attempt to configure pingroup pta. The solution is
> most likely to simply remove the pta configuration from the main pinctrl
> node.

Understood. I tried to remove the hdmi function definition of pta 
pingroup yesterday then found HDMI can't work anymore. The EDID of HDMI 
monitor can't be fetched. After some debugging, I have found that it's 
caused by "i2c-mux-pinctrl" driver is loaded after drm driver. That 
makes drm driver can't get EDID data via this i2c mux adapter because it 
doesn't exist at that time. So I think we need to promote the load level 
of "i2c-mux-pinctrl" driver. Any other ideas?

Mark
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