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

[Mark Zhang <markz@nvidia.com>]

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