Re: [PATCH] tegra: ventana: display and backlight DT entries

[Mark Zhang <markz-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>]

On 11/14/2012 12:46 AM, Stephen Warren wrote:
> On 11/13/2012 05:34 AM, Thierry Reding wrote:
>> On Tue, Nov 13, 2012 at 07:23:24PM +0900, Alexandre Courbot wrote:
>>> Enable internal panel: - add EDID file - add power sequence to
>>> control backlight and panel (panel is currently controlled by the
>>> backlight sequence, this will need to be fixed once the panel
>>> framework has power sequences support)
>>>
>>> Also enable HDMI output.
> 
>>> diff --git a/arch/arm/boot/dts/tegra20-ventana.dts
>>> b/arch/arm/boot/dts/tegra20-ventana.dts
> 
>>> +			rgb { +				status = "okay"; +				nvidia,edid =
>>> /incbin/("tegra20-ventana.edid");
>>
>> We've briefly discussed this on IRC already, but for the sake of 
>> completeness I'll restate it here. I think this should be converted
>> to the bindings as defined by the videomode helpers. These are not
>> merged yet, but they provide a much more readable representation
>> than a binary blob.
>>
>> I know that Stephen mentioned using the nvidia,edid property for
>> boards where the blob is actually available in some sort. I seem to
>> remember him mentioning Ventana in particular, but I may be wrong.
> 
> I do tend to think that we should use EDID where there is one.
> 
> 1) If there is an EDID in the panel HW, and the panel's I2C is hooked
> up to Tegra, we should read it out at runtime.
> 
> 2) Otherwise, if the panel's documentation provides an EDID, we should
> use that, since it's the most canonical/common/standard representation
> of the panel's properties.
> 
> 3) Otherwise, use the videomode DT bindings.
> 
> Another benefit of (2) is that we can actually support the panel
> without waiting for the videomode DT bindings to be finalized and merged.
> 

Basically I agree with you. Although EDID blob is not friendly to read
but it's more flexible.
In addition, I recall I can use "i2cget" to get the EDID of Ventana's
panel but I've no idea why we can't do that in drm driver. I can spend
some time to take a look at this again and if the EDID can be fetched
dynamically, I think it's no need to consider videomode DT bindings
anymore.

> Although if Ventana requires the power sequences helpers, that already
> means we won't be able to support Ventana's panel in 3.8 unless the
> power sequences code gets merged for 3.8; is that likely?
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