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

[Thierry Reding <thierry.reding-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>]

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On Wed, Nov 14, 2012 at 01:56:45PM +0800, Mark Zhang wrote:
> On 11/14/2012 01:36 PM, Alex Courbot wrote:
> > On Wednesday 14 November 2012 00:46:52 Stephen Warren wrote:
> >> 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.
> > 
> > According to Ventana' platform design guide the LCD panel is hooked on I2C2. 
> > The panel's data sheet lists CLK_EDID and DATA_EDID pins, which I assume are 
> > for I2C, but there is no mention of an I2C address in both guides.
> > 
> 
> Normally the address is 0x50. Take a look at function
> "drm_do_probe_ddc_edid" as a reference.
> 
> >> 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.
> > 
> > Panel's documentation indeed provides full EDID specification in appendix. Mark 
> > sent me an EDID blob which works but I don't know where it comes from - Mark, 
> > could you tell us?
> > 
> 
> Actually I use a tool named "i2cget" to get this 128 bytes EDID. For
> Ventana, I use a script like this:
> 
> for i in  $(seq 0 127)
> do
> 	#echo " Reading byte no : $i "
> 	i2cget -y 0 0x50 $i | xxd -r -p >> tegra20-ventana.edid
> done

There is also i2cdump but I suppose for writing the data into a binary
file it isn't as well suited as the above loop. I seem to remember a
tool that could be used to dump EDID directly, but I can't get a fix on
the name.

Anyway, if you can get the EDID data that way it should also be possible
to get it directly within tegra-drm.

Thierry

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