VLV: eDP: panel timings / resolution data from VBT, not via i2c from eDP EDID

VLV: eDP: panel timings / resolution data from VBT, not via i2c from eDP EDID

[Lampersperger Andreas]

Hello Gajanan,

I'm trying to run linux on a 
valleyview hardware, which was made by my company. 

On this hardware, the display panel is connected via 
eDP, but the panel timings / resolution is not available 
in the EDID of the eDP. It is only available via VBT. 

You added once eDP support to VLV, can you 
give me some information on the following questions:

Is there a way to force the i915.ko to get the 
panel timing / resolution for the eDP from the 
VBT and not via i2c from the eDP?

Can you give me some advice, how to add this 
option to the source files of i915.ko?

I'm using 3.14.29, but I have also tried 4.0.0-rc7.

Best regards
Andreas










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Re: VLV: eDP: panel timings / resolution data from VBT, not via i2c from eDP EDID

[Jani Nikula]

On Thu, 09 Apr 2015, Lampersperger Andreas <lampersperger.andreas@heidenhain.de> wrote:
> Hello Gajanan,
>
> I'm trying to run linux on a 
> valleyview hardware, which was made by my company. 
>
> On this hardware, the display panel is connected via 
> eDP, but the panel timings / resolution is not available 
> in the EDID of the eDP. It is only available via VBT. 

We seem to try to use the modes from EDID if available. Does the panel
not respond to EDID requests, or does it have incorrect EDID
information?

We only fallback to trying the mode from VBT if no modes can be found
from EDID.

> You added once eDP support to VLV, can you 
> give me some information on the following questions:
>
> Is there a way to force the i915.ko to get the 
> panel timing / resolution for the eDP from the 
> VBT and not via i2c from the eDP?
>
> Can you give me some advice, how to add this 
> option to the source files of i915.ko?
>
> I'm using 3.14.29, but I have also tried 4.0.0-rc7.

See intel_edp_init_connector() in drivers/gpu/drm/i915/intel_dp.c, look
at how fixed_mode is set.

Maybe you can change that to prefer VBT.

An alternative would be to get EDID using the firmware loading
interface, but also for that you'd have to call drm_load_edid_firmware()
in intel_edp_init_connector() instead of drm_get_edid().

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Technology Center
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