[Bug 95476] [BXT-P] i915 driver overwrites the DDI PHY register for the 1366x768 panel with incorrect values

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=95476

Jani Nikula <jani.nikula at intel.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |NEEDINFO

--- Comment #2 from Jani Nikula <jani.nikula at intel.com> ---
(In reply to Tarun Vyas from comment #0)
> In the APL platforms, the firmware enables the 1366x768 panels by correctly
> programming the DDI PHY registers, but this leads to a PHY state mismatch
> according to the i915 driver because the driver expects to read a value from
> the PHY registers that differs from what was programmed by the firmware.
> Hence, the i915 driver goes ahead and reprograms the PHY, incorrectly,
> causing the DP link training to fail. The i915 driver will need
> modifications to correct this behavior. Filing this bug to track those
> modifications.

I get the impression you know where things go wrong; can you give more
specifics please?

Alternatively, please add 'intel_reg dump' output before and after loading the
i915 driver, i.e. register dumps with the values programmed by firmware and
i915, respectively.

The intel_reg tool is part of the intel-gpu-tools package 
http://cgit.freedesktop.org/xorg/app/intel-gpu-tools/

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