EDID/DP color precision fixes on Intel hw for stable

[Mario Kleiner]

Ping? Could somebody give this a review? Would be good to get the 
associated regressions in DVI/VGA output precision fixed in intel
hw, also for stable kernels which regressed.

Resending the three patches...

thanks,
-mario

On 03/28/2016 01:52 AM, Mario Kleiner wrote:
> Bugzilla https://bugzilla.kernel.org/show_bug.cgi?id=105331
>
> received a potential fix that was backported to stable. While that
> patch itself is correct for treating DP video sinks with "unknown
> color depth", it uncovered some lack in our general EDID 1.3
> handling, and in how we treat DP->DVI/VGA, causing the fall back
> of Intel DP to 6 bpc / 18 bpp in cases where it shouldn't fall
> back. That leads to unhappy neuroscience/medical users of Intel gpus
> which need their DP->DVI or DP->VGA display devices to operate at at
> least 8 bpc without dithering.
>
> The following three patches try to improve our EDID handling and
> Intel DP to try harder to detect the proper bpc to avoid these
> regressions for DP-DVI and DP-VGA. The third patch tries to fix
> FDO bug 105331 without causing general unhappiness of other users.
>
> thanks,
> -mario
>