DRM/AST regression (likely 4.14 -> 4.19+), providing EDID manually fails

[Ashutosh Dixit]

On Sun, 26 May 2019 12:50:51 -0700, Ilpo Järvinen wrote:
>
> Hi all,
>
> I've a workstation which has internal VGA that is detected as AST 2400 and
> with it EDID has been always quite flaky (except for some time it worked
> with 4.14 long enough that I thought the problems would be past until the
> problems reappeared also with 4.14). Thus, I've provided manually the EDID
> that I extracted from the monitor using other computer (the monitor itself
> worked just fine on the earlier computer so it is likely fine).
>
> I setup the manual EDID using drm_kms_helper.edid_firmware, however,
> after upgrading to 4.19.45 it stopped working (no "Got external EDID base
> block" appears in dmesg, the text mode is kept in the lower res mode, and
> Xorg logs no longer dumps the EDID info like it did with 4.14). So I guess
> the EDID I provided manually on the command line is not correctly put into
> use with 4.19+ kernels.
>
> The 4.19 dmesg indicated that drm_kms_helper.edid_firmware is deprecated
> so I also tested with drm.edid_firmware it suggested as the replacement
> but with no luck (but I believe also the drm_kms_helper one should have
> worked as it was only "deprecated").
>
> I also tried 5.1.2 but it did not work any better (and with it also tried
> removing all the manual *.edid_firmware from the command line so I still
> need to provide one manually to have it reliable working it seems).

I believe there is a bug already tracking this, here:

https://bugs.freedesktop.org/show_bug.cgi?id=107583