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

[Ilpo Järvinen]

On Tue, 28 May 2019, Jani Nikula wrote:

> On Mon, 27 May 2019, Ashutosh Dixit <ashutosh.dixit at intel.com> wrote:
> > 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
> 
> Ilpo, does video=VGA-1:e command-line option work around the problem for
> you?

Yes it does; together with the modeline stuff for Xorg (after reading the 
referenced bug report I realized I can fix the X side with it). So I now 
have the desired modes/resolutions in use. Thank you all!

-- 
 i.