[Bug 107583] New: Linux: REGRESSION: drm: cmdline EDID override mechanisms broken since 4.15

[bugzilla-daemon at freedesktop.org]

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

            Bug ID: 107583
           Summary: Linux: REGRESSION: drm: cmdline EDID override
                    mechanisms broken since 4.15
           Product: DRI
           Version: unspecified
          Hardware: x86-64 (AMD64)
               URL: https://bugs.debian.org/906180
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: pabs3 at bonedaddy.net
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 141115
  --> https://bugs.freedesktop.org/attachment.cgi?id=141115&action=edit
dmesg with the patch included

Forwarding https://bugs.debian.org/906180

linux.git commit 53fd40a90f3c caused the Linux kernel cmdline EDID override
mechanism to no longer override the EDID properly.

I have an external monitor that used to have a valid EDID but after replugging
it at one point, the EDID became empty. I recovered a copy of it from backups
of the Xorg logs. To get a valid EDID I then override the empty EDID using the
backup copy and the drm.edid_firmware (or drm_kms_firmware.edid_firmware)
parameter.

With the EDID correctly overridden, the VGA-1 EDID file looks like the
following, the Linux virtual consoles are higher resolution, GNOME/xrandr are
able to use the full resolution of the monitor (1680x1050) and GNOME is able to
determine the make/model (it is an LG FLATRON W2242PM but GNOME says Goldstar
Company Ltd 23"):

$ hd /sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-VGA-1/edid
00000000  00 ff ff ff ff ff ff 00  1e 6d 77 56 64 78 09 00  |.........mwVdx..|
00000010  08 13 01 03 6a 31 20 78  ea ae c5 a2 57 4a 9c 25  |....j1 x....WJ.%|
00000020  12 50 54 a7 6b 80 95 0f  95 00 81 80 81 40 71 4f  |.PT.k........ at qO|
00000030  01 01 01 01 01 01 7c 2e  90 a0 60 1a 1e 40 30 20  |......|...`.. at 0 |
00000040  36 00 da 28 11 00 00 1a  21 39 90 30 62 1a 27 40  |6..(....!9.0b.'@|
00000050  68 b0 36 00 da 28 11 00  00 1c 00 00 00 fd 00 38  |h.6..(.........8|
00000060  4b 1e 53 0f 00 0a 20 20  20 20 20 20 00 00 00 fc  |K.S...      ....|
00000070  00 57 32 32 34 32 0a 20  20 20 20 20 20 20 00 5d  |.W2242.       .]|
00000080

Without the override working correctly, the EDID file is empty, the Linux
virtual consoles are lower resolution and only the standard modes (1024x768,
800x600 and 848x480) are available in xrandr/GNOME and GNOME settings is not
able to determine the make/model of the monitor.

In addition to using the EDID override, I can manually run some xrandr commands
but that isn't as convenient and doesn't alter the resolution of the Linux
virtual consoles:

xrandr  --output VGA-1 --newmode 1680x1050_60.0  146.25  1680 1784 1960 2240 
1050 1053 1059 1089 -hsync +vsync
xrandr --addmode VGA-1 1680x1050_60.0
xrandr --output VGA-1 --mode 1680x1050_60.0
xrandr --output VGA-1 --auto

Adding video=VGA-1:e to the Linux kernel command-line parameters seems to fix
the EDID override problem.

I will attach dmesg files with the drm.debug=14 Linux kernel command-line
parameter.

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