[Bug 97883] [i915] intel_backlight does not function - Lenovo X1 Yoga OLED

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=97883

Benjamin Lorenz <lorenz at math.tu-berlin.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |lorenz at math.tu-berlin.de

--- Comment #30 from Benjamin Lorenz <lorenz at math.tu-berlin.de> ---
Created attachment 137494
  --> https://bugs.freedesktop.org/attachment.cgi?id=137494&action=edit
/dev/drm_dp_aux0 from X1 Yoga 2nd gen OLED

(In reply to Jani Nikula from comment #28)
> If anyone can enable CONFIG_DRM_DP_AUX_CHARDEV=y and dump the DPCD using the
> aux chardev (IIRC should pop up somewhere under /sys/class/drm/card0-eDP-1),
> it might give some clues.

Almost full DPCD data from X1 Yoga 2nd generation is attached.

Reading it with cat gives only the first few bytes and several
[drm:intel_dp_aux_ch] *ERROR* dp_aux_ch receive error status 0x6f4003ff
in dmesg.
ddrescue was able to extract everything except for byte 0x53:
#      pos        size  status
0x00000000  0x00000053  +
0x00000053  0x00000001  -
0x00000054  0x000FFFAC  +

The file is zeros except for the following parts:
00000000: 120a 8441 0000 0180 0200 0000 0f0b 0000  ...A............
00000060: 0111 0100 0100 0100 0001 0600 0000 0000  ................
00000070: 010b 0000 0000 0000 0000 0000 0000 0000  ................
00000100: 0a84 0000 0000 0000 0108 0000 0000 0000  ................
00000200: 0100 7777 0101 0000 0000 0000 0000 0000  ..ww............
00000210: 0080 0080 0080 0080 000a 0000 0000 0000  ................
00000220: 0400 0000 0000 0000 0000 0000 0002 0000  ................
00000240: c440 b354 9810 2200 0000 0000 0000 0000  . at .T..".........
00000300: 0000 0000 0000 0000 0000 0000 0200 0000  ................
00000320: 0100 0000 0000 0000 0000 0000 0000 0000  ................
00000400: 001c f800 0000 0000 0001 1b14 0316 0000  ................
00000410: 0000 0080 0080 0000 0000 0000 0000 0000  ................
00000600: 0100 0000 0000 0000 0000 0000 0000 0000  ................
00000700: 028a ef00 0000 0000 0000 0000 0000 0000  ................
00000720: 0000 ffc0 0a03 0a00 0100 0010 00ff 0000  ................
00000730: 0000 0014 0000 0000 0000 0000 0000 0000  ................
00002000: 0000 0000 0002 0000 0008 0000 7777 0101  ............ww..

Thanks a lot for looking into this!

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