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* Troubleshooting LVDS on GM45.
@ 2016-04-01  4:49 Rob Kramer
  2016-04-01  8:01 ` Jani Nikula
                   ` (3 more replies)
  0 siblings, 4 replies; 19+ messages in thread
From: Rob Kramer @ 2016-04-01  4:49 UTC (permalink / raw)
  To: dri-devel

Hi,

My setup is an embedded GM45 based board with a screen connected via 24 
bit LVDS. When trying a to use a newer kernel (3.14.57) with KMS, the 
screen stays blank. I'm only testing KMS so far, no X. Older, pre-KMS 
versions of the kernel worked fine.

I'm hoping that a resident Intel DRM guru has an idea of what might be 
wrong here, or can tell me where to continue troubleshooting :)

I've uploaded a kernel log (drm.debug=0xe) here: 
http://pastebin.com/nYNRGW5B

The video kernel parameter for this log is: video=LVDS-1:1920x1080. I've 
tried others, M and/or R suffixes, loading edid/1920x1080.bin etc, but 
nothing works. I'm not sure if all this EDID timing stuff is even used 
for LVDS..

One line in the log mentions a mode that is promising:

   [    5.534021] [drm:intel_dump_crtc_timings], crtc timings: 148571 
1920 2040 2080 2200 1080 1097 1108 1125, type: 0x0 flags: 0xa

In the BIOS, the panel type is configured as "1920x1080@148.5M", so that 
looks good. I have no idea where that modeline came from though.

 From what I can see, LVDS-1 and CRTC 3 are connected, but when it's 
time to set the mode, it seems to have been modified into a bogus 
adjusted mode:

   [    5.570523] [drm:intel_dump_pipe_config], requested mode:
   [    5.570525] [drm:drm_mode_debug_printmodeline], Modeline 
0:"1920x1080" 0 172780 1920 2040 2248 2576 1080 1081 1084 1118 0x0 0x6
   [    5.570526] [drm:intel_dump_pipe_config], adjusted mode:
   [    5.570529] [drm:drm_mode_debug_printmodeline], Modeline 
0:"640x480" 0 148571 640 656 752 800 480 490 492 525 0x8 0x0
   [    5.570531] [drm:intel_dump_crtc_timings], crtc timings: 148571 
640 656 752 800 480 490 492 525, type: 0x8 flags: 0x0

Also, the dot-clock mentioned in the HD mode is now 172780, for some 
reason..

All sorts of kernel warnings follow, after this (what is LVDS-6?):

   [    5.570569] [drm:intel_crtc_mode_set], [ENCODER:6:LVDS-6] set 
[MODE:0:1920x1080]

Please let me know if you'd like more logging or details.

Cheers,

      Rob

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^ permalink raw reply	[flat|nested] 19+ messages in thread

end of thread, other threads:[~2017-10-09 16:48 UTC | newest]

Thread overview: 19+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-04-01  4:49 Troubleshooting LVDS on GM45 Rob Kramer
2016-04-01  8:01 ` Jani Nikula
2016-04-01  8:11   ` Rob Kramer
2016-04-01 10:07 ` Troubleshooting LVDS on GM45 (kernel 4.5.0) Rob Kramer
2016-04-01 11:11   ` Jani Nikula
2016-04-04  3:14     ` Rob Kramer
2016-04-04 14:58       ` Ville Syrjälä
2016-04-05  4:07         ` Rob Kramer
2016-04-01 15:37 ` [PATCH 1/2] drm/i915: Read timings from the correct transcoder in intel_crtc_mode_get() ville.syrjala
2016-04-01 15:37   ` [PATCH 2/2] drm/i915: Use intel_get_pipe_timings() and intel_mode_from_pipe_config() " ville.syrjala
2016-04-01 18:48     ` [PATCH v2 " ville.syrjala
2016-04-13 12:08       ` Ville Syrjälä
2017-09-25 19:19       ` Chris Wilson
2017-10-09 16:18         ` Ville Syrjälä
2017-10-09 16:24           ` Chris Wilson
2017-10-09 16:48             ` Ville Syrjälä
2017-09-25 14:18   ` [Intel-gfx] [PATCH 1/2] drm/i915: Read timings from the correct transcoder " Chris Wilson
2016-04-01 16:44 ` ✗ Fi.CI.BAT: warning for series starting with [1/2] " Patchwork
2016-04-01 17:14   ` Ville Syrjälä

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