Re: back light conflict i915 vs dell-laptop

[Patrick Schaaf <bof@bof.de>]

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On Thu, 2010-11-25 at 12:33 +0300, Dan Carpenter wrote:
> Patrick Schaaf has reported that the i915 driver is setting his
> backlight very dim when he starts GDM.
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=23472
> 
> It should be the dell-laptop platform driver controlling his backlight.
> 
> Gnome tries to restore the backlight settings through the dell_laptop
> interface in sysfs but it fails.  (Because the platform hardware refuses
> to set the settings to what it thinks they already are).

As far as my instrumentation showed, gnome did try no such thing - there
were no setting calls through the backlight interface when I switch
between the GDM screen and text console.

I have now run with drm.debug=0x07 and noticed get/set backlight PWM
messages from intel_panel_get/set_backlight which became lower and lower
in value for each successive switching between GDM login screen and text
console, until reaching a low point and overflowing to 255255.

I append the extract of these kernel messages, as well as putting them
in the bugzilla entry linked above.

Hope this helps clarify the problems I'm seeing.

best regards
  Patrick



[-- Attachment #2: intel_panel_..._backlight --]
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Nov 28 18:43:17 lat1 kernel: [   61.454973] [drm:intel_panel_get_backlight], get backlight PWM = 127500
Nov 28 18:43:17 lat1 kernel: [   61.672115] [drm:intel_panel_set_backlight], set backlight PWM = 127500
Nov 28 18:43:25 lat1 kernel: [   69.659366] [drm:intel_panel_get_backlight], get backlight PWM = 63627
Nov 28 18:43:25 lat1 kernel: [   69.876223] [drm:intel_panel_set_backlight], set backlight PWM = 63627
Nov 28 18:45:02 lat1 kernel: [  166.642624] [drm:intel_panel_get_backlight], get backlight PWM = 126735
Nov 28 18:45:02 lat1 kernel: [  166.861225] [drm:intel_panel_set_backlight], set backlight PWM = 126735
Nov 28 18:45:06 lat1 kernel: [  169.869343] [drm:intel_panel_get_backlight], get backlight PWM = 63246
Nov 28 18:45:06 lat1 kernel: [  170.086225] [drm:intel_panel_set_backlight], set backlight PWM = 63246
Nov 28 18:50:24 lat1 kernel: [  488.561922] [drm:intel_panel_get_backlight], get backlight PWM = 31563
Nov 28 18:50:24 lat1 kernel: [  488.780228] [drm:intel_panel_set_backlight], set backlight PWM = 31563
Nov 28 18:50:29 lat1 kernel: [  492.905273] [drm:intel_panel_get_backlight], get backlight PWM = 15776
Nov 28 18:50:29 lat1 kernel: [  493.122220] [drm:intel_panel_set_backlight], set backlight PWM = 15776
Nov 28 18:50:45 lat1 kernel: [  509.449869] [drm:intel_panel_get_backlight], get backlight PWM = 7888
Nov 28 18:50:45 lat1 kernel: [  509.667228] [drm:intel_panel_set_backlight], set backlight PWM = 7888
Nov 28 18:50:48 lat1 kernel: [  512.061427] [drm:intel_panel_get_backlight], get backlight PWM = 3944
Nov 28 18:50:48 lat1 kernel: [  512.278220] [drm:intel_panel_set_backlight], set backlight PWM = 3944
Nov 28 18:50:54 lat1 kernel: [  518.938610] [drm:intel_panel_get_backlight], get backlight PWM = 1972
Nov 28 18:50:55 lat1 kernel: [  519.156232] [drm:intel_panel_set_backlight], set backlight PWM = 1972
Nov 28 18:50:58 lat1 kernel: [  522.665295] [drm:intel_panel_get_backlight], get backlight PWM = 986
Nov 28 18:50:58 lat1 kernel: [  522.883222] [drm:intel_panel_set_backlight], set backlight PWM = 986
Nov 28 18:51:04 lat1 kernel: [  528.338612] [drm:intel_panel_get_backlight], get backlight PWM = 493
Nov 28 18:51:04 lat1 kernel: [  528.557235] [drm:intel_panel_set_backlight], set backlight PWM = 493
Nov 28 18:51:07 lat1 kernel: [  531.697225] [drm:intel_panel_get_backlight], get backlight PWM = 246
Nov 28 18:51:07 lat1 kernel: [  531.915244] [drm:intel_panel_set_backlight], set backlight PWM = 246
Nov 28 18:51:20 lat1 kernel: [  544.747370] [drm:intel_panel_get_backlight], get backlight PWM = 123
Nov 28 18:51:20 lat1 kernel: [  544.965241] [drm:intel_panel_set_backlight], set backlight PWM = 123
Nov 28 18:51:24 lat1 kernel: [  548.220386] [drm:intel_panel_get_backlight], get backlight PWM = 61
Nov 28 18:51:24 lat1 kernel: [  548.437215] [drm:intel_panel_set_backlight], set backlight PWM = 61
Nov 28 18:51:31 lat1 kernel: [  555.916888] [drm:intel_panel_get_backlight], get backlight PWM = 30
Nov 28 18:51:32 lat1 kernel: [  556.134239] [drm:intel_panel_set_backlight], set backlight PWM = 30
Nov 28 18:51:35 lat1 kernel: [  559.138346] [drm:intel_panel_get_backlight], get backlight PWM = 15
Nov 28 18:51:35 lat1 kernel: [  559.355242] [drm:intel_panel_set_backlight], set backlight PWM = 15
Nov 28 18:51:40 lat1 kernel: [  564.929606] [drm:intel_panel_get_backlight], get backlight PWM = 7
Nov 28 18:51:41 lat1 kernel: [  565.148225] [drm:intel_panel_set_backlight], set backlight PWM = 7
Nov 28 18:51:45 lat1 kernel: [  569.509391] [drm:intel_panel_get_backlight], get backlight PWM = 3
Nov 28 18:51:45 lat1 kernel: [  569.726226] [drm:intel_panel_set_backlight], set backlight PWM = 3
Nov 28 18:51:52 lat1 kernel: [  576.103569] [drm:intel_panel_get_backlight], get backlight PWM = 1
Nov 28 18:51:52 lat1 kernel: [  576.322226] [drm:intel_panel_set_backlight], set backlight PWM = 1
Nov 28 18:51:56 lat1 kernel: [  579.760386] [drm:intel_panel_get_backlight], get backlight PWM = 0
Nov 28 18:51:56 lat1 kernel: [  579.977224] [drm:intel_panel_set_backlight], set backlight PWM = 255255
Nov 28 18:52:12 lat1 kernel: [  596.022674] [drm:intel_panel_get_backlight], get backlight PWM = 127500
Nov 28 18:52:12 lat1 kernel: [  596.241232] [drm:intel_panel_set_backlight], set backlight PWM = 127500
Nov 28 18:52:15 lat1 kernel: [  599.502386] [drm:intel_panel_get_backlight], get backlight PWM = 63627
Nov 28 18:52:15 lat1 kernel: [  599.719217] [drm:intel_panel_set_backlight], set backlight PWM = 63627