Re: back light conflict i915 vs dell-laptop

[Patrick Schaaf]

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


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