Bug 75091 - Backlight is permanently turned off on screen blank
Backlight is permanently turned off on screen blank
Status: CLOSED UNREPRODUCIBLE
Product: ACPI
Classification: Unclassified
Component: Other
x86-64 Linux
: P1 normal
Assigned To: acpi_other
:
Depends on:
Blocks:
  Show dependency treegraph
 
Reported: 2014-04-29 19:07 UTC by Nicklas W Bjurman
Modified: 2014-06-23 01:02 UTC (History)
4 users (show)

See Also:
Kernel Version: linux 3.14.1
Tree: Mainline
Regression: No


Attachments

Description Nicklas W Bjurman 2014-04-29 19:07:17 UTC
When then screen goes blank on my laptop after 10 minutes of inactivity the backlight is turned off and brightness function keys do not respond.

To turn the backlight on again, I have to write a 1 to /sys/class/backlight/intel_backlight/bl_power or if the screen blanks again I have to write a 0 to turn the backlight on.
Comment 1 Aaron Lu 2014-05-16 08:20:53 UTC
(In reply to Nicklas W Bjurman from comment #0)
> When then screen goes blank on my laptop after 10 minutes of inactivity the
> backlight is turned off and brightness function keys do not respond.

Does the function key work OK before the dim happened?

> 
> To turn the backlight on again, I have to write a 1 to
> /sys/class/backlight/intel_backlight/bl_power or if the screen blanks again
> I have to write a 0 to turn the backlight on.

This is interesting. I don't know that bl_power has such effects, from the GPU driver code, it doesn't seem to do anything for bl_power change. Does the interface work well normally? i.e. if you echo a value in the range of 0-max_brightness to brightness file, does it work well?
Comment 2 Nicklas W Bjurman 2014-05-22 16:33:14 UTC
(In reply to Aaron Lu from comment #1)
> (In reply to Nicklas W Bjurman from comment #0)
> > When then screen goes blank on my laptop after 10 minutes of inactivity the
> > backlight is turned off and brightness function keys do not respond.
> 
> Does the function key work OK before the dim happened?

Yes, the function keys works as normal both before it happens once and after I fixed it when it does happen.

> > 
> > To turn the backlight on again, I have to write a 1 to
> > /sys/class/backlight/intel_backlight/bl_power or if the screen blanks again
> > I have to write a 0 to turn the backlight on.
> 
> This is interesting. I don't know that bl_power has such effects, from the
> GPU driver code, it doesn't seem to do anything for bl_power change. Does
> the interface work well normally? i.e. if you echo a value in the range of
> 0-max_brightness to brightness file, does it work well?

max_brightness is 255000 which is also the value of bl_power before it happens. I can not write to /sys/class/backlight/intel_backlight/bl_power

If I want to change the brightness I manually I need to write a value to /sys/class/backlight/acpi0_video/brightness in the range of 0 and /sys/class/backlight/acpi0_video/max_brightness(which happens to be 7).
Comment 3 Nicklas W Bjurman 2014-05-22 16:35:01 UTC
(In reply to Nicklas W Bjurman from comment #2)
> (In reply to Aaron Lu from comment #1)
> > (In reply to Nicklas W Bjurman from comment #0)

> > 
> > This is interesting. I don't know that bl_power has such effects, from the
> > GPU driver code, it doesn't seem to do anything for bl_power change. Does
> > the interface work well normally? i.e. if you echo a value in the range of
> > 0-max_brightness to brightness file, does it work well?
> 
> max_brightness is 255000 which is also the value of bl_power before it
> happens. I can not write to /sys/class/backlight/intel_backlight/bl_power

Clarification I can write values /sys/class/backlight/intel_backligt/to bl_power without any errors but if I cat bl_power it will remain 255000.
Comment 4 Nicklas W Bjurman 2014-05-22 16:40:23 UTC
(In reply to Nicklas W Bjurman from comment #3)
> (In reply to Nicklas W Bjurman from comment #2)
> > (In reply to Aaron Lu from comment #1)
> > > (In reply to Nicklas W Bjurman from comment #0)
> 
> > > 
> > > This is interesting. I don't know that bl_power has such effects, from the
> > > GPU driver code, it doesn't seem to do anything for bl_power change. Does
> > > the interface work well normally? i.e. if you echo a value in the range of
> > > 0-max_brightness to brightness file, does it work well?
> > 
> > max_brightness is 255000 which is also the value of bl_power before it
> > happens. I can not write to /sys/class/backlight/intel_backlight/bl_power
> 
> Clarification I can write values /sys/class/backlight/intel_backligt/to
> bl_power without any errors but if I cat bl_power it will remain 255000.

Sorry my mistake again, I retried to write to bl_power and then cat and it did indeed change from 255000 to my given value but there is no effect on the the backlight. Doesn't matter whether I write 0 or 10000. Nothing happens before the backlight is turned off by the screen blanking.
Comment 5 Nicklas W Bjurman 2014-05-22 16:45:43 UTC
(In reply to Aaron Lu from comment #1)
> (In reply to Nicklas W Bjurman from comment #0)
> > When then screen goes blank on my laptop after 10 minutes of inactivity the
> > backlight is turned off and brightness function keys do not respond.
> 
> Does the function key work OK before the dim happened?
> 
> > 
> > To turn the backlight on again, I have to write a 1 to
> > /sys/class/backlight/intel_backlight/bl_power or if the screen blanks again
> > I have to write a 0 to turn the backlight on.
> 
> This is interesting. I don't know that bl_power has such effects, from the
> GPU driver code, it doesn't seem to do anything for bl_power change. Does
> the interface work well normally? i.e. if you echo a value in the range of
> 0-max_brightness to brightness file, does it work well?

I never had this problem until rescently. I am running Archlinux and hadn't updated the system for a while so I can not pinpoint the exact time it happen.
Screen blanking didn't work at all in 2.6.X, it started to work during 3.X and I believe this appeared at least after 3.12(not so certain what kernel version I had installed before I updated and this bug appeared).
Comment 6 Aaron Lu 2014-05-23 01:47:57 UTC
When the backlight is off due to dim, I think you can write any value to bl_power of intel_backlight to bring backlight back, since from the code, what the store of bl_power does is to set the previous backlight level again.

When the backlight is off due to dim, can you please ssh to the machine to see what brightness values are of both the acpi_video and intel_backlight interfaces?
/sys/class/backlight/xxx/brightness

BTW, I'm not clear what the GUI you use does to dim the screen. Any chance to disable it so that we can verify if this is caused by GUI or kernel?
Comment 7 Zhang Rui 2014-06-03 07:03:57 UTC
ping ...
Comment 8 Nicklas W Bjurman 2014-06-03 07:23:21 UTC
Sorry to not have replied, I will try to ssh into the machine within short. I use openbox, I will try to start the machine without X and see what happens. Sorry for the long delay.
Comment 9 Hans de Goede 2014-06-16 09:20:05 UTC
This sounds like a duplicate of bug 79423 to me.
Comment 10 Hans de Goede 2014-06-16 09:20:44 UTC
Oops different bugzilla I mean as a duplicate of:
https://bugs.freedesktop.org/show_bug.cgi?id=79423
Comment 11 Nicklas W Bjurman 2014-06-16 09:26:05 UTC
I do not think think it is the same. The backlight works perfectly when I start the laptop. The problem is that the backlight stays turned off after the laptop shuts off the screen in energy saving mode.
Comment 12 Nicklas W Bjurman 2014-06-21 18:54:35 UTC
Sorry guys, I missed the opportunity to do any more research on this bug. The backlight on my laptop gave up and when i tried to fix it... Well, lets just say that I have no laptop anylonger.
Comment 13 xerofoify 2014-06-22 02:59:52 UTC
Would you guys mind closing this bug as his laptop is 
dead and that seems to be the issue.
Thanks Nick

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