Bug 88071

Summary:	Screen stays off if DPMS is set to off and then on again
Product:	Drivers	Reporter:	Gabriele Mazzotta (gabriele.mzt)
Component:	Video(DRI - Intel)	Assignee:	intel-gfx-bugs (intel-gfx-bugs)
Status:	RESOLVED MOVED
Severity:	normal	CC:	chris, gabriele.mzt, intel-gfx-bugs
Priority:	P1
Hardware:	x86-64
OS:	Linux
Kernel Version:	3.18-rc3	Subsystem:
Regression:	Yes	Bisected commit-id:

Description Gabriele Mazzotta 2014-11-11 21:02:06 UTC

If the screen is on and I run "xset dpms force off", I have to manually set
bl_power to 0 in order to turn the screen on again.

Here some data I collected.

* If the screen is off and set dpms to off, I get:
cat /sys/class/drm/card0/card0-DP-1/dpms
On
cat /sys/class/drm/card0/card0-eDP-1/dpms
Off
cat /sys/class/backlight/intel_backlight/bl_power
4
cat /sys/class/backlight/intel_backlight/brightness
0

* If I try to turn the screen on by pressing any key, I get:
cat /sys/class/drm/card0/card0-DP-1/dpms
On
cat /sys/class/drm/card0/card0-eDP-1/dpms
On
cat /sys/class/backlight/intel_backlight/bl_power
1
cat /sys/class/backlight/intel_backlight/brightness
94

* At this point, to turn the screen on, I have to toggle bl_power.


lspci:
00:02.0 VGA compatible controller: Intel Corporation Haswell-ULT Integrated Graphics Controller (rev 09)

Comment 1 Gabriele Mazzotta 2014-11-11 21:04:03 UTC

I'm sorry, in the first point I meant to write:
"If the screen is on and set dpms to off, I get:"
instead of
"If the screen is off and set dpms to off, I get:"

Comment 2 Chris Wilson 2014-11-11 21:07:54 UTC

commit 7ecc778691c452285f754743a93a46fa1d3da52f
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Tue Nov 4 10:36:26 2014 +0000

    backlight: bl_power uses 0 for on and 4 for off
    
    The backlight/bl_power file didn't obey the obvious semantics, but
    instead operates using some interesting framebuffer API. Oh well.
    
    Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

Comment 3 Gabriele Mazzotta 2014-11-11 21:35:22 UTC

Thanks for pointing the fix, I haven't seen it.