[Bug 111621] Suspend/resume brightness issue Debian 8 with i965 integrated video controller

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=111621

--- Comment #11 from Jani Nikula <jani.nikula at intel.com> ---
(In reply to Aaron Lu from comment #5)
> You just need to type:
> # echo mem > /sys/power/state; dmesg > dmesg_after_resume; reboot
> after boot and then resume the machine, once the machine rebooted, the
> dmesg_after_resume should be under /root.

Please boot with drm.debug=14 module parameter and try this:

# echo mem > /sys/power/state; sleep 5; echo 300 >
/sys/class/backlight/intel_backlight/brightness; dmesg > dmesg_with_debug;
sleep 10; reboot

You can ^C at the sleep 10 if the echo there brings the backlight back.

(In reply to Aaron Lu from comment #10)
> I tend to think the backlight should be turned on by the GPU driver after
> resume, so I'll move this bug to GPU category to see if they have an idea.

Let's see. It may be a userspace bug, and there may be a bad interaction with
the two backlight drivers.

> But I guess they will also need you to test the latest kernel first :-)

Preferrably yes. v4.4 or later.

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