[Bug 73971] Intel i915 screen remains blank when resuming from suspend

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=73971

--- Comment #14 from Denis Leclair <denis at theleclairs.ca> ---

Ok, here is more data on the suspend/resume issue.

This dmesg was taken after a normal boot with drm.debug=0xe:
http://pastebin.centos.org/8986/


This second dmesg was taken from ssh into the laptop while it had the blank
screen during the attempt to resume: http://pastebin.centos.org/8991/


In this second one, we see two more errors with backtraces on top of the first
one.
   - The first one is in i915_request_power_well()
   - The second one is in i915_release_power_well()
   - The third one is in i915_request_power_well()

It seems like all three of these step from the hda_display_power() function
which if I understand correctly is related to the HD audio controller so I'm
not sure how that would relate to the display not turning on but it doesn't
seem right.


I also pulled down the latest drm-intel source code and started looking around
in there. I came across a comment for 810 driver which essentially said that
the BIOS may keep VGA ports powered down unless there is a monitor present at
power-up.

I haven't had a monitor present in any of my testing so could that be part of
the problem? I've simply been looking to see that the display port shows up in
xrandr. If the activation of the port is dependent on the monitor being there
then that's not good because I don't want to have to reboot every time I want
the monitor to be detected.

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