linux-kernel - Re: i915 black screen introduced by ACPI changes

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Date:	Mon, 4 Mar 2013 15:33:50 -0800
From:	Chris Li <lkml@...isli.org>
To:	Daniel Vetter <daniel.vetter@...ll.ch>
Cc:	Jesse Barnes <jbarnes@...tuousgeek.org>,
	linux-kernel@...r.kernel.org, robert.moore@...el.com,
	feng.tang@...el.com, len.brown@...el.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	intel-gfx <intel-gfx@...ts.freedesktop.org>
Subject: Re: i915 black screen introduced by ACPI changes

On Mon, Mar 4, 2013 at 3:16 PM, Chris Li <lkml@...isli.org> wrote:
>>> Two things to test:
>>> - Can you please check whether any of the backlight drivers in
>>> /sys/class/backlight does anything? You need to frob the brightness
>>> file. Please also list all the drivers you have.

This is the kernel with the ACPI change causing the black screen.

lrwxrwxrwx. 1 root root 0 Mar  4 15:20 acpi_video0 ->
../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/backlight/acpi_video0
lrwxrwxrwx. 1 root root 0 Mar  4 15:20 acpi_video1 ->
../../devices/pci0000:00/0000:00:02.0/backlight/acpi_video1
lrwxrwxrwx. 1 root root 0 Mar  4 15:20 intel_backlight ->
../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight

Here is the interesting part. The brightness and max_brightness is all
set to 4648,
However, the actual brightness is 0. The bl_power is also 0. I think
you are on to some thing.

I attach the reg dump as intel-reg-bad.

Chris

Download attachment "intel-reg-bad" of type "application/octet-stream" (14955 bytes)