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<th>Priority</th>
<td>medium
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Brightness control becomes binary after suspend on haswell"
href="https://bugs.freedesktop.org/show_bug.cgi?id=72976">72976</a>
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<th>Assignee</th>
<td>chris@chris-wilson.co.uk
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<th>Summary</th>
<td>Brightness control becomes binary after suspend on haswell
</td>
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<th>QA Contact</th>
<td>intel-gfx-bugs@lists.freedesktop.org
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Classification</th>
<td>Unclassified
</td>
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<th>OS</th>
<td>All
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<th>Reporter</th>
<td>lionel.g.landwerlin@linux.intel.com
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<th>Hardware</th>
<td>Other
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Component</th>
<td>Driver/intel
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<th>Product</th>
<td>xorg
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<pre>I'm using Linux on my macbook air 2013 (haswell) (using Debian).
After a suspend cycle, the brightness will just go binary, full brightness for
the 91-100%, and then completely blank under 91%.
I've noticed the behavior while using Gnome, then tried to reproduce
by poking at
/sys/devices/pci0000:00/0000:00:02.0/backlight/acpi_video0/brightness directly.
Then I tried poking at
/sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/intel_backlight/brightness
where the range is 0-2777. And I found the same kind of behavior, except that
at the values 2303/2304, the screen would just keep going up/down in brightness
without any interection on the /sys interface. Otherwise 2302 and below would
be blank and 2305 and above would be full brightness
It's using the following relevant components :
xserver-xorg 7.7+4
xserver-xorg-video-intel 2.21.15-1+b2
kernel 3.12.3
I guess the bug is more likely to be somewhere in the kernel than in the X
driver.
Folks have reported the bug in other places already :
<a href="https://bugzilla.redhat.com/show_bug.cgi?id=989555">https://bugzilla.redhat.com/show_bug.cgi?id=989555</a>
<a href="https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1197482">https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1197482</a></pre>
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