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<base href="https://bugs.freedesktop.org/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Priority</th>
<td>medium
</td>
</tr>
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [ivb regression] 3.10: i915 blanks eDP panel (backlight set to 0 and further ineffective)"
href="https://bugs.freedesktop.org/show_bug.cgi?id=67950">67950</a>
</td>
</tr>
<tr>
<th>CC</th>
<td>kirill@shutemov.name, vsu@altlinux.org
</td>
</tr>
<tr>
<th>Assignee</th>
<td>intel-gfx-bugs@lists.freedesktop.org
</td>
</tr>
<tr>
<th>Summary</th>
<td>[ivb regression] 3.10: i915 blanks eDP panel (backlight set to 0 and further ineffective)
</td>
</tr>
<tr>
<th>QA Contact</th>
<td>intel-gfx-bugs@lists.freedesktop.org
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr>
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<th>OS</th>
<td>Linux (All)
</td>
</tr>
<tr>
<th>Reporter</th>
<td>mike@altlinux.org
</td>
</tr>
<tr>
<th>URL</th>
<td>https://bugzilla.altlinux.org/29219
</td>
</tr>
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<th>Hardware</th>
<td>x86-64 (AMD64)
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Version</th>
<td>XOrg CVS
</td>
</tr>
<tr>
<th>Component</th>
<td>DRM/Intel
</td>
</tr>
<tr>
<th>Product</th>
<td>DRI
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=83890" name="attach_83890" title="dmesg from UX31A running under 3.10.5 with drm.debug=0xe">attachment 83890</a> <a href="attachment.cgi?id=83890&action=edit" title="dmesg from UX31A running under 3.10.5 with drm.debug=0xe">[details]</a></span>
dmesg from UX31A running under 3.10.5 with drm.debug=0xe
This has been reported in ALT Linux bugzilla (in Russian), posting here at
Kirill's request as I've confirmed a report by another user on the same
hardware I happen to use.
3.10.x kernels up to and including 3.10.5 result in turning off the backlight
at i915 module load time on ASUS UX31A (i7-3517U); dmesg with drm.debug=0xe and
late module load (not in initrd) is attached; external VGA monitor works fine
(dmesg and Xorg.1.log available if needed).
Here's a transcript of sysfs knob fiddling over ssh:
root@ux class/backlight/intel_backlight # cat actual_brightness
0
root@ux class/backlight/intel_backlight # cat max_brightness
4302
root@ux class/backlight/intel_backlight # echo 800 > brightness
root@ux class/backlight/intel_backlight # cat actual_brightness
4302
and corresponding bits of dmesg (including further attempts at putting 100 and
80 values into brightness; both resulted in actual_brightness reading the same
values but the screen backlight is still off):
[ 877.052934] [drm:intel_panel_actually_set_backlight], set backlight PWM =
4302
[ 881.868818] [drm:intel_panel_get_backlight], get backlight PWM = 4302
[ 974.670199] [drm:intel_panel_get_backlight], get backlight PWM = 4302
[ 978.469350] [drm:intel_panel_actually_set_backlight], set backlight PWM =
100
[ 981.176898] [drm:intel_panel_get_backlight], get backlight PWM = 100
[ 990.186065] [drm:intel_panel_actually_set_backlight], set backlight PWM = 80
acpi_video0 doesn't have any effect either.
This bug hasn't manifested itself on 3.9.7 with very similar configuration on
the same hardware.
I've skimmed over <a class="bz_bug_link
bz_status_VERIFIED bz_closed"
title="VERIFIED FIXED - [Regression IVB cpu eDP] eDP shows uncorrectly backlight after booting"
href="show_bug.cgi?id=51394">bug #51394</a> and <a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [845g regression] pipe A assertion failure (expected on, current off)"
href="show_bug.cgi?id=66462">bug #66462</a> which might be related; #54687 and
#65652 seem rather not.</pre>
</div>
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