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<base href="https://bugs.freedesktop.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [NVAC] iMac9,1 effective backlight brightness range changes after S3"
href="https://bugs.freedesktop.org/show_bug.cgi?id=98677">98677</a>
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<th>Summary</th>
<td>[NVAC] iMac9,1 effective backlight brightness range changes after S3
</td>
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<th>Product</th>
<td>xorg
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>x86-64 (AMD64)
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<th>OS</th>
<td>Linux (All)
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>medium
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<th>Component</th>
<td>Driver/nouveau
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<th>Assignee</th>
<td>nouveau@lists.freedesktop.org
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<th>Reporter</th>
<td>jefferym@gmail.com
</td>
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<th>QA Contact</th>
<td>xorg-team@lists.x.org
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<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=127900" name="attach_127900" title="dmesg output after the resume with some nouveau trace options">attachment 127900</a> <a href="attachment.cgi?id=127900&action=edit" title="dmesg output after the resume with some nouveau trace options">[details]</a></span>
dmesg output after the resume with some nouveau trace options
I have an iMac 9,1 where the behaviour of the backlight of the built in screen
works differently between the first boot and after a suspend to ram.
It appears to be darker at lower values before a suspend than after.
kernel: 4.8.6-300.fc25.x86_64
lspci adapter: VGA adapter NVIDIA Corporation C79 [GeForce 9400] [10de:0867]
DMI: Apple Inc. iMac9,1/Mac-F2218EA9
I've been booting in EFI mode.
I do not know of a regression. I've only tried 4.4 and this 4.8 kernels.
I've observed this with X running but I've been testing this without starting a
graphical environment.
I've been testing by setting setting backlight values via the
/sys/backlight/nv_backlight/brightness interface.
Before a suspend I can set values such as 40, 70, 100 and the brightness seems
to be reasonable on the screen.
I then suspend to ram via the /sys/power/state interface.
Upon resuming the backlight appears to be at 100 percent. If I set the
brightness to values such as 30 and 60 the screen remains dark. It is barely
visible as a flicker at 70. At 100 it is visible.
I've observed that the value of NV50_PDISP_SOR_PWM_DIV (0x0061c080) is 0x1
after a boot but is set to 0x84 after a resume.
It appears there's an init script in the bios dump which sets it to the value
of 0x84. I have confirmed if I use the nouveau option
nouveau.config=NvForcePost=1 that the behavior after booting is the same as
after a resume. The value of 0x61c080 is 0x84.
If I `nvapoke 0x061c080 0x1` after a resume the backlight seems to work fairly
well. I created patch to test this. I expect it isn't the proper solution.
I'm attaching the dmesg which includes a resume with the nouveau driver.
I'll also attach the vbios dump, acpidump, dmidecode, lspci,
I've gathered an mmiotrace of the binary driver as it sets a few brightness
values as well.</pre>
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