Bug 94813 - [VLV, backlight] Backlight Brighness not linear
Summary: [VLV, backlight] Backlight Brighness not linear
Status: CLOSED FIXED
Alias: None
Product: DRI
Classification: Unclassified
Component: DRM/Intel (show other bugs)
Version: unspecified
Hardware: x86-64 (AMD64) Linux (All)
: medium normal
Assignee: Intel GFX Bugs mailing list
QA Contact: Intel GFX Bugs mailing list
URL:
Whiteboard:
Keywords:
Depends on:
Blocks:
 
Reported: 2016-04-04 12:03 UTC by Egbert Eich
Modified: 2017-04-11 13:10 UTC (History)
2 users (show)

See Also:
i915 platform: BYT
i915 features: display/backlight


Attachments
kernel log w drm.debug=0x6 (100.36 KB, text/plain)
2016-04-04 12:03 UTC, Egbert Eich
no flags Details

Description Egbert Eich 2016-04-04 12:03:47 UTC
Created attachment 122698 [details]
kernel log w drm.debug=0x6

We've received a report that the backlight brightness behaves non-linear on a VLV 
(PCI DevID: 0x0f31) with kernel 4.5 or any eariler kernel. Driver seems to use the vlv_*_backlight() functions.

The brightness range is: 0 - 7812. 
Written to /sys/class/backlight/intel_backlight/brignness 0 and 7812 give black, 1 and 4687 both give full brightness.
Comment 1 yann 2017-03-17 15:26:47 UTC
(In reply to Egbert Eich from comment #0)
> Created attachment 122698 [details]
> kernel log w drm.debug=0x6
> 
> We've received a report that the backlight brightness behaves non-linear on
> a VLV 
> (PCI DevID: 0x0f31) with kernel 4.5 or any eariler kernel. Driver seems to
> use the vlv_*_backlight() functions.
> 
> The brightness range is: 0 - 7812. 
> Written to /sys/class/backlight/intel_backlight/brignness 0 and 7812 give
> black, 1 and 4687 both give full brightness.

We seem to have neglected the bug a bit, apologies.

Egbert Eich, since There were improvements pushed in kernel that will benefit to your system, so please re-test with latest kernel and mark as REOPENED if you can reproduce (and attach fresh gpu error dump & kernel log) and RESOLVED/* if you cannot reproduce.
Comment 2 yann 2017-04-11 13:10:43 UTC
(In reply to yann from comment #1)
> (In reply to Egbert Eich from comment #0)
> > Created attachment 122698 [details]
> > kernel log w drm.debug=0x6
> > 
> > We've received a report that the backlight brightness behaves non-linear on
> > a VLV 
> > (PCI DevID: 0x0f31) with kernel 4.5 or any eariler kernel. Driver seems to
> > use the vlv_*_backlight() functions.
> > 
> > The brightness range is: 0 - 7812. 
> > Written to /sys/class/backlight/intel_backlight/brignness 0 and 7812 give
> > black, 1 and 4687 both give full brightness.
> 
> We seem to have neglected the bug a bit, apologies.
> 
> Egbert Eich, since There were improvements pushed in kernel that will
> benefit to your system, so please re-test with latest kernel and mark as
> REOPENED if you can reproduce (and attach fresh gpu error dump & kernel log)
> and RESOLVED/* if you cannot reproduce.

Timeout - assuming resolved+fixed.

If problem still persist with the latest kernels (preferable drm-tip from git://anongit.freedesktop.org/git/drm-tip), reopen this bug with latest logs as attachments.


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