Bug 112139

Summary: Using Modesetting and Intel GVT, brightness control becomes slow
Product: DRI Reporter: leozinho29_eu
Component: DRM/iGVT-gAssignee: Terrence Xu <terrence.xu>
Status: RESOLVED MOVED QA Contact: Terrence Xu <terrence.xu>
Severity: not set    
Priority: not set    
Version: unspecified   
Hardware: Other   
OS: All   
Whiteboard:
i915 platform: i915 features:

Description leozinho29_eu 2019-10-26 19:54:15 UTC 
When using modesetting Xorg driver together with Intel GVT (i915.enable_gvt=1), the brightness control on my notebook becomes extremely slow.

The slowness can happen either when pressing the brightness buttons or when using xfce4-power-manager to configure brightness, it seems it has to wait one second for every brightness change. However, if I try to write directly to /sys/class/backlight/intel_backlight/brightness there is no delay. Even something as:

sudo bash -c "while true ; do echo 200 > /sys/class/backlight/intel_backlight/brightness ; sleep 0.05 ; echo 60 > /sys/class/backlight/intel_backlight/brightness ; sleep 0.05 ; done"

changes the brightness very quickly, working with no problems.

When using intel Xorg driver this problem is not present. When disabling Intel GVT the problem does not appear too. It is only present when combining modesetting Xorg driver and Intel GVT.

System specifications:

Computer model: Lenovo Ideapad 310-14ISK;
Processor: Intel Core i3-6100U;
Video: Intel HD Graphics 520;
Architecture: amd64;
Mesa: 19.3.0-devel (git-83a346cd58);
Kernel version: drm-tip (58747eccea0669678be9cd532f778501024d0556);
Distribution: Xubuntu 18.04.3 amd64.
Comment 1 Martin Peres 2019-11-29 16:48:24 UTC 
-- GitLab Migration Automatic Message --

This bug has been migrated to freedesktop.org's GitLab instance and has been closed from further activity.

You can subscribe and participate further through the new bug through this link to our GitLab instance: https://gitlab.freedesktop.org/drm/intel/issues/17.

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