Bug 63791

Summary: Display too bright, DVI output, Intel Haswell graphics
Product: Drivers Reporter: Mike (pmike2001)
Component: Video(DRI - Intel)Assignee: intel-gfx-bugs (intel-gfx-bugs)
Status: RESOLVED WILL_NOT_FIX    
Severity: normal CC: daniel, intel-gfx-bugs
Priority: P1    
Hardware: x86-64   
OS: Linux   
Kernel Version: 3.11.0-13-generic #20~precise2-Ubuntu Subsystem:
Regression: No Bisected commit-id:
Attachments: dmesg with drm.debug=0xe
acpidump
lspci -vvv

Description Mike 2013-10-26 16:36:21 UTC
Created attachment 112311 [details]
dmesg with drm.debug=0xe

I've upgraded kernel from 3.8.0-33 to 3.11.0-13 (Ubuntu-baked kernels), and display brightness increased significantly. It's possible to modify gamma, but it doesn't affect *brightness* (or maybe backlight level).

My HW is: Intel Core i5-4570S CPU build-in graphics, connected to flat-panel monitor via DVI-to-HDMI cable.

PS. acpi_backlight=vendor does not have any effect.
PPS. 3.12-rcX kernels have same issue.
Comment 1 Mike 2013-10-26 16:37:53 UTC
Created attachment 112321 [details]
acpidump
Comment 2 Mike 2013-10-26 16:38:32 UTC
Created attachment 112331 [details]
lspci -vvv
Comment 3 Daniel Vetter 2013-10-27 18:19:10 UTC
Unfortunately this is a wontfix one. We've adjusted the limited rbg range handling a bit to be more standards compliant, but unfortunately that breaks all the less standards compliant screens.

You can work around this with

xrandr -output HDMI1 --set "Broadcast RGB" Full

Thanks for reporting this anyway and please reopen if the w/a doesn't help.
Comment 4 Mike 2013-10-28 06:02:35 UTC
Hi Daniel, indeed my monitor has "incomplete" 6-bit IPS matrix, so it might appears by 2-bits "brighter".

However, your xrandr "magic" workaround works, thanks!
I think this should be documented somewhere, since working with overbrighted display is uncomfortable, and no other workaround exists.

PS. Missing "-" fixed:
xrandr --output HDMI1 --set "Broadcast RGB" Full