Bug 470820

Summary:	sys-kernel/*-sources-3.9, Intel GPU - Intense brightness in HDMI-connected LCD (fb console and X)
Product:	Gentoo Linux	Reporter:	Roman Žilka <roman.zilka>
Component:	[OLD] Core system	Assignee:	Gentoo Kernel Bug Wranglers and Kernel Maintainers <kernel>
Status:	RESOLVED INVALID
Severity:	normal	Keywords:	UPSTREAM
Priority:	Normal
Version:	unspecified
Hardware:	All
OS:	Linux
URL:	https://bugzilla.kernel.org/show_bug.cgi?id=58871
Whiteboard:
Package list:		Runtime testing required:	---
Attachments:	emerge --info .config

Description Roman Žilka 2013-05-20 18:54:26 UTC

Booting kernel 3.9 I get an intense brightness/alpha in the (external) LCD. The problem appears the moment the kernel begins to boot in the (fb) text console and carries over to X as well. Due to config option deps I can't replace the fb console with the classic VGA one. I suppose I could find a way to turn down the brightness in X by a software means, but this is a bug that shouldn't be there.

There is no change in Xorg.0.log when X runs under 3.8 and 3.9. I have an embedded Sandy Bridge Intel GPU.

The LCD is connected to a laptop via HDMI. I can't tell for sure if the brightness has risen in the laptop built-in LCD too - I rarely use it these days - but my guess is that it has risen there too.

Reproducible: Always

Comment 1 Roman Žilka 2013-05-20 18:55:42 UTC

Created attachment 348786 [details]
emerge --info

Comment 2 Roman Žilka 2013-05-20 19:26:50 UTC

Created attachment 348788 [details]
.config

The problem persists even if I remove x2apic support and (almost) everything under ACPI / power mgmt. These are the changes between 3.8.12 and 3.9.3 in the Drivers -> Graphics area:

CONFIG_DRM_TTM=m
CONFIG_DRM_GMA500=m
CONFIG_HDMI=y

Neither of these was present in 3.8. I don't load these modules anyway, though, and CONFIG_HDMI cannot be (un)set manually and is auto-selected by CONFIG_DRM.

Comment 3 Roman Žilka 2013-05-23 11:32:30 UTC

This issue doesn't go away with disabling MAXSMP (bug 470792).

Comment 4 Agostino Sarubbo gentoo-dev

2013-05-26 15:31:42 UTC

@Roman, thanks for the report.

Would be better if the report goes directly to the upstream bugzilla.

Comment 5 Tom Wijsman (TomWij) (RETIRED) gentoo-dev

2013-05-26 15:49:51 UTC

Agreed, please file this at https://bugzilla.kernel.org/ and provide us the link to the upstream bug; thanks in advance.

Comment 6 Roman Žilka 2013-05-27 19:56:24 UTC

Daniel Vetter (upstream) replied:

"
This is intended behaviour, we've implemented the automatic selection of
broadcast rbg support for hdmi according to spec. I know specs are crap and
even more so wrt hdmi screens, but this is about as good as it'll get.

If you're unhappy with the new mode you can override it with the "RBG
Broadcast" xrandr connector property attached to the HDMI output.
"