Distro: SLED11 SP1 Kernel: 2.6.38-rc5 Platform: Intel Montevina with GM45 Integrated Graphics Rate: 100% A resolution change will induce unexpected brightness change, especially when you change from high to low then back to high. For better understanding, the script used to reproduce it is provided. #!/bin/bash CNT=10 while (( CNT-- > 0 )); do xrandr --output LVDS1 --mode 800x600 xrandr --output LVDS1 --mode 1366x768 done You will end with a dimmest brightness level in 1366x768. Also each iteration would dim brightness level by 1.
Could you test with upstream linux-2.6 git with below commit? commit 951f3512dba5bd44cda3e5ee22b4b522e4bb09fb Author: Indan Zupancic <indan@nul.nu> Date: Thu Feb 17 02:41:49 2011 +0100 drm/i915: Do not handle backlight combination mode specially
(In reply to comment #1) > Could you test with upstream linux-2.6 git with below commit? > > commit 951f3512dba5bd44cda3e5ee22b4b522e4bb09fb > Author: Indan Zupancic <indan@nul.nu> > Date: Thu Feb 17 02:41:49 2011 +0100 > > drm/i915: Do not handle backlight combination mode specially That patch made it upstream, it's in rc6 now.
This morning I tested a patch from Takashi that fixed the issue. ----------- From f6b8a45b9544072e6ddbb944a4c03a9ec8cbca3a Mon Sep 17 00:00:00 2001 From: Takashi Iwai <tiwai@suse.de> Date: Mon, 21 Feb 2011 14:19:27 +0100 Subject: [PATCH] drm/i915: Fix calculation of backlight value in combined mode The commit a95735569312f2ab0c80425e2cd1e5cb0b4e1870 drm/i915: Refactor panel backlight controls causes a regression for GM45 that is using the combined mode for controlling the backlight brightness. The commit introduced a wrong bit shift for computing the current backlight level. Bugzilla: https://bugzilla.novell.com/show_bug.cgi?id=672946 Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=34524 Signed-off-by: Takashi Iwai <tiwai@suse.de> Cc: <stable@kernel.org> --- drivers/gpu/drm/i915/intel_panel.c | 1 - 1 file changed, 1 deletion(-) --- a/drivers/gpu/drm/i915/intel_panel.c +++ b/drivers/gpu/drm/i915/intel_panel.c @@ -176,7 +176,6 @@ val &= ~1; pci_read_config_byte(dev->pdev, PCI_LBPC, &lbpc); val *= lbpc; - val >>= 1; } } ----------- Therefore, a quick glance of the upstream patch should work, because we know it is wrong backlight calculation in combination mode made the trouble. I will try this patch and update it later. Many thanks for every kernel experts' help. :)
(In reply to comment #2) > (In reply to comment #1) > > Could you test with upstream linux-2.6 git with below commit? > > > > commit 951f3512dba5bd44cda3e5ee22b4b522e4bb09fb > > Author: Indan Zupancic <indan@nul.nu> > > Date: Thu Feb 17 02:41:49 2011 +0100 > > > > drm/i915: Do not handle backlight combination mode specially > > That patch made it upstream, it's in rc6 now. Verified fixed in 2.6.38-rc6. Thanks.
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