I have MSI Wind U100 netbook (945GM chipset). After upgrading driver to 2.9.x DPMS stopped working in xorg: screen just blinks and stays in "on" state. I've found that this problem is caused by driver setting brightness to 0 when setting DPMS level (src/drmmode_display.c:925) via kernel backlight driver. And on my system writing to /sys/devices/backlight/acpi_video0/brightness generates keypress events (as if I pressed brightness controls on keyboard). This keypresses immediately wake x server. Simplest fix is to remove drmmode_output_dpms_backlight call. Actually, I'm not sure if this "feature" should be filed here. Maybe this should be corrected in kernel. But it seems it is easier to correct in xorg driver. BTW, in non-KMS mode this problem also exists but can be easily repaired by setting BACKLIGHT_CONTROL to 'native' with xrandr. Kernel version: 2.6.31 Xorg version: 1.7.1 Intel driver version: 2.9.1
I'll assign this to Jesse. I'm guessing that he'll know the proper fix, (or at least know the person who should know that). -Carl
A few more details on this can be found on the Ubuntu bugtracker: https://bugs.launchpad.net/xserver-xorg-video-intel/+bug/453812
Does this still happen with 2.6.33-rc kernels and the 2.10 X driver?
Hi, Alex Sorry for the late response. Do you try to remove the remove drmmode_output_dpms_backlight call in drmmode_output_dpms and see whether the issue can be fixed? It seems that we use the incorrect order to set the backlight brightness. When the LVDS enters the DPMS off set, we will use the kernel syscall to put it into DPMS off set and then read the backlight brightness setting(In fact it will be the lowest). When we put it into DPMS on state again, it will then use the kernel syscall and then restore the saved backlight brightness setting. It is incorrect. Please check whether it can work for you if you remove the drmmode_output_dpms_backlight call in drmmode_output_dpms. thanks. Yakui
Hi, I am currently not using latest kernel - mine is 2.6.32 (with gentoo patchset). Intel driver is quite up-to-date - 2.10.0. To make DPMS work, I've commented "drmmode_output_dpms_backlight" call in drmmode_output_dpms. So yes, commenting drmmode_output_dpms_backlight works.
HI, Alex Can you send the corresponding patch to intel-gfx mailing list? And then I can add the "Acked-by". thanks. Yakui
Let's not hold here. Yakui, could you send/commit the patch if Alex doesn't do that?
On my MSI Wind U100 I cannot reproduce this any more after upgrading the BIOS to version 1.0G.
I've just upgraded BIOS to 1.0g on my U100 and can confirm: this bug dissapeared.
Removing drmmode_output_dpms_backlight is certainly not the right solution. As long as there is a BIOS update that fixes this issue I'd suggest to not change that part of code. It's especially prone to break power saving for older laptop models that don't have dedicated hardware for switching off the backlight if the panel doesn't get a valid signal.
I agree with Matthias. Apparently that's a BIOS bug. Hence closing accordingly.
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