Radeon drm: dpms backlight problem / question / bug?

Michel Dänzer michel at daenzer.net
Tue Nov 2 00:20:52 PDT 2010

On Mon, 2010-11-01 at 16:09 +0100, Prof. Dr. Klaus Kusche wrote: 
> On my Dell Precision M6500, backlight power switching does not work,
> neither by using bl_power in /sys/backlight/...

Please provide the full path of the file you're using.

> nor by using DPMS:
> * Any changes of bl_power are simply and silently ignored
>    (no effect, except that brightness is set to minimum),
>    although brightness tuning works fine
>    (in other words: Both the generic ACPI BIOS driver and the in-kernel
>    Dell laptop backlight driver can control backlight brightness,
>    but not backlight power).
> * If DPMS becomes active, the screen contents on the internal display
>    slowly becomes garbled or fades away (so video output drivers
>    seem to be off), but the backlight remains on
>    (which is very bad for battery power).
>    The external screen (on display port) behaves even worse:
>    It enters energy saving mode (backlight off) and immediately wakes up
>    again, continuously cycling the backlight power every few seconds.
> Another problem which optically looks the same:
> Zapping the X server (Xorg 1.9.1, radeon 6.13.2) with Ctrl-Alt-Bksp
> leaves the system in an undefined state:
> * Similar to DPMS, the display fades away or gets garbled
>    (video output off), but the backlight remains on.
> * It does not switch to the text console automatically,
>    nor is it possible to switch manually with Ctrl-Alt-Fn.
> Configuration:
> * Kernel
> * Radeon DRM with KMS
> * Radeon framebuffer with backlight control enabled
> * The Radeon chip is a JUNIPER 0x1002:0x68A0,
>    the kernel should contain all the microcode needed for it.

Please provide the full Xorg.0.log file and dmesg output.

Earthling Michel Dänzer           |                http://www.vmware.com
Libre software enthusiast         |          Debian, X and DRI developer

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