Problem with LCD backlight remaining on during ACPI sleep

From ThinkWiki
Revision as of 12:38, 10 May 2005 by (Talk)
Jump to: navigation, search

Problem description

On some models the LCD backlight remains on during ACPI sleep.

Affected Models

(according to the relevant bug on the Kernel bug tracker (bug 2576))

Partial solution

If the ThinkPad has a radeon video chip, then switching off the light with the command

 radeontool light off

will work, but only in a text-mode virtual terminal. If X is running, the light apparently comes back on when the kernel switches to text mode prior to sleeping. The solution in that case it to switch to a text mode console first.

I use the following script to suspend my machine. The hwclock lines compensate for the clock running at double speed during suspend (this is fixed in the 2.6.11 release candidate kernels, various distributions may backport the fix).

logger "Software suspend to ram."
/sbin/hwclock --systohc
chvt 1
radeontool light off
echo -n 3 >/proc/acpi/sleep
/sbin/hwclock --adjust
/sbin/hwclock --hctosys
logger "Woke up from suspend."
radeontool light on

Improvements are clearly possible. :-)