Problem with LCD backlight remaining on during ACPI sleep

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Revision as of 19:49, 27 December 2005 by 206.169.194.147 (Talk) (→‎Partial solution)
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Problem description

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

Affected Models

  • ThinkPad 390X with kernel boot option ACPI=force
  • ThinkPad A30
  • ThinkPad A31p
  • ThinkPad T30
  • ThinkPad X31,X32
  • ThinkPad R51

(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. 

logger "Software suspend to ram."
FGCONSOLE=`fgconsole`
chvt 1
radeontool light off
echo -n 3 >/proc/acpi/sleep
logger "Woke up from suspend."
radeontool light on
chvt $FGCONSOLE

Improvements are clearly possible. :-)

On the X32, at least, the bios will switch off the screen by default on a lid close, and suspending to ram interrupts this, and the screen will turn back on. This can be fixed by simply adding "sleep 5" before "echo -n 3 > /proc/acpi/sleep". The suspend will take longer, but the screen will remain off.

A similar script can be found on the acpid configuration HOWTO page.

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