[ltp] Power drain workaround with radeonfb module?

[Felix E. Klee]

On Thinkwiki it's stated [1] that doing "modprobe radeonfb" before
starting X can solve the high power drain issue on certain Thinkpads.

Can that work? I previously thought that radeonfb has to be built into
the kernel, and that's what a recent test confirms with Ubuntu 7.10
(Gutsy Gibbon) on a T41 (2373-3kg):

1. The system started up in text mode (no X).

2. I loaded the module:

  # modprobe radeonfb
  # dmesg
    [...]
    [  932.232000] radeonfb: Monitor 1 type LCD found
    [  932.232000] radeonfb: Monitor 2 type CRT found
    [  932.232000] radeonfb: panel ID string: 1024x768                
    [  932.232000] radeonfb: detected LVDS panel size from BIOS:
    1024x768
    [  932.232000] radeondb: BIOS provided dividers will be used
    [  932.352000] radeonfb: Dynamic Clock Power Management enabled
    [  932.352000] radeonfb: IBM Thinkpad R50/R51/T40/T41 detected,
    enabling workaround
    [  932.352000] radeonfb (0000:01:00.0): ATI Radeon Lf 

3. I executed sleep.sh, from Thinkwiki [2]:

  # ./sleep.sh; reboot
  [...]
  # tail /var/log/battery.log
    [...]
    Sun Oct 28 14:27:16 CET 2007
    before: 12150 mWh
    after: 11200 mWh
    diff: -950 mWh
    seconds: 3023 sec
    result: -1131 mW
    Your model seems to be affected.

On the same hardware, with Slackware 10.2 and a 2.16.14.4 kernel with
radeonfb built in, the power drain issue is solved.

[1]
http://www.thinkwiki.org/wiki/Problem_with_high_power_drain_in_ACPI_sleep

[2] http://www.thinkwiki.org/wiki/ACPI_sleep_power_drain_test_script
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Felix E. Klee
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