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    SubjectACPI regression in 2.6.29 - cpufreq_performance doesn't work

    If i set performance for scaling_governor using 2.6.29-rc4-git2,
    ondemand stills control my CPU.
    I get just 800MHz instead of 2268MHz.

    dub:/sys/devices/system/cpu/cpu0/cpufreq# cat cpuinfo_cur_freq
    dub:/sys/devices/system/cpu/cpu0/cpufreq# echo performance > scaling_governor
    dub:/sys/devices/system/cpu/cpu0/cpufreq# cat scaling_governor
    dub:/sys/devices/system/cpu/cpu0/cpufreq# cat cpuinfo_cur_freq

    But, /proc/cpuinfo still shows 800MHz:

    model name : Intel(R) Core(TM)2 Duo CPU P8400 @ 2.26GHz
    stepping : 6
    cpu MHz : 800.000

    And i cannot remove the ondemand module, that is not used anymore:

    dub:/sys/devices/system/cpu/cpu0/cpufreq# rmmod cpufreq_ondemand
    ERROR: Module cpufreq_ondemand is in use

    I can confirm that it's not at 2268MHz because glxgears differs:
    alemao@dub:~/linux-2.6$ glxgears
    4268 frames in 5.0 seconds = 853.428 FPS
    alemao@dub:~/linux-2.6$ sudo cpufreq-set -g ondemand
    alemao@dub:~/linux-2.6$ glxgears
    3283 frames in 5.0 seconds = 656.429 FPS

    With 2.6.29-rc4-git2 and scaling_governor as "performance" i got about ~660FPS.

    I've git bisect from (which was working) to 2.6.29-rc4-git2
    and i get into this:

    alemao@dub:~/linux-2.6$ git bisect good
    d96f94c604453f87fe24154b87e1e9a3a72511f8 is first bad commit
    commit d96f94c604453f87fe24154b87e1e9a3a72511f8
    Author: Pallipadi, Venkatesh <>
    Date: Mon Feb 2 11:57:18 2009 -0800

    ACPI: Enable bit 11 in _PDC to advertise hw coord

    Bit 11 in intel PDC definitions is meant for OS capability to handle
    hardware coordination of P-states. In Linux we have always supported
    hwardware coordination of P-states. Just let the BIOSes know that we
    support it, by setting this bit.

    Some BIOSes use this bit to choose between hardware or software coordination
    and without this change below, BIOSes switch to software coordination, which
    is not very optimal in terms of power consumption and extra
    wakeups from idle.

    Signed-off-by: Venkatesh Pallipadi <>
    Signed-off-by: Len Brown <>

    :040000 040000 bc006c98ae03b69ad27b2e80227abba178326d8d
    e97c37098193793e3e2e719ecdac2fe5eab94104 M include

    Now, without this patch, cpufreq_performance behaves correctly:

    alemao@dub:~/linux-2.6$ uname -a
    Linux dub 2.6.29-rc2 #27 SMP Tue Feb 10 01:36:46 BRST 2009 x86_64 GNU/Linux
    alemao@dub:~/linux-2.6$ cat /proc/cpuinfo | grep MH
    cpu MHz : 2268.000
    cpu MHz : 2268.000
    alemao@dub:~/linux-2.6$ cat


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