[issue1359] PowerNow! support

[Matthew Dillon]

:Alexander Polakov <polachok at gmail.com> added the comment:
:
:Hi there again.
:
:I tried to add some code for pstates into acpi_cpu and changed powernow dri=
:ver
:to use them. Any review?

    The code looks very clean.  It detects "Cool'n Quiet" on my AMD
    test box, and it seems to work.  I can set the frequency to
    1000, 1800, or 2000.  However, when I load the module it seems
    to default to the lowest frequency.

    test28# /tmp/loop2
    SMP contention, userland-only loop, duel-forks.  Run just one
    loop2/2xfork  0.361s 1000000 loops =  0.361uS/loop

    test28# kldload powernow
    test28# /tmp/loop2
    SMP contention, userland-only loop, duel-forks.  Run just one
    loop2/2xfork  0.725s 1000000 loops =  0.725uS/loop

    test28# sysctl machdep.powernow
    machdep.powernow.frequency.target: 1000
    machdep.powernow.frequency.current: 1000
    machdep.powernow.frequency.available: 2000 1800 1000

    test28# sysctl machdep.powernow.target=2000
    test28# /tmp/loop2
    SMP contention, userland-only loop, duel-forks.  Run just one
    loop2/2xfork  0.361s 1000000 loops =  0.361uS/loop

    The only issue I see is that the frequency on module load is
    being set to the lowest value.  It should probably retain whatever
    the existing frequency is (if possible).

						-Matt