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    SubjectRe: [patch] prefer TSC over PM Timer
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    On Mon, 2004-11-15 at 19:21 -0800, dean gaudet wrote:
    > On Mon, 15 Nov 2004, john stultz wrote:
    > > With your patch, ACPI PM would never be selected (as TSC always wins
    > > when available, and it will be available on all ACPI enabled i386
    > > systems). So its just the same as disabling CONFIG_X86_PM_TIMER, so why
    > > not just do that?
    >
    > my patch lets you use "clock=pmtmr" if you want it.

    Yea, but at that point you have to enable it in the config and then pass
    a boot parameter to use it. I dunno. If you want to go with that you
    should def include a comment in the pmtmr code as well as in the config
    help.

    > > Do note, using the "clock=tsc" boot option, you can easily force the
    > > system to use the TSC.
    >
    > right -- except i think the default is the opposite of what it should be
    > for a generic kernel. i think more systems are served better by using tsc
    > than those that need clock=pm... NUMA systems are rare (with custom
    > kernels/etc), and if my experience with the centrino is valid then newer
    > laptops aren't having this tsc/cpufreq problem.
    >
    > > I would however, support a patch that selected the TSC over the ACPI PM
    > > time source when CONFIG_CPUFREQ and CONFIG_SMP were N. That's fairly
    > > safe.
    >
    > i'm looking for a solution that generic distribution kernels can use...
    >
    > honestly my selfish motivation is to get efficeon/crusoe treated properly
    > -- they support a fixed TSC rate which does not vary with frequency (which
    > many people fault us for, but the reality is that fixed TSC is the only
    > viable solution for a processor which can vary power consumption without
    > the involvement of the kernel).

    Yea, I just wish we could get away from the TSC and have a well defined
    and hardware guaranteed timebase register like PPC.

    > i'd advocate a patch like the one
    > below... but it feels wrong.

    Yea, no, I definitely don't like that. I know how these tricks work,
    send out a worse patch to make the first look better ;) But alas, you've
    worn me down! Add the comments I mentioned above and I'd go along with
    it.

    Dominik: are you cool with this?

    thanks
    -john

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