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    Subjectcpufreq terminally broken [was Re: community PM requirements/issues and PowerOP]
    Hi!

    Just for the record... this goes out to the lkml. This discussion was
    internal for way too long. (for interested lkml readers, I'm sure
    linux-pm mailing list has public archive somewhere).

    On Tue 2006-09-12 02:05:26, Eugeny S. Mints wrote:
    > Pavel Machek wrote:
    > >>>>- PowerOP is only one layer (towards the bottom) in a power management
    > >>>>solution.
    > >>>>- PowerOP does *not* replace cpufreq
    > >>>PowerOP provides userland interface for changing processor
    > >>>frequency. That's bad -- duplicate interface.
    > >>Basically the biggest problem with cpufreq interface is that cpufreq has
    > >>"chose
    > >>predefined closest to a given frequency" functionality implemented in the
    > >>kernel while there is _no_ any reason to have this functionality
    > >>implemented in
    > >>the kernel if we have sysfs interface exported by PowerOP in place - you
    > >>just
    > >
    > >No, there is reason to keep that in kernel -- so that cpufreq
    > >userspace interface can be kept, and so that resulting kernel<->user
    > >interface is not ugly.
    > Cpuferq defines cpufreq_frequency_table structure in arch independent
    > header while it's arch dependent data structure. A lot of code is built
    > around this invalid basic brick and therefore is invalid: cpufreq tables,
    > interface with cpu freq drivers, etc. Notion of transition latency as it
    > defined by cpufreq is wrong because it's not a function of cpu type but
    > function of current and next operating point. no runtime control on
    > operating points set. it's always the same set of operating points for all
    > system cpus in smp case and no way to define different sets or track any
    > dependencies in case say multi core cpus. insufficient kernel<->user space
    > interface to handle embedded requirements and no way to extend it within
    > current design. Shall I continue? Why should then anyone want to keep
    > cpufreq userspace interface just due to keep it?

    Yes, please continue. I do not think we can just rip cpufreq interface
    out of kernel, and I do not think it is as broken as you claim it
    is. Ripping interface out of kernel takes years.

    I'm sure cpufreq_frequency_table could be moved to asm/ header if you
    felt strongly about that.

    I believe we need to fix cpufreq if it is broken for embedded
    cases.
    Pavel
    --
    (english) http://www.livejournal.com/~pavelmachek
    (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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