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    SubjectRe: [PATCH 3/4] new timeofday x86-64 arch specific changes (v. B1)
    Possibly the code could auto-detect the brokenness during initialization by 
    executing inl(pmtmr_ioport) a few hundred times and watch for monotony.

    Regards,
    Ulrich


    On 2 Jun 2005 at 19:50, Parag Warudkar wrote:

    > On Thursday 02 June 2005 19:20, john stultz wrote:
    > > Could you see if the slowness you're feeling is correlated to the
    > > acpi_pm timesource?
    >
    > Speaking of which, the below code from arch/i386/timer_pm.c looks particularly
    > more taxing to me - 3 times read from ioport in a loop - not sure how many
    > time that executes.
    >
    > static inline u32 read_pmtmr(void)
    > {
    > u32 v1=0,v2=0,v3=0;
    > /* It has been reported that because of various broken
    > * chipsets (ICH4, PIIX4 and PIIX4E) where the ACPI PM time
    > * source is not latched, so you must read it multiple
    > * times to insure a safe value is read.
    > */
    > do {
    > v1 = inl(pmtmr_ioport);
    > v2 = inl(pmtmr_ioport);
    > v3 = inl(pmtmr_ioport);
    > } while ((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1)
    > || (v3 > v1 && v3 < v2));
    >
    > Shouldn't that loop be limited to the broken chipsets - why would correct
    > people with correctly working chipsets carry this extra burden? (Or is it
    > insignificant?)
    >
    > --
    > Because we don't think about future generations, they will never forget us.
    > -- Henrik Tikkanen


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