On Fri, Jun 03, 2005 at 08:24:35AM -0700, john stultz wrote:
> On Thu, 2005-06-02 at 19:50 -0400, 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?)
>
> Yea, that would be nice to only do the triple read on the affected
> systems. Although outside of the comment I don't have any real data as
> to which system suffer from the issue.
IIRC (from the comment above) several chipsets suffer from this
inconsistency, namely the widely used PIIX4(E) and ICH(4 only? or also other
ICH-ones?). Therefore, we'd need at least some sort of boot-time check to
decide which method to use... and based on the method, we can adjust the
priority maybe?
Thanks,
Dominik
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
