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SubjectRe: [patch 43/69] i386: HPET, check if the counter works
ugh... do not send email before breakfast.  do not send email before 
breakfast. nevermind :)

-dean

On Tue, 5 Jun 2007, dean gaudet wrote:

> the HPET specification allows for HPETs with *much* lower resolution than
> 50us. in fact Fmin is 10Hz iirc. (sorry to jump in so late, but i'm
> about a month behind on the list.)
>
> -dean
>
> On Mon, 21 May 2007, Chris Wright wrote:
>
> > -stable review patch. If anyone has any objections, please let us know.
> > ---------------------
> >
> > From: Thomas Gleixner <tglx@linutronix.de>
> >
> > Some systems have a HPET which is not incrementing, which leads to a
> > complete hang. Detect it during HPET setup.
> >
> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> > Signed-off-by: Chris Wright <chrisw@sous-sol.org>
> > ---
> > [chrisw: Why is this not upstream yet?]
> >
> > ---
> > arch/i386/kernel/hpet.c | 24 +++++++++++++++++++++++-
> > 1 file changed, 23 insertions(+), 1 deletion(-)
> >
> > --- linux-2.6.21.1.orig/arch/i386/kernel/hpet.c
> > +++ linux-2.6.21.1/arch/i386/kernel/hpet.c
> > @@ -226,7 +226,8 @@ int __init hpet_enable(void)
> > {
> > unsigned long id;
> > uint64_t hpet_freq;
> > - u64 tmp;
> > + u64 tmp, start, now;
> > + cycle_t t1;
> >
> > if (!is_hpet_capable())
> > return 0;
> > @@ -273,6 +274,27 @@ int __init hpet_enable(void)
> > /* Start the counter */
> > hpet_start_counter();
> >
> > + /* Verify whether hpet counter works */
> > + t1 = read_hpet();
> > + rdtscll(start);
> > +
> > + /*
> > + * We don't know the TSC frequency yet, but waiting for
> > + * 200000 TSC cycles is safe:
> > + * 4 GHz == 50us
> > + * 1 GHz == 200us
> > + */
> > + do {
> > + rep_nop();
> > + rdtscll(now);
> > + } while ((now - start) < 200000UL);
> > +
> > + if (t1 == read_hpet()) {
> > + printk(KERN_WARNING
> > + "HPET counter not counting. HPET disabled\n");
> > + goto out_nohpet;
> > + }
> > +
> > /* Initialize and register HPET clocksource
> > *
> > * hpet period is in femto seconds per cycle
> >
> > --
> > -
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> >
> -
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