Anyway, you are doing some great job here and I'ld be (somehow) available
for validation of the fixes you might come with, if you get some time .
Thank you
Frank
> -----Original Message-----
> From: george anzinger [mailto:george@mvista.com]
> Sent: 5 février, 2003 15:39
> To: Isabelle, Francois
> Cc: high-res-timers-discourse@lists.sourceforge.net;
> linux-kernel@vger.kernel.org
> Subject: Re: High-Res-Timers: Unexpected "lock" during "Calibrating
> delay loop "
>
>
> Isabelle, Francois wrote:
> > Just wanted to add this: this seems to be reproducible on all 486
> >
>
> I hope to get a chance to look at this today. Thus far, I know that
> the PIT version does not keep good time in the face of timers of
> resolution > 1/HZ, i.e. the "_HR" clocks.
>
> This has to do with the fact that we have only one interrupt source
> and must change it to get the sub jiffies interrupts. In the process
> we loose track of where the jiffies interrupt should be. There is an
> attempt to use the second PIT timer to cover for this, but
> assumptions
> are made here that may not be right. (This timer is used for memory
> refresh and is set up by the BIOS. We can not change it and
> we assume
> that it has a given period. I suppose we could attempt to
> measure the
> period, but thus far we have assumed that these sorts of machines
> would not require high res timers and have not tried to run
> down these
> issues.
>
> A side issue is that the timers seem to not follow the spec (at least
> on my test machine) in the regard that a status bit is supposed to
> indicate when the latch has been loaded after a program has been
> output. I can easily find cases where a wait for the bit to
> change is
> followed by a read of the latch which returns a stale value. I
> suppose some of this has to do with a large difference
> between the cpu
> clock and the timer clock.
> >
> >>-----Original Message-----
> >>From: Isabelle, Francois [mailto:Francois.Isabelle@ca.kontron.com]
> >>Sent: 4 février, 2003 09:04
> >>To: high-res-timers-discourse@lists.sourceforge.net;
> >>'george@mvista.com'
> >>Cc: linux-kernel@vger.kernel.org
> >>Subject: High-Res-Timers: Unexpected "lock" during
> "Calibrating delay
> >>loop "
> >>
> >>
> >>Hi,
> >> we are having an unexpected problem with the HR patch(
> >>regardless of
> >>the patch you sent which compiled just fine ). The board uses
> >>a 486DX cpu,
> >>so there is no support for TSC nor ACPI, the only thing we
> >>have is the PIT.
> >>
> >>Without highres, the kernel boots properly, with highres
> >>enabled, the kernel
> >>passes "time_init()" put it hangs in "calibrate_loop() , ( I
> >>though it hung
> >>for real, but it get passed the loop after a while) "
> >>
> >>Seems like the tick is VERY SLOW..
> >>
> >>The PIT has been tested on this board, and without HR, the
> >>kernel boots fine
> >>... if you have any hints, they would be welcome.
> >>
> >>The keyboard detection routine timeouts so the system is
> >>quiet unuseable and
> >>I can't get the calibration results yet.
> >>
> >>
> >>Frank
> >>
> >>
> >>
> >>
> >>
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>
>
>
-- George Anzinger george@mvista.com High-res-timers: http://sourceforge.net/projects/high-res-timers/ Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml
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