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SubjectRe: [patch 7/7] x86: hpet: Cleanup the clockevents init and register code

* Thomas Gleixner <tglx@linutronix.de> wrote:

> @@ -884,6 +835,14 @@ int __init hpet_enable(void)
> goto out_nohpet;
>
> /*
> + * The period is a femto seconds value. Convert it to a
> + * frequency.
> + */
> + freq = FSEC_PER_SEC;
> + do_div(freq, hpet_period);
> + hpet_freq = freq;

Something i just noticed: with a typical hpet frequency of around 14 MHz we get
a period of 71428571 femtoseconds.

Our HPET_MAX_PERIOD is 100000000 at the moment, so our limits look like this:

100000
71428571
100000000

Note how close the max period (lowest frequency) is to our typical value!

So if there's a 10 MHz hpet somewhere, with just slightly below spec, we'd fail
due to:

if (hpet_period < HPET_MIN_PERIOD || hpet_period > HPET_MAX_PERIOD)
goto out_nohpet;

unless i got my numbers wrong it might be worth upping the max period to
1000000000, to allow down to 1 MHz hpet frequencies. Or at least up it enough
to make 10 MHz possible modulo small noise.

Patch looks good:

Reviewed-by: Ingo Molnar <mingo@elte.hu>

Thanks,

Ingo


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