Re: [patch 7/7] x86: hpet: Cleanup the clockevents init and registercode
From: Ingo Molnar
Date: Thu May 19 2011 - 05:33:29 EST
* Thomas Gleixner <tglx@xxxxxxxxxxxxx> 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:
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
if (hpet_period < HPET_MIN_PERIOD || hpet_period > HPET_MAX_PERIOD)
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@xxxxxxx>
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