Re: [SeaBIOS] [PATCH v2] add acpi pmtimer support

[Kevin O'Connor]

On Tue, Aug 14, 2012 at 07:29:19AM +0200, Gerd Hoffmann wrote:
> This patch makes seabios use the acpi pmtimer instead of tsc for
> timekeeping.  The pmtimer has a fixed frequency and doesn't need
> calibration, thus it doesn't suffer from calibration errors due to a
> loaded host machine.

The patch looks okay to me, but is it still needed?  (I recall seeing
something on the kvm list about a bug fix to the main timer.)

[...]
> +static u64 pmtimer_get(void)
> +{
> u16 ioport = GET_GLOBAL(pmtimer_ioport);
> u32 wraps = GET_LOW(pmtimer_wraps);
> u32 pmtimer = inl(ioport);
> if (pmtimer < GET_LOW(pmtimer_last)) {
>    wraps++;
>    SET_LOW(pmtimer_wraps, wraps);
> }
> SET_LOW(pmtimer_last, pmtimer);
> dprintf(9, "pmtimer: %u:%u\n", wraps, pmtimer);
> return (u64)wraps << 24 | pmtimer;

BTW, why is this "<< 24", and if it should be that way, shouldn't the
pmtimer be "inl(ioport) & 0xffffff" ?

-Kevin