Wink Saville wrote:
Arjan van de Ven wrote:
Actually, we need to ask the CPU/System makers to provide a system wide
timer that is independent of the given CPU. I would expect it quite
simple
they exist. They're called pmtimer and hpet.
pmtimer is port io. hpet is memory mapped io.
Thanks for the info. I took a look at Documentation/hpet.txt and
drivers/char/hpet.c
and see that hpet_mmap is implemented in the driver but nothing hpet.txt
indicates
what is being mapped.
Could you point me to any other documentation? I did find the following:
http://www.intel.com/hardwaredesign/hpetspec_1.pdf
Are you aware of any example user code that uses the mmap capability of
hpet?
Generally user mode code should just be using gettimeofday. When the TSC
is usable as a sane time source, the kernel will use it. When it's not,
it will use something else like the HPET, ACPI PM Timer or (at last
resort) the PIT, in increasing degrees of slowness.
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