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    SubjectRe: device driver for the SGI system clock, mmtimer
    Date
    On Thursday, September 16, 2004 11:14 am, Vojtech Pavlik wrote:
    > On Thu, Sep 16, 2004 at 09:09:12AM -0700, Jesse Barnes wrote:
    > > On Thursday, September 16, 2004 9:03 am, Bjorn Helgaas wrote:
    > > > Christoph Lameter wrote:
    > > > > The timer hardware was designed around the multimedia timer
    > > > > specification by Intel but to my knowledge only SGI has implemented
    > > > > that standard. The driver was written by Jesse Barnes.
    > > >
    > > > As far as I can see, drivers/char/hpet.c talks to the same hardware.
    > > > HP sx1000 machines (and probably others) also implement the HPET.
    > >
    > > No, it's different hardware.
    >
    > mmtimer and hpet are the same hardware actually, just a different
    > specification revision, hpet being the newer one.

    Well, the SHub RTC hardware (which mmtimer accesses) isn't really HPET or
    mmtimer hardware, but I tried to make the mmtimer *API* useful for HPET style
    hardware. The idea was to have several drivers supporting the mmtimer API
    with different hardware underneath.

    > HPET registers are MMIO so it's in theory possible, while not really
    > useful if you're using it as your system timer as well.

    I don't think anyone does this.

    Jesse
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