Date: Thu, 16 Sep 2004 20:14:26 +0200
From: Vojtech Pavlik <vojtech@suse.cz>
To: Jesse Barnes <jbarnes@engr.sgi.com>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>, Christoph Lameter <clameter@sgi.com>,
       linux-kernel@vger.kernel.org, Bob Picco <Robert.Picco@hp.com>,
       venkatesh.pallipadi@intel.com
Subject: Re: device driver for the SGI system clock, mmtimer
Message-ID: <20040916181426.GA5052@ucw.cz>
References: <200409161003.39258.bjorn.helgaas@hp.com> <200409160909.12840.jbarnes@engr.sgi.com>
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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.

> > I think you should look at adding your functionality to hpet.c
> > rather than adding a new driver.
> 
> I think Christoph already looked at that.  And HPET doesn't provide mmap 
> functionality, does it?  I.e. allow a userspace program to dereference the 
> counter register directly?

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.

-- 
Vojtech Pavlik
SuSE Labs, SuSE CR
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