From: Jesse Barnes <jbarnes@engr.sgi.com>
To: Vojtech Pavlik <vojtech@suse.cz>
Subject: Re: device driver for the SGI system clock, mmtimer
Date: Thu, 16 Sep 2004 11:35:52 -0700
User-Agent: KMail/1.7
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
References: <200409161003.39258.bjorn.helgaas@hp.com> <200409160909.12840.jbarnes@engr.sgi.com> <20040916181426.GA5052@ucw.cz>
In-Reply-To: <20040916181426.GA5052@ucw.cz>
MIME-Version: 1.0
Content-Type: text/plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
Message-Id: <200409161135.52987.jbarnes@engr.sgi.com>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1425
Lines: 32

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
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/