Booting Imac G5
l_indien at magic.fr
Thu Nov 18 09:26:00 EST 2004
On Wed, 2004-11-17 at 22:30, Benjamin Herrenschmidt wrote:
> On Wed, 2004-11-17 at 15:56 +0100, J. Mayer wrote:
> > On Mon, 2004-11-15 at 13:48, Segher Boessenkool wrote:
> > > >>> RTC is probably in the SMU...
> > > >>
> > > >> It is.
> > > >
> > > > Apple say it's an external RTC in the developper notes. The problem is
> > > > to get an I2C driver for the SMU. With the forth code, seems that it
> > > > can
> > > > be made ;-)
> > >
> > > As far as I know you just ask the SMU the time, you don't have to
> > > talk to the IIC yourself. Or maybe that has changed... checking...
> > > no, it hasn't (the actual commands did change, though).
> > OK, I made a confusion between the SMU system clock, which is accessed
> > via I2C and the RTC which is directly accessed.
> > I still need to test my code, then I will have (soon) a RTC driver...
> Which i2c bus is it on ? You may need to use the low-level i2c routines
> in pmac_low_i2c instead of the high level driver to access the RTC early
> at boot.
There seem to be an I2C controller (or pseudo I2C, as I saw in Apple
code) in the SMU with two I2C buses. One bus has two devices connected,
according to the OF tree: the system clock (used to control the CPU
clock, as I understand it) and the temperature sensor located on the
As the RTC is accessed directly using SMU commands, I2C won't be needed
early at boot time.
J. Mayer <l_indien at magic.fr>
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