Subject: Re: i2c-mpc clocking scheme

From: Scott Wood <[email-masked]>
Date: Mon, 01 Dec 2008 17:07:16 -0600

Trent Piepho wrote:
> The Linux code could use current-speed to know if it should program the
> registers.  I.e., if current-speed is present and non-zero, then leave the
> frequency registers alone.  Otherwise u-boot or whatever might not have
> programmed the I2C controller and the driver can do what it's doing now.

I suppose.  I was thinking that Linux could just check to see whether 
the current divider value appears to be valid, but it seems that all 
values including zero can be valid. :-(

>> When does the guest really care what the specific i2c bus frequency is, if 
>> it's not going to change it?
> 
> I don't know of a real reason.  Maybe an I2C device where the clock speed
> makes a difference?  Maximum polling rate or something?  Is there reason
> the CPU clock and the CCB frequency need to be in the device tree?

I'm fine with including it for informational purposes, it just doesn't 
seem quite as necessary.

-Scott