Subject: Re: i2c-powermac fails

From: Jean Delvare <[email-masked]>
Date: Thu, 15 Oct 2009 16:05:13 +0200

On Thu, 15 Oct 2009 22:19:19 +1100, Benjamin Herrenschmidt wrote:
> On Thu, 2009-10-15 at 12:49 +0200, Jean Delvare wrote:
> > Oh. Well, if that was the case, we would see errors all the time, not
> > just during initialization, right? Or does the I2C clock frequency
> > change over time somehow?
> 
> No but maybe we are a bit on the "limit" of the device and some
> registers take long to respond than others ?

Unlikely. The ADT7460 can run at I2C clock rates up to 400 kHz while
the Keywest I2C runs at 25, 50 or 100 kHz if I read the code properly.
I don't know what exact speed is used on Tim's system, apparently it is
read from the hardware in the device tree directly?

We could have low_i2c.c log the I2C clock frequency and/or try to force
the lowest speed (25 kHz) and see if it helps, but I very much doubt
it. And I'd rather wait for Tim to report the result with my last patch
first.

-- 
Jean Delvare