i2c clock running at 16Khz

Jean Delvare khali at linux-fr.org
Tue Jan 25 20:59:14 CET 2005


Hi Oliver,

> > BTW, may I ask how you did measure the frequency?
> 
> I hooked an oscilloscope to the clock and data pins.

Impressive :) I wish I had the necessary hardware to do so.

> > May I know the SMBus speed (or rather slowness) is so important to
> > you?
> 
> The 3rd party board I am trying to use does not seem to like the
> slower  clock rate.

Strange, usually most chips are fine with that (which is why they chose
it, I guess).

OK, you may try to apply the attached patch to your kernel tree. It
attempts to change a PCI configuration bit which *might* switch the
SMBus speed from 16kHz to 64kHz. I am not able to verify whether it
works or not since I do not have an oscilloscope, and the i2c-viapro is
poll-based so measuring performance from userspace doesn't help (the
poll delay dominates the SMBus speed by a huge factor). Also it might
not work for all VIA chips, I have no datasheets, I can't say. You tell
me if it works for you :)

-- 
Jean Delvare
http://khali.linux-fr.org/
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