[PATCH] i2c-cpm: Add flexibility for I2C clock frequency and filter.

Mike Ditto mditto at consentry.com
Thu Nov 6 11:35:03 EST 2008


David Gibson wrote:
> What does worry me, however, is the description says it's about
> whether the driver "should" enable the filter.  Generally the device
> tree doesn't attempt to say what users "should" do with the hardware,
> just what the characteristics of the hardware are.
>
> What's the underlying difference here that affects the driver's choice
> to enable the filter or not?

I think it's a hardware/environment design parameter - e.g. if the I2C
bus has hot-pluggable devices, long PCB traces, or a hierarchy of
multiplexed bus segments, these can result in a noisy SCL signal that
needs to be filtered.  It's also a recommended mitigation for errata
in certain CPU revs.

					-=] Mike [=-



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