Hi, Wolfgang

Wolfgang Grandegger wrote:

Felix Radensky wrote:
  

quoted

Hi,

Almost all MPC85XX based systems have the compatible=:"fsl-i2c" in
respective
i2c device tree nodes. This causes FSL i2c driver to use the following
"backward
compatible" values: FSR=0x31 DFSR=0x10. This is regardless of CCB clock
frequency and i2c clock prescaler.

On my custom MPC8536 based board with 432MHz CCB clock this results in
65KHz i2c clock frequency (checked with scope). U-Boot correctly configures
the clock to 400KHz.

I've fixed the problem by modifying device tree to use different
compatible value,
similar to what socrates board does. Is this the right approach ?
    

Are you aware of the properties described in
"Documentation/powerpc/dts-bindings/fsl/i2c.txt":

http://lxr.linux.no/#linux+v2.6.32/Documentation/powerpc/dts-bindings/fsl/i2c.txt

Wolfgang.

  

Sure, I'm aware of these properties. I've used

compatible = "fsl,mpc8543-i2c", "fsl-i2c";
clock-frequency = <400000>;

for my custom board.

I think, however, that device trees for FSL reference designs should use 
them as well, to avoid setting i2c
clock to some strange values. I may be wrong, but I think most custom 
board developers borrow from
reference device trees, so having a sane starting point would help.

Thanks.

Felix.