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From: Wolfgang Grandegger <wg@grandegger.com>
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Cc: linuxppc-dev@ozlabs.org, Wolfgang Denk <wd@denx.de>,
	Detlev Zundel <dzu@denx.de>, linux-i2c@vger.kernel.org
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Piotr Ziêcik wrote:
> Monday 18 May 2009 16:29:04 Wolfgang Grandegger napisa³(a):
>>> I have simple question about bus speed setting support. Existing
>>> implementation uses default safe speed if there is no 'clock-frequency'
>>> property in i2c node. Comments in code suggest that this behaviour is
>>> left for backward compatibility only. Should I make the 'clock-frequency'
>>> property mandatory for a new type of I2C controller (MPC5121) ?
>> I don't think so, for the same backward compatibility reason as for the
>> other boards. But the DTS file might be changed to use clock-frequency.
> 
> In my opinion implementing "backward compatilility" for MPC5121 is not good
> idea. MPC5121 I2C support is completly new thing in mainline. Simply, there is 
> no DTS with which I have to be compatible. Adding backward compatibility
> with nothing may be confusing.

There is a port for the  MPC5121 in mainline since 2.6.25 including DTS
file:

http://lxr.linux.no/linux+v2.6.25/arch/powerpc/boot/dts/mpc5121ads.dts

If it was really usable or even used is another question. But it's fine
for me be more restrictive, e.g. print a warning when save values are
selected.

Wolfgang.