[i2c] [PATCH] powerpc: i2c-mpc: make speed registers configurable via FDT

Jon Smirl jonsmirl at gmail.com
Fri Aug 1 04:35:50 CEST 2008


On 7/31/08, Grant Likely <grant.likely at secretlab.ca> wrote:
> Your mixing up device tree layout with implementation details.  Device
>  tree layout must come first.  mpc52xx_find_ipb_freq() is just a
>  convenience function that walks up the device tree looking for a
>  bus-frequency property.
>
>  So, instead of making arguments based on available helper functions,
>  make your arguments based on how data should be laid out in the device
>  tree.  Currently mpc5200 bindings simply depend on finding a
>  bus-frequency property in the parent node for determining the input
>  clock and I don't see any pressing reason to change that (though it
>  probably needs to be documented better).
>
>  However, for the complex cases that Trent and Timur are talking about,
>  it makes perfect sense to have an optional property in the i2c node
>  itself that defines a different clock.  Once that decision has been made
>  and documented, then the driver can be modified and the appropriate
>  helper functions added to adapt the device tree data into something
>  useful.

I've having trouble with whether these clocks are a system resource or
something that belongs to i2c. If they are a system resource then we
should make nodes in the root and use a phandle in the i2c node to
link to them.

The phandle in the mpc5200 case could be implicit since it is fixed in silicon.

Is this register in a system register bank or an i2c one?
gur->pordevsr2 & MPC85xx_PORDEVSR2_SEC_CFG

>
>  Remember (and chant this to yourself).  The device tree describes
>  *hardware*.  It does not describe Linux internal implementation details.
>
>
>  g.
>
>


-- 
Jon Smirl
jonsmirl at gmail.com



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