Re: powerpc/85xx: Add support for the "socrates" board (MPC8544)

Anton Vorontsov wrote:

On Tue, Mar 31, 2009 at 09:05:28AM -0600, Grant Likely wrote:
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+       soc8544@e0000000 {
+               #address-cells = <1>;
+               #size-cells = <1>;
+               device_type = "soc";

Drop device_type here too.

Grrr, I just realized that removing the devices type "soc" has broken
fsl_get_sys_freq(). See:

http://lxr.linux.no/linux+v2.6.29/arch/powerpc/sysdev/fsl_soc.c#L80

We need a quick fix and we could take the occasion to establish a common
function for the MPC52xx as well, but it's not obvious to me how to find
the SOC node without the device type property.

SoC node should have a compatible property, just like everything else.

compatible = "fsl,mpc8544-immr";  (immr == Internally Memory Mapped Registers)

Many other boards already do this.

Yes, it does, but searching for the SOC node is not straight-forward
because there is no common compatibility string but many CPU-specific
compatibility strings, e.g. "fsl,mpc8560-immr", etc. Have I missed
something?

Choose a new value ("fsl,mpc-immr" perhaps?), document exactly what it
means, and add add it to the end of the compatible list.

As Scott Wood once pointed out, IMMR does not exists for MPC85xx
parts. There it's called CCSR.

See this thread:

http://www.mail-archive.com/linuxppc-dev@ozlabs.org/msg12665.html

I still think that
"fsl,mpc83NN-immr", "fsl,soc", "simple-bus" for 83xx
and
"fsl,mpc85NN-ccsr", "fsl,soc", "simple-bus" for 85xx

would be OK, at least to start with. We can always deprecate "fsl,soc"
compatible in favour of something more elegant, but "fsl,soc" should be
just fine to replace device_type = "soc".

Also, there is another good thing about "fsl,soc" -- U-Boot already
finds it for 83xx CPUs. ;-)

Ugh! I just realize the full impact of removing device type "soc". It
will break compatibility with U-Boot for many boards. Is it worth it?

Wolfgang.