Re: Freescale MPC5554 device tree (was: cross-compiling Linux for PowerPC e200 core?)

[Grant Likely <grant.likely@secretlab.ca>]

On Fri, Mar 12, 2010 at 3:36 PM, David Gibson
<david@gibson.dropbear.id.au> wrote:
> On Fri, Mar 12, 2010 at 05:14:56AM -0700, Grant Likely wrote:
>> 2010/3/11 N=E9meth M=E1rton <nm127@freemail.hu>:
> [snip]
>> > +
>> > + =A0 =A0 =A0 cpus {
>> > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 #address-cells =3D <1>;
>> > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 #size-cells =3D <0>;
>> > +
>> > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 cpu@0 {
>> > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 device_type =3D "cpu";
>> > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 compatible =3D "PowerPC,=
5554";
>>
>> I'd rather see the same convention used here as for all the other
>> compatible values in this file. =A0ie:
>>
>> compatible =3D "fsl,mpc5554-e200z6", "fsl,powerpc-e200z6";
>>
>> Dave, what do you think?
>
> Well, you could add those too, but "PowerPC,5554" should probably
> remain.
>
> The historical background here is that in the original OF spec, driver
> matching was done on node name, and only then on compatible.
> Essentially the node name was treated as an implicit first entry in
> the compatible list. =A0The the generic names convention came along, and
> instead name became a human readable generic type for the device
> ("ethernet", "i2c", etc..).
>
> That convention has been widely used since long before flat trees
> existed, but for some reason it was never really used for cpu nodes;
> they remained as "PowerPC,XXXX" or whatever. =A0Because the varying
> names of cpu nodes was sometimes awkward to deal with in bootloaders,
> we decided it would be sensible to apply the generic names convention
> here too, so "cpu@X". =A0But then, the previous node name, which was
> treated as being prepended to compatible, should now explicitly be put
> into compatible.

In this particular case, we're talking about a part that has never
previously been described in a device tree.  So, since this is
something entirely new, what is the value in preserving the
PowerPC,XXXX style when there isn't any code that will be relying on
it?

g.

--=20
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.