On Mon, Jan 28, 2013 at 09:02:40AM +0000, Mark Rutland wrote:
> On Fri, Jan 25, 2013 at 07:15:48PM +0000, Kukjin Kim wrote:
> > Tomasz Figa wrote:
> >
> > [...]
> >
> > > > Well, the number of CPU types does not grow rapidly. It will be much
> > > > less than one per SoC -- so keeping the list up to date shouldn't be
> > > > that much effort.
> > > >
> > > > For ARM1176JZF-S, it could make sense for the comatible list to be
> > > >
> > > > "arm,arm1176jzf-s", "arm,arm1176"
> > > >
> > > > ...since the differences between 1176 variants are software probeable
> > > > (i.e., whether there is an FPU or not). AFAIK the J, Z apply to all
> > > > ARM1176, and the -S (synthesisable RTL) is nothing to do with software.
> > > > The kernel probably only really needs to know "arm,arm1176".
> > >
> > > OK. So the conclusion is that I should change the cpus node to following:
> > >
> > > cpus {
> > > cpu {
> >
> > cpu@0 { ?
>
> As the CPU has no MPIDR, and thus doesn't have a reg property, there's no reason
> to have a unit address. Just "cpu" should be fine.
>
> >
> > > compatible = "arm,arm1176jzf-s", "arm,arm1176";
> > > };
> > > };
> > >
> > > Am I right?
> > >
> > I think so :-)
> >
> > - Kukjin
> >
>
> As Dave pointed out, the "jzf-s" portion might be superfluous. It's worth
> having the "arm,arm1176", though.
I think we should always have a fully-qualified part name as the first
compatible entry, following general devicetree policy. It's better to
have this and not need it than to discover later that we want it and
incompatibly backport it in.
Before deciding, do we follow a consistent policy for other CPUs, such
as arm1136?
The issues there are similar: the only software-visible difference between
arm1136j-s and arm1136jf-s should be the absence/presence of VFP, and it
looks like the code in vfpmodule.c should be able to probe it.
Cheers
---Dave
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