Re: [Xen-devel] [PATCH] xen/arm: copy cpu clock-frequency to CPU DT node.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2013-11-04 at 13:35 -0500, Jon Fraser wrote:
> On Mon, 2013-11-04 at 17:12 +0000, Ian Campbell wrote:
> > On Fri, 2013-11-01 at 16:58 -0400, Jon Fraser wrote:
> > > When creating the CPU DT node, copy the clock-frequency if present.
> > > 
> ...
> > Julien's the expert but I think you need to use dt_property_read_u32
> > here, to get the correct endianness conversion (as well as for pure
> > forms sake of using the correct API for the job).
> > 
> I'll fix that.
> 
> > >              break;
> > >          }
> > >      }
> > > @@ -457,6 +459,12 @@ static int make_cpus_node(const struct domain *d, 
> > > void *fdt,
> > >          if ( res )
> > >              return res;
> > >  
> > > +        if (clock_frequency) {
> > > +            res = fdt_property_cell(fdt, "clock-frequency", *(u32 
> > > *)clock_frequency);
> > 
> > I suppose there ought to be some API for this side of things too, but I
> > can't see it right now...
> > 
> > Note that fdt_property_cell contains a cpu_to_fdt32 so it is converting
> > while the read of the property not, so I think the code is broken as is?
> 
> Yesss, it is broken.  When I checked the property in /proc/device-tree,
> I failed to realize it was endian swapped.

I guess nothing much critical is relying on this value. What is it
supposed to be used for?
linux/Documentation/devicetree/booting-without-of.txt seems to imply it
is mostly optional for non-PPC.

Ian.


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