On Thu, Aug 22, 2013 at 05:28:10PM +0100, Sudeep KarkadaNagesha wrote:
> On 22/08/13 16:50, Mark Rutland wrote:
> > On Thu, Aug 22, 2013 at 04:32:10PM +0100, Sudeep KarkadaNagesha wrote:
> >> On 22/08/13 12:59, Mark Rutland wrote:
> >>> On Wed, Aug 21, 2013 at 11:48:12PM +0100, Stephen Warren wrote:
> [...]
> >>>>
> >>>> I'd suggest/bike-shed that operating-points-device is not the correct
> >>>> property name; it somehow implies that the other device actively defines
> >>>> the OPPs for this device, rather than just happening to have the same
> >>>> OPPs. Perhaps "operating-points-identical-to"?
> >>>>
> >>>
> >>> I'd rather not have properties that point elsewhere and say "treat me
> >>> the same as this node". I'd rather we have common properties as
> >>> described above.
> >>>
> >> Agreed, but for platforms with multiple CPU clusters, since we have only
> >> one /cpus node, we ned to have table node which is arguable if node has
> >> represent a device(as mentioned above)
> >
> > I agree that this seems wasteful of space, but I really don't think that
> > pointing at another device you want the OPPs of is the best way of
> > describing the linkage, and I suspect we'll get all sorts of stupid bugs
> > resulting from that style of binding.
> >
> > Consider the following (properties trimmed for brevity):
> >
> > cpus {
> > cpu0: cpu@0 {
> > operating-points-identical-to = <&cpu1>;
> > };
> > cpu1: cpu@1 {
> > operating-points = <0 100>,
> > <23 47>,
> > <62 970>;
> > }
> > };
> >
> > If we boot a UP kernel on the above, I assume we won't read the info for
> > cpu1, and thus we won't get operating points info for cpu0. Worse, what
> > if cpu1 has status="disabled"? Does that make its OPP table invalid?
> > What if the bootloader drops cpu1?
> >
> Another question :), does status property dictate the validity of the
> other properties in the node(not specific to above example, in general)?
That depends on what the binding in question describes for a disabled
status. In general, if a node is disabled I would imagine that
attempting to derive any knowledge from it is not a good idea.
>
> But I agree that this indirect linkage is broken as boot-loaders can
> drop the cpu node holding OPP.
>
> IMO fallback method would be reasonable(and much cleaner compared to a
> separate node) if it can even accommodate multiple cpu clusters.
Well, it may be that for separate clusters we just have to describe the
information per-cpu...
>
> > I really don't like indirecting linkage to a property through an
> > arbitrary node, simply because it happened to have the same property. It
> > creates an artificial depdendency that will lead to problems.
> >
> I totally agree on this.
Cool.
Thanks,
Mark.
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