On Tue, Feb 25, 2014 at 08:48:38PM +0000, Kumar Gala wrote: > > On Feb 25, 2014, at 5:16 AM, Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> wrote: > > > Hi Stephen, > > > > On Wed, Feb 19, 2014 at 12:20:43AM +0000, Stephen Boyd wrote: > >> (Sorry, this discussion stalled due to merge window + life events) > > > > Sorry for the delay in replying on my side too. > > > >> On 01/17, Lorenzo Pieralisi wrote: > >>> On Thu, Jan 16, 2014 at 07:26:17PM +0000, Stephen Boyd wrote: > >>>> On 01/16, Lorenzo Pieralisi wrote: > >>>>> On Thu, Jan 16, 2014 at 06:05:05PM +0000, Stephen Boyd wrote: > >>>>>> On 01/16, Lorenzo Pieralisi wrote: > >>>>>>> Do we really want to do that ? I am not sure. A cpus node is supposed to > >>>>>>> be a container node, we should not define this binding just because we > >>>>>>> know the kernel creates a platform device for it then. > >>>>>> > >>>>>> This is just copying more of the ePAPR spec into this document. > >>>>>> It just so happens that having a compatible field here allows a > >>>>>> platform device to be created. I don't see why that's a problem. > >>>>> > >>>>> I do not see why you cannot define a node like pmu or arch-timer and stick > >>>>> a compatible property in there. cpus node does not represent a device, and > >>>>> must not be created as a platform device, that's my opinion. > >>>>> > >>>> > >>>> I had what you're suggesting before in the original revision of > >>>> this patch. Please take a look at the original patch series[1]. I > >>>> suppose it could be tweaked slightly to still have a cache node > >>>> for the L2 interrupt and the next-level-cache pointer from the > >>>> CPUs. > >>> > >>> Ok, sorry, we are running around in circles here, basically you moved > >>> the node to cpus according to reviews. I still think that treating cpus > >>> as a device is not a great idea, even though I am in the same > >>> position with C-states and probably will add C-state tables in the cpus > >>> node. > >>> > >>> http://comments.gmane.org/gmane.linux.power-management.general/41012 > >>> > >>> I just would like to see under cpus nodes and properties that apply to > >>> all ARM systems, and avoid defining properties (eg interrupts) that > >>> have different meanings for different ARM cores. > >>> > >>> The question related to why the kernel should create a platform device > >>> out of cpus is still open. I really do not want to block your series > >>> for these simple issues but we have to make a decision and stick to that, > >>> I am fine either way if we have a plan. > >>> > >> > >> Do you just want a backup plan in case we don't make a platform > >> device out of the cpus node? I believe we can always add code > >> somewhere to create a platform device at runtime if we detect the > >> cpus node has a compatible string equal to "qcom,krait". We could > >> probably change this driver's module_init() to scan the DT for > >> such a compatible string and create the platform device right > >> there. If we get more than one interrupt in the cpus node we can > >> add interrupt-names and then have software look for interrupts by > >> name instead of number. > > > > As I mentioned, I do not like the idea of adding compatible properties > > just to force the kernel to create platform devices out of device tree > > nodes. On top of that I would avoid adding a compatible property > > to the cpus node (after all properties like enable-method are common for all > > cpus but still duplicated), my only concern being backward compatibility > > here (ie if we do that for interrupts, we should do that also for other > > common cpu nodes properties, otherwise we have different rules for > > different properties). > > > > I think you can then add interrupts to cpu nodes ("qcom,krait" specific), > > and as you mentioned create a platform device for that. > > > > Thanks, > > Lorenzo > > So I agree with the statement about adding compatibles just to create platform devices is wrong. However its seems perfectly reasonable for a cpu node to have a compatible property. I don't see why a CPU is any different from any other device described in a DT. I was referring to the /cpus node, not to individual cpu nodes, where the compatible property is already present now. Lorenzo -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
