On Mon, Aug 19, 2013 at 02:56:10PM +0100, Sudeep KarkadaNagesha wrote: > On 19/08/13 14:02, Rob Herring wrote: > > On 08/19/2013 05:19 AM, Mark Rutland wrote: > >> On Sat, Aug 17, 2013 at 11:09:36PM +0100, Benjamin Herrenschmidt wrote: > >>> On Sat, 2013-08-17 at 12:50 +0200, Tomasz Figa wrote: > >>>> I wonder how would this handle uniprocessor ARM (pre-v7) cores, for > >>>> which > >>>> the updated bindings[1] define #address-cells = <0> and so no reg > >>>> property. > >>>> > >>>> [1] - http://thread.gmane.org/gmane.linux.ports.arm.kernel/260795 > >>> > >>> Why did you do that in the binding ? That sounds like looking to create > >>> problems ... > >>> > >>> Traditionally, UP setups just used "0" as the "reg" property on other > >>> architectures, why do differently ? > >> > >> The decision was taken because we defined our reg property to refer to > >> the MPIDR register's Aff{2,1,0} bitfields, and on UP cores before v7 > >> there's no MPIDR register at all. Given there can only be a single CPU > >> in that case, describing a register that wasn't present didn't seem > >> necessary or helpful. > > > > What exactly reg represents is up to the binding definition, but it > > still should be present IMO. I don't see any issue with it being > > different for pre-v7. > > > Yes it's better to have 'reg' with value 0 than not having it. > Otherwise this generic of_get_cpu_node implementation would need some > _hack_ to handle that case. I'm not sure that having some code to handle a difference in standard between two architectures is a hack. If anything, I'd argue encoding a reg of 0 that corresponds to a nonexistent MPIDR value (given that's what the reg property is defined to map to on ARM) is more of a hack ;) I'm not averse to having a reg value of 0 for this case, but given that there are existing devicetrees without it, requiring a reg property will break compatibility with them. Mark. -- 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
