On Fri, Nov 2, 2018 at 3:53 PM Atish Patra <atish.patra@xxxxxxx> wrote: > > On 11/2/18 8:50 AM, Sudeep Holla wrote: > > On Fri, Nov 02, 2018 at 10:11:38AM -0500, Rob Herring wrote: > >> On Fri, Nov 2, 2018 at 8:31 AM Sudeep Holla <sudeep.holla@xxxxxxx> wrote: > >>> > >>> On Fri, Nov 02, 2018 at 08:09:39AM -0500, Rob Herring wrote: > >>>> On Thu, Nov 1, 2018 at 6:04 PM Atish Patra <atish.patra@xxxxxxx> wrote: > >>>>> > >>>>> Define a RISC-V cpu topology. This is based on cpu-map in ARM world. > >>>>> But it doesn't need a separate thread node for defining SMT systems. > >>>>> Multiple cpu phandle properties can be parsed to identify the sibling > >>>>> hardware threads. Moreover, we do not have cluster concept in RISC-V. > >>>>> So package is a better word choice than cluster for RISC-V. > >>>> > >>>> There was a proposal to add package info for ARM recently. Not sure > >>>> what happened to that, but we don't need 2 different ways. > >>>> > >>> > >>> We still need that, I can brush it up and post what Lorenzo had previously > >>> proposed[1]. We want to keep both DT and ACPI CPU topology story aligned. > >> > >> Frankly, I don't care what the ACPI story is. I care whether each cpu > > > > Sorry I meant feature parity with ACPI and didn't refer to the mechanics. > > > >> arch does its own thing in DT or not. If a package prop works for > >> RISC-V folks and that happens to align with ACPI, then okay. Though I > >> tend to prefer a package represented as a node rather than a property > >> as I think that's more consistent. > >> > > > > Sounds good. One of the reason for making it *optional* property is for > > backward compatibility. But we should be able to deal with that even with > > node. > > > > If you are introducing a package node, can we make cluster node > optional? I feel it is a redundant node for use cases where one doesn't > have a different grouped cpus in a package. Certainly not. A common doc can make every level optional and each arch can define what's mandatory. > We may have some architecture that requires cluster, it can be added to > the DT at that time, I believe. > > >> Any comments on the thread aspect (whether it has ever been used)? > >> Though I think thread as a node level is more consistent with each > >> topology level being a node (same with package). > >> > > Not 100% sure, the only multi threaded core in the market I know is > > Cavium TX2 which is ACPI. > > > > Any advantages of keeping thread node if it's not being used. If I am > not wrong, we can always use multiple cpuN phandles to represent SMT > nodes. It will result in less code and DT documentation as well. It's more consistent to make each level a node IMO and we've already discussed and defined it this way. I don't see how it's really less code or documentation. BTW, powerpc defined threads with multiple reg entries in the cpu nodes. You could do that if you wanted. Rob
