On Wed, Feb 26, 2014 at 03:48:58PM +0000, Catalin Marinas wrote:
My concern is that the MPIDR is just considered a unique ID. The ARMv8 relaxes the requirement so that it no longer needs to start at 0 and increase monotonically. I checked with the architecture guys here and they still expect the affinity hierarchy to be described by MPIDR but we can have holes in the range for certain levels (i.e. an affinity level may not start at 0 and may not even increase monotonically for subsequent CPUs).
I don't think anything has a problem with holes in the number range, the only thing I can think of which imposes that requirement is the DT binding but obviously that's not relevant if we are using MPIDR. The core topology documentation explicitly says that these are physical IDs and entirely up to the architecture/platform. It'd seem odd given that we have hotplug support.
What problems do you anticipate?
So we can either add a tolerant MPIDR parsing or we simply assume that the topology is _flat_ when DT doesn't provide the information.
Right, that's what the current code does but I'm not sure it's the best option.