[Skiboot] [RFC PATCH skiboot] npu2: Add nvlink2 interconnect information

[Reza Arbab]

On Wed, Aug 15, 2018 at 06:26:24PM +1000, Alexey Kardashevskiy wrote:
>GPUs on Redbud and Sequoia platforms are interconnected between each
>other in groups of 2 or 3 GPUs. The problem with that is if we decide
>to pass one of GPUs in a group to the userspace (and potentially a guest),
>we need to make sure that interconnectd link does not get enabled.
>
>The GPU firmware provides a way to disable links on a GPU. However we
>want to disable only links to other GPUs which are not in the same guest
>so we need a map of what nvlink is connected to what.
>
>This adds an "ibm,nvlinks" property to every GPU in a "GPUn" slot
>with phandles to peer GPUs and NPU PHB, the index in the property is GPU's
>link number.

Seems to work just fine on the Redbud I tried.

You'll probably get asked to add this new property to 
doc/device-tree/nvlink.rst.

-- 
Reza Arbab