Re: radeon: RFC speed cap detection on ppc64

From: Adam Jackson
Date: Mon Oct 22 2012 - 11:26:02 EST

On 10/19/12 1:43 PM, Lucas Kannebley Tavares wrote:
The radeon driver does speed cap detection on the root PCI device for
the maximum speed with which the adapter can communicate. On ppc64
systems, however, the root device belongs to the Hypervisor, so the
current code would case a null pointer dereference.

I propose to look for the outmost bus with a parent node and get speed
caps from it, though I suppose the cleaner way would be to inspect all
devices along the way and choose the smallest speed cap.

That (walking all parent nodes) is probably the safest thing to do. I'm not sure whether it's optimal. It would likely depend on whether you can meaningfully have a bridge that's faster on the downstream side than on the upstream.

- ajax
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