On Fri, Feb 26, 2016 at 12:27 PM, Will Deacon <will.deacon@xxxxxxx> wrote: > On Thu, Feb 25, 2016 at 05:26:34PM -0800, David Daney wrote: >> On 02/23/2016 11:36 AM, Rob Herring wrote: >> >On Fri, Feb 19, 2016 at 05:13:17PM -0800, David Daney wrote: >> >>From: Ganapatrao Kulkarni <gkulkarni@xxxxxxxxxxxxxxxxxx> >> >> >> >>ADD device tree node parsing for NUMA topology using device >> >>"numa-node-id" property distance-map. >> > >> >I still want an adequate explanation why NUMA setup cannot be done with >> >an unflattened tree. PowerPC manages to do that and should have a >> >similar init flow being memblock based, so I would expect arm64 can too. >> >> Many things could be done. Really, we want to know what *should* be done. >> >> In the context of the current arm64 memory initialization we (more or less) >> do: >> >> 1) early_init_fdt_scan_reserved_mem(); >> 2) memory_present() >> 3) sparse_init() >> 4) other things >> 5) unflatten_device_tree() >> >> We are already reading information out of the FDT at #1. >> >> This patch set adds a step between 1 and 2 where we read NUMA information >> out of the FDT. >> >> Hypothetically, it might be possible to rewrite the arm64 setup code so that >> the ordering was different, and the NUMA setup was done on the unflattened >> tree, but that would certainly be a much more invasive patch. > > I just looked at what PPC get up to, and there's really not an obvious > way we could do that on arm64. They run whole swathes of the kernel > with the MMU off directly from head.S to parse the flattened tree and > get memblock up really early. On arm64, the head.S environment is > considerably more hostile, and I don't think we'd want to do that (not > to mention the interaction with EFI stub). > > So I'm perfectly happy for this to operate on the flattened tree. Of course you are. The code is not in your tree. I'm all for keeping things out of /arch, but just want to understand what are the dependencies which aren't clearly spelled out here. Rob -- 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
