On 17/09/2022 19:47, Marc Zyngier wrote: > On Sat, 17 Sep 2022 17:51:20 +0100, > Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> wrote: >> >> On 16/09/2022 14:30, Jean-Philippe Brucker wrote: >>> QEMU uses both "arm,armv8-timer" and "arm,armv7-timer" as compatible >>> string. Although it is unlikely that any guest relies on this, we can't >>> be certain of that. Therefore, add these to the schema. Clean up the >>> compatible list a little while at it. >>> >>> Signed-off-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx> >> >> I guess you wanted to say QEMU uses "arm,armv8-timer" followed by >> "arm,armv7-timer", because otherwise I would understand it that either >> that or that. Anyway, is it a valid (virtualized) hardware? Is ARMv8 >> timer really, really compatible with ARMv7 one? > > Yes. There isn't a shred of difference between the two in the earlier > revisions of the ARMv8 architecture, and none of the differences > introduced in later revisions are exposed to DT anyway. > >> I don't think we should document invalid setups out-of-tree, just >> because they are there, and something like this was also expressed by Rob: >> https://lore.kernel.org/all/20220518163255.GE3302100-robh@xxxxxxxxxx/ > > This is, on the contrary, something that is perfectly valid. For > example, a system running a 32bit OS on a 64bit system is perfectly > entitled to expose both (v8 because that's what the HW is, v7 because > that's what the OS is the most likely to understand). > > You may find it odd, but that: > > - expresses something that is actually required > > - is what I, as the original author of this binding, have always > considered valid > > - has been valid for a long time (10+ years) before you decided it > suddenly wasn't > > I understand that the "DT police" has high standards, but this has > been around for much longer, and it isn't because the conversion to > schema is imperfect that you can rewrite history. > > As for the patch, I'd remove the QEMU reference and the deprecation. > This format is perfectly allowed, and is in use in most VMMs out > there. Yes, DT is an ABI. Thanks for the explanation, actually enough was to say that it is perfectly valid combination describing hardware. :) Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> Best regards, Krzysztof
