Messages in this thread | | | Date | Fri, 3 Jun 2022 22:14:30 +0800 | Subject | Re: [PATCH V15 10/24] LoongArch: Add other common headers | From | WANG Xuerui <> |
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On 6/3/22 22:01, Jason A. Donenfeld wrote: > Hi Arnd, > > On Fri, Jun 03, 2022 at 03:55:27PM +0200, Arnd Bergmann wrote: >> On Fri, Jun 3, 2022 at 3:40 PM Jason A. Donenfeld <Jason@zx2c4.com> wrote: >>> On Fri, Jun 03, 2022 at 03:20:39PM +0800, Huacai Chen wrote: >>>> diff --git a/arch/loongarch/include/asm/timex.h b/arch/loongarch/include/asm/timex.h >>> "Currently only used on SMP for scheduling" isn't quite correct. It's >>> also used by random_get_entropy(). And anything else that uses >>> get_cycles() for, e.g., benchmarking, might use it too. >>> >>> You wrote also, "we know that all SMP capable CPUs have cycle counters", >>> so if I gather from this statement that some !SMP CPUs don't have a >>> cycle counter, though some do. If that's a correct supposition, then >>> you may need to rewrite this file to be something like: >> The file is based on the mips version that deals with a variety of >> implementations >> and has the same comment. >> >> I assume the loongarch chips all behave the same way here, and won't need >> a special case for non-SMP. > Oh good. In that case, the code is fine and I suppose the comment could > just be removed.
In addition, the rdtime family of instructions is in fact guaranteed to be available on LoongArch; LoongArch's subsets all contain them, even the 32-bit "Primary" subset intended for university teaching -- they provide the rdtimeh.w and rdtimel.w pair of instructions that access the same 64-bit counter. So I think the comments are probably just leftovers from a very early port; the LoongArch development started way before it was publicized.
And yes, the comment block re get_cycles usage can be removed altogether.
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