Re: [PATCH V15 10/24] LoongArch: Add other common headers

[WANG Xuerui]

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@xxxxxxxxx> 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.