From: "Maciej W. Rozycki" <macro@linux-mips.org>
To: Huacai Chen <chenhc@lemote.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
"open list:MIPS" <linux-mips@vger.kernel.org>,
Fuxin Zhang <zhangfx@lemote.com>,
Zhangjin Wu <wuzhangjin@gmail.com>,
Jiaxun Yang <jiaxun.yang@flygoat.com>
Subject: Re: [PATCH 1/2] MIPS: Loongson-3: Enable COP2 usage in kernel
Date: Fri, 1 May 2020 01:44:32 +0100 (BST) [thread overview]
Message-ID: <alpine.LFD.2.21.2005010117200.851719@eddie.linux-mips.org> (raw)
In-Reply-To: <CAAhV-H6KWnzwB-p6aOL+L_ZXiYsMyzN1MbXeeeTYpimg7jG73w@mail.gmail.com>
On Thu, 30 Apr 2020, Huacai Chen wrote:
> > > diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h
> > > index ce40fbf..0f71540 100644
> > > --- a/arch/mips/include/asm/mipsregs.h
> > > +++ b/arch/mips/include/asm/mipsregs.h
> > > @@ -386,6 +386,7 @@
> > > #define ST0_CU1 0x20000000
> > > #define ST0_CU2 0x40000000
> > > #define ST0_CU3 0x80000000
> > > +#define ST0_MM 0x40000000 /* Loongson-3 naming */
> >
> > please use ST0_CU2, so everybody understands it's COO2
> I see that there is already an alias ST0_XX for ST0_CU3, and I think
> use a ST0_MM for ST0_CU2 is more meaningful in some places (at least
> in traps.c where ST0_XX is also used). If there are places only used
> to describe the CU Mask (such as in stackframe.h), I will use ST0_CU2.
Well ST0_XX is not an alias, because the bit has a different meaning that
has nothing to do with CP3. It just happens to share the bit position in
CP0.Status with ST0_CU3. Yes, ST0_XX is misplaced and misnamed as it
applies to R10k processors only, but it is our legacy from the old days of
chaos and some three processor types supported. This is similar to say
ST0_ERL vs ST0_IEP, which also share the bit position in CP0.Status, but
have different meanings each.
All this could have been cleaned up (e.g. s/ST0_XX/R10K_ST0_XX/) if
someone had the incentive; I occasionally had and poked at these macros,
but apparently missed this one and a couple of other ones. Maybe on some
rainy autumn evening...
However ST0_MM does enable CP2, even if a specific implementation, making
it no different from ST0_CU2 really.
Maciej
next prev parent reply other threads:[~2020-05-13 22:42 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-29 9:38 [PATCH 1/2] MIPS: Loongson-3: Enable COP2 usage in kernel Huacai Chen
2020-04-29 9:38 ` [PATCH 2/2] MIPS: Loongson-3: Calculate ra properly when unwinding the stack Huacai Chen
2020-04-29 18:33 ` [PATCH 1/2] MIPS: Loongson-3: Enable COP2 usage in kernel Thomas Bogendoerfer
2020-04-30 7:54 ` Huacai Chen
2020-05-01 0:44 ` Maciej W. Rozycki [this message]
2020-05-14 5:44 ` Huacai Chen
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