From: Segher Boessenkool <segher@kernel.crashing.org>
To: "Pali Rohár" <pali@kernel.org>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
Nicholas Piggin <npiggin@gmail.com>
Subject: Re: [PATCH v1] powerpc/64: Set default CPU in Kconfig
Date: Fri, 16 Dec 2022 13:15:43 -0600 [thread overview]
Message-ID: <20221216191543.GE25951@gate.crashing.org> (raw)
In-Reply-To: <20221215204202.mbw2ij4ou7t2ttpv@pali>
Hi!
On Thu, Dec 15, 2022 at 09:42:02PM +0100, Pali Rohár wrote:
> On Wednesday 07 December 2022 14:38:40 Christophe Leroy wrote:
> > default "power8" if POWER8_CPU
> > default "power9" if POWER9_CPU
> > default "power10" if POWER10_CPU
> > + default "e500mc64" if E5500_CPU
>
> Now I'm looking at this change again... and should not E5500_CPU rather
> enforce -mcpu=e5500 flag? I know that your patch moves e500mc64 flag
> from the Makefile to Kconfig, but maybe it could be changed in some
> other followup patch...
>
> Anyway, do you know what is e500mc64 core? I was trying to find some
> information about it, but it looks like some unreleased freescale core
> which predates e5500 core.
It looks that way yes. It was submitted at
<https://gcc.gnu.org/pipermail/gcc-patches/2009-November/273251.html>
and committed as <https://gcc.gnu.org/g:b17f98b1c541>. It looks as if
it was based on the e500mc core, while e5500 is a new core (or
significantly different anyway).
> ISA (without extensions like altivec) seems
> to be same for e500mc64, e5500 and e6500 cores and difference is only
> pipeline definitions in gcc config files. So if my understanding is
> correct then kernel binary compiled with any of these -mcpu= flag should
> work on any of those cores. Just for mismatches core binary will not be
> optimized for speed.
It appears the E500MC64 never made it outside of FSL, so it is best not
to use it at all, imo.
Segher
WARNING: multiple messages have this Message-ID (diff)
From: Segher Boessenkool <segher@kernel.crashing.org>
To: "Pali Rohár" <pali@kernel.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
Nicholas Piggin <npiggin@gmail.com>
Subject: Re: [PATCH v1] powerpc/64: Set default CPU in Kconfig
Date: Fri, 16 Dec 2022 13:15:43 -0600 [thread overview]
Message-ID: <20221216191543.GE25951@gate.crashing.org> (raw)
In-Reply-To: <20221215204202.mbw2ij4ou7t2ttpv@pali>
Hi!
On Thu, Dec 15, 2022 at 09:42:02PM +0100, Pali Rohár wrote:
> On Wednesday 07 December 2022 14:38:40 Christophe Leroy wrote:
> > default "power8" if POWER8_CPU
> > default "power9" if POWER9_CPU
> > default "power10" if POWER10_CPU
> > + default "e500mc64" if E5500_CPU
>
> Now I'm looking at this change again... and should not E5500_CPU rather
> enforce -mcpu=e5500 flag? I know that your patch moves e500mc64 flag
> from the Makefile to Kconfig, but maybe it could be changed in some
> other followup patch...
>
> Anyway, do you know what is e500mc64 core? I was trying to find some
> information about it, but it looks like some unreleased freescale core
> which predates e5500 core.
It looks that way yes. It was submitted at
<https://gcc.gnu.org/pipermail/gcc-patches/2009-November/273251.html>
and committed as <https://gcc.gnu.org/g:b17f98b1c541>. It looks as if
it was based on the e500mc core, while e5500 is a new core (or
significantly different anyway).
> ISA (without extensions like altivec) seems
> to be same for e500mc64, e5500 and e6500 cores and difference is only
> pipeline definitions in gcc config files. So if my understanding is
> correct then kernel binary compiled with any of these -mcpu= flag should
> work on any of those cores. Just for mismatches core binary will not be
> optimized for speed.
It appears the E500MC64 never made it outside of FSL, so it is best not
to use it at all, imo.
Segher
next prev parent reply other threads:[~2022-12-16 19:18 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-07 13:38 [PATCH v1] powerpc/64: Set default CPU in Kconfig Christophe Leroy
2022-12-07 13:38 ` Christophe Leroy
2022-12-08 19:13 ` Pali Rohár
2022-12-08 19:13 ` Pali Rohár
2022-12-15 20:42 ` Pali Rohár
2022-12-15 20:42 ` Pali Rohár
2022-12-16 19:15 ` Segher Boessenkool [this message]
2022-12-16 19:15 ` Segher Boessenkool
2022-12-16 22:23 ` Pali Rohár
2022-12-16 22:23 ` Pali Rohár
2022-12-16 23:02 ` Segher Boessenkool
2022-12-16 23:02 ` Segher Boessenkool
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