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From: Rob Landley <>
To: Arnd Bergmann <>,
Cc: Linus Torvalds <>,
	Vineet Gupta <>, Arnd Bergmann <>,
	Yoshinori Sato <>,
	Rich Felker <>,,
Subject: Re: [RFC 03/12] sh: remove unaligned access for sh4a
Date: Mon, 10 May 2021 16:11:03 -0500	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 5/7/21 5:07 PM, Arnd Bergmann wrote:
> From: Arnd Bergmann <>
> Unlike every other architecture, sh4a uses an inline asm implementation
> for get_unaligned(). I have shown that this produces better object
> code than the asm-generic version. However, there are very few users of
> arch/sh/ overall, and most of those seem to use sh4 rather than sh4a CPU

Hitachi's sh4, sh3, and sh2 are all out of patent, and have been cloned as open
hardware. (Modulo the sh4 clone uses a different mmu design, but lots of
regression testing gets done against qemu-system-sh4 and sh4 hardware using the
original mmu.) Plus superh was the bestselling CPU architecture in the world for
3 years back in the 1990s, and there's a remaining userbase from that.

sh5 and the "a" designs like sh4a were created by renesas after hitachi spun off
the IP to them, and are not out of patent. I do not have access to an sh4a test

> Signed-off-by: Arnd Bergmann <>
> ---
>  arch/sh/include/asm/unaligned-sh4a.h | 199 ---------------------------
>  arch/sh/include/asm/unaligned.h      |  13 --

All I can test is that it didn't cause regressions on my sh4 and j-core systems,
which it (unsurprisingly) did not.

Acked-by: Rob Landley <>


  reply	other threads:[~2021-05-10 20:55 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-07 22:07 [RFC 0/12] Unify asm/unaligned.h around struct helper Arnd Bergmann
2021-05-07 22:07 ` [RFC 03/12] sh: remove unaligned access for sh4a Arnd Bergmann
2021-05-10 21:11   ` Rob Landley [this message]
2021-05-07 22:07 ` [RFC 0/12] Unify asm/unaligned.h around struct helper Arnd Bergmann

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