linux-kernel - Re: [PATCH v2 03/13] sh: remove unaligned access for sh4a

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Message-ID: <3d70eb2a-2969-197e-63e8-f3e0a6a8ddd8@physik.fu-berlin.de>
Date:   Fri, 14 May 2021 12:34:32 +0200
From:   John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To:     Arnd Bergmann <arnd@...nel.org>, linux-arch@...r.kernel.org
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Vineet Gupta <vgupta@...opsys.com>,
        Arnd Bergmann <arnd@...db.de>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>, linux-sh@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 03/13] sh: remove unaligned access for sh4a

Hi Arnd!

On 5/14/21 12:00 PM, Arnd Bergmann wrote:
> 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
> cores, so it seems not worth keeping the complexity in the architecture
> independent code.

My Renesas SH4-Boards actually run an sh4a-Kernel, not an sh4-Kernel:

root@...pitz:~> uname -a
Linux tirpitz 5.11.0-rc4-00012-g10c03c5bf422 #161 PREEMPT Mon Jan 18 21:10:17 CET 2021 sh4a GNU/Linux
root@...pitz:~>

So, if this change reduces performance on sh4a, I would rather not merge it.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@...ian.org
`. `'   Freie Universitaet Berlin - glaubitz@...sik.fu-berlin.de
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