linux-kernel - Re: [PATCH v2] sh: Remove IO memcpy and memset from sh code

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Message-ID: <CAMuHMdXnfsJ9K=6q5YzTUS=etjQvAWQqbNksaMkysX9bJtMRwA@mail.gmail.com>
Date: Thu, 30 Jan 2025 11:18:32 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Julian Vetter <julian@...er-limits.org>
Cc: Arnd Bergmann <arnd@...db.de>, Yoshinori Sato <ysato@...rs.sourceforge.jp>, 
	Rich Felker <dalias@...c.org>, John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>, linux-sh@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] sh: Remove IO memcpy and memset from sh code

Hi Julian,

On Tue, 28 Jan 2025 at 16:22, Julian Vetter <julian@...er-limits.org> wrote:
> Remove IO memcpy and memset from sh specific code and fall back to the
> new implementations from lib/iomem_copy.c. They use word accesses if the
> buffers are aligned and only fall back to byte accesses for potentially
> unaligned parts of a buffer.
>
> Signed-off-by: Julian Vetter <julian@...er-limits.org>
> ---
> Changes for V2:
> - Removed also SH4 specific memcpy_fromio code

Thanks for the update!

> --- a/arch/sh/kernel/io.c
> +++ /dev/null
> @@ -1,111 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0
> -/*
> - * arch/sh/kernel/io.c - Machine independent I/O functions.
> - *
> - * Copyright (C) 2000 - 2009  Stuart Menefy
> - * Copyright (C) 2005  Paul Mundt
> - */
> -#include <linux/module.h>
> -#include <linux/pci.h>
> -#include <asm/machvec.h>
> -#include <asm/io.h>
> -
> -/*
> - * Copy data from IO memory space to "real" memory space.
> - */
> -void memcpy_fromio(void *to, const volatile void __iomem *from, unsigned long count)
> -{

[...]

> -       mb();
> -}
> -EXPORT_SYMBOL(memcpy_fromio);
> -
> -/*
> - * Copy data from "real" memory space to IO memory space.
> - */
> -void memcpy_toio(volatile void __iomem *to, const void *from, unsigned long count)
> -{

[...]

> -
> -       mb();
> -}
> -EXPORT_SYMBOL(memcpy_toio);

LGTM. My only worry is the removal of the mb() calls, cfr. the
scary warning at
https://elixir.bootlin.com/linux/v6.13/source/arch/sh/include/asm/barrier.h#L13

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds