linux-kernel - Re: [PATCH] m68k: io: Fix io{read,write}{16,32}be() for Coldfire peripherals

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Date:   Mon, 3 Jun 2019 14:26:08 +0200
From:   Angelo Dureghello <angelo@...am.it>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Greg Ungerer <gerg@...ux-m68k.org>,
        Logan Gunthorpe <logang@...tatee.com>,
        Arnd Bergmann <arnd@...db.de>, linux-m68k@...ts.linux-m68k.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] m68k: io: Fix io{read,write}{16,32}be() for Coldfire
 peripherals

Hi Greg (and all),

couldn't seen any follow up on this patch. I tested it and at least
for mcf5441x it works properly and solves all issues.

Do you think it may be accepted as an initial fix ?

Regards,
Angelo

On Mon, Apr 29, 2019 at 10:19:37AM +0200, Geert Uytterhoeven wrote:
> The generic definitions of mmio_{read,write}{16,32}be() in lib/iomap.c
> assume that the {read,write}[wl]() I/O accessors always use little
> endian accesses, and swap the result.
> 
> However, the Coldfire versions of the {read,write}[wl]() I/O accessors are
> special, in that they use native big endian instead of little endian for
> accesses to the on-SoC peripheral block, thus violating the assumption.
> 
> Fix this by providing our own variants, using the raw accessors,
> reinstating the old behavior.  This is fine on m68k, as no special
> barriers are needed, and also avoids swapping data twice.
> 
> Reported-by: Angelo Dureghello <angelo@...am.it>
> Fixes: aecc787c06f4300f ("iomap: Use non-raw io functions for io{read|write}XXbe")
> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> ---
> This can be reverted later, after this oddity of the Coldfire I/O
> support has been fixed, and drivers have been updated.
> ---
>  arch/m68k/include/asm/io.h | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/m68k/include/asm/io.h b/arch/m68k/include/asm/io.h
> index aabe6420ead2a599..d47e7384681ab1cd 100644
> --- a/arch/m68k/include/asm/io.h
> +++ b/arch/m68k/include/asm/io.h
> @@ -8,6 +8,12 @@
>  #include <asm/io_mm.h>
>  #endif
>  
> +#define mmio_read16be(addr)		__raw_readw(addr)
> +#define mmio_read32be(addr)		__raw_readl(addr)
> +
> +#define mmio_write16be(val, port)	__raw_writew((val), (port))
> +#define mmio_write32be(val, port)	__raw_writel((val), (port))
> +
>  #include <asm-generic/io.h>
>  
>  #endif /* _M68K_IO_H */
> -- 
> 2.17.1
>