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

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Date:   Tue, 4 Jun 2019 17:18:08 +1000
From:   Greg Ungerer <gerg@...ux-m68k.org>
To:     Angelo Dureghello <angelo@...am.it>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     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 Angelo,

On 3/6/19 10:26 pm, Angelo Dureghello wrote:
> 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 ?

I'll add it to the m68knommu git tree.
Seeing as you wrote it Geert I assume you have no problem with that?  :-)

Regards
Greg


> 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
>>
>