linux-kernel - Re: [PATCH] avr32: fix build error in atstk1006

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Date:	Tue, 16 Oct 2012 18:30:50 +0800
From:	Josh Wu <josh.wu@...el.com>
To:	Hans-Christian Egtvedt <egtvedt@...fundet.no>
CC:	linux-kernel@...r.kernel.org, hskinnemoen@...il.com,
	linux-mtd@...ts.infradead.org, dedekind1@...il.com,
	fengguang.wu@...el.com
Subject: Re: [PATCH] avr32: fix build error in atstk1006_defconfig

On 10/16/2012 5:17 PM, Hans-Christian Egtvedt wrote:
> Around Tue 16 Oct 2012 15:19:27 +0800 or thereabout, Josh Wu wrote:
>> fixed the following compile error when use avr32 atstk1006_defconfig:
>>    drivers/mtd/nand/atmel_nand.c: In function 'pmecc_err_location':
>>    drivers/mtd/nand/atmel_nand.c:639: error: implicit declaration of function 'writel_relaxed'
>>
>> which was introduced by commit 1c7b874d33b463 ("mtd: at91: atmel_nand: add Programmable Multibit ECC controller support").
>> The PMECC for nand flash code uses writel_relaxed(). But in avr32, there is no macro "writel_relaxed" defined. This patch add writex_relaxed macro definitions.
>>
>> Signed-off-by: Josh Wu <josh.wu@...el.com>
>> ---
>>   arch/avr32/include/asm/io.h |    4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/arch/avr32/include/asm/io.h b/arch/avr32/include/asm/io.h
>> index cf60d0a..fc6483f 100644
>> --- a/arch/avr32/include/asm/io.h
>> +++ b/arch/avr32/include/asm/io.h
>> @@ -165,6 +165,10 @@ BUILDIO_IOPORT(l, u32)
>>   #define readw_be			__raw_readw
>>   #define readl_be			__raw_readl
>>   
>> +#define writeb_relaxed			writeb
>> +#define writew_relaxed			writew
>> +#define writel_relaxed			writel
>> +
> I'm wondering if they should be something similar to SH arch:
>
> #define writeb_relaxed(v,c) ((void)__raw_writeb((__force u8)ioswabb(v),c))
>
> What is the intention behind the macro? Which restriction is relaxed?

According to my understanding, the xxx_relaxed() is that I/O function 
without any memory barriers. for Multi-cpu, the execute order are less 
limited.
So the relaxed write function should be more effective than non-relaxed one.

But for single cpu, relaxed function should work same as non-relaxed 
function.
Please correct me if I'm understand in a wrong way.

Best Regards,
Josh Wu

>
>>   #define writeb_be			__raw_writeb
>>   #define writew_be			__raw_writew
>>   #define writel_be			__raw_writel

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