Message-ID: <50873BFF.4070508@yahoo.es>
Date: Wed, 24 Oct 2012 08:53:19 +0800
From: Hein Tibosch <hein_tibosch@yahoo.es>
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To: Andrew Morton <akpm@linux-foundation.org>
CC: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        viresh kumar <viresh.kumar@linaro.org>,
        spear-devel <spear-devel@list.st.com>,
        Hans-Christian Egtvedt <egtvedt@samfundet.no>,
        Arnd Bergmann <arnd.bergmann@linaro.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "ludovic.desroches" <ludovic.desroches@atmel.com>,
        Havard Skinnemoen <havard@skinnemoen.net>,
        Nicolas Ferre <nicolas.ferre@atmel.com>
Subject: Re: [PATCH REGRESSION FIX] dw_dmac: make driver's endianness configurable
References: <507A6FA5.1000800@yahoo.es> <20121023161218.45a7ae4e.akpm@linux-foundation.org>
In-Reply-To: <20121023161218.45a7ae4e.akpm@linux-foundation.org>
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Hi Andrew,

On 10/24/2012 7:12 AM, Andrew Morton wrote:
> On Sun, 14 Oct 2012 15:54:13 +0800
> Hein Tibosch <hein_tibosch@yahoo.es> wrote:
>
>> The dw_dmac was originally developed for avr32 to be used with the Synopsys
>> DesignWare AHB DMA controller. Starting from 2.6.38, access to the device's i/o
>> memory was done with the little-endian readl/writel functions(1)
>>
>> This broke the driver for the avr32 platform, because it needs big (native)
>> endian accessors.
>> This patch makes the endianness configurable using 'DW_DMAC_BIG_ENDIAN_IO',
>> which will default be true for AVR32
> Do we think this bug should be fixed in earlier kernel versions?
>
> If so, the patch might need to be tweaked for 3.6 and earlier, which
> don't have the dma_read_byaddr() definition.

The 'bug' only affected avr32 (AP700x) users. I think there won't be much demand
for it. Beside that, there were more breakages after 2.6.38, which have only
recently been fixed in 3.7-rc1

These patches should then be back-ported as well:

 http://www.spinics.net/lists/linux-mmc/msg16104.html
 http://www.gossamer-threads.com/lists/linux/kernel/1603537

Thanks, Hein
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