Message-ID: <503B8B26.3050205@yahoo.es>
Date: Mon, 27 Aug 2012 22:58:46 +0800
From: Hein Tibosch <hein_tibosch@yahoo.es>
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To: Hans-Christian Egtvedt <egtvedt@samfundet.no>
CC: viresh kumar <viresh.kumar@linaro.org>,
        spear-devel <spear-devel@list.st.com>,
        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>,
        Andrew Morton <akpm@linux-foundation.org>,
        Arnd Bergmann <arnd.bergmann@linaro.org>
Subject: Re: [PATCH 1/2] dw_dmac: make driver endianness configurable
References: <503A8CAE.6050606@yahoo.es> <20120827070323.GC28721@samfundet.no> <503B342C.9060300@yahoo.es> <20120827111431.GA27868@samfundet.no>
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On 8/27/2012 7:14 PM, Hans-Christian Egtvedt wrote:
> Around Mon 27 Aug 2012 16:47:40 +0800 or thereabout, Hein Tibosch wrote:
>> On 8/27/2012 3:03 PM, Hans-Christian Egtvedt wrote:
>>> Brushing up the config items:
>>>
>>> +config DW_DMAC_BIG_ENDIAN_IO
>>> +	bool "Use big endian I/O register access"
>>> +	default y if AVR32
>>> +	depends on DW_DMAC
>>> +	help
>>> +	  Say yes here to use big endian I/O access when reading and writing
>>> +	  to the DMA controller registers. This is needed on some platforms,
>>> +	  like the Atmel AVR32 architecture.
>>> +
>>> +	  If unsure, use the default setting.
> This sounds good in my ears, but I don't speak English natively.
I think you Norwegians are doing very well in English
And btw, I'm not from .es but from .nl, which is very close to England

>> And as I'd like to define the maximum memory transfer width in the same
>> Kconfig:
>>
>> +config DW_DMAC_MEM_64_BIT
>> +	bool "Allow 64-bit memory transfers"
>> +	default y if !AVR32
>> +	depends on DW_DMAC
>> +	help
>> +	  Say yes if the DMA controller may do 64-bit memory transfers
>> +	  For AVR32, say no because only up to 32-bit transfers are
>> +	  defined
> Is this sane to add? Could some non-AVR32 platforms use 64-bit and 32-bit
> depending on runtime configuration? E.g. if you build a kernel with support
> for multiple boards/processors, and there is a mix of 32-bit and 64-bit wide
> DMA support.
>
> I think it is better to select 32/64-bit at runtime.

I did that in the first patch, adding a new property to the dw_dma_slave
structure. It had the small disadvantage that some arch code had to be
adapted (at32ap700x.c).

Viresh, what do you think? Add a property called "mem_64_bit_access" or so?

Or should it be passed as a member of 'dw_dma_platform_data', because it
is a property of the (entire) DMA controller?

Hein
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