linux-kernel - Re: [PATCH 1/2] dw_dmac: make driver endianness configurable

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Message-ID: <20120827070323.GC28721@samfundet.no>
Date:	Mon, 27 Aug 2012 09:03:23 +0200
From:	Hans-Christian Egtvedt <egtvedt@...fundet.no>
To:	Hein Tibosch <hein_tibosch@...oo.es>
Cc:	viresh kumar <viresh.kumar@...aro.org>,
	spear-devel <spear-devel@...t.st.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"ludovic.desroches" <ludovic.desroches@...el.com>,
	Havard Skinnemoen <havard@...nnemoen.net>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arnd Bergmann <arnd.bergmann@...aro.org>
Subject: Re: [PATCH 1/2] dw_dmac: make driver endianness configurable

Around Mon 27 Aug 2012 04:53:02 +0800 or thereabout, Hein Tibosch wrote:
> The dw_dmac was originally developed for avr32 to be used with the
> Synopsys DesignWare AHB DMA controller. After 2.6.38, device access was done
> with the little-endian readl/writel functions. This didn't work on the
> avr32 platform, because it needs native-endian (i.e. big-endian) accessors.
> This patch makes the endianness configurable using 'DW_DMAC_BE',
> which will default be true for AVR32

I think the English in kconfig could use some brushing up.

> Signed-off-by: Hein Tibosch <hein_tibosch@...oo.es>
> ---
>  drivers/dma/Kconfig        |    8 ++++++++
>  drivers/dma/dw_dmac_regs.h |   23 +++++++++++++++++++++++
>  2 files changed, 31 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
> index aadeb5b..3635daf 100644
> --- a/drivers/dma/Kconfig
> +++ b/drivers/dma/Kconfig
> @@ -89,6 +89,14 @@ config DW_DMAC
>  	  Support the Synopsys DesignWare AHB DMA controller.  This
>  	  can be integrated in chips such as the Atmel AT32ap7000.
>  
> +config DW_DMAC_BE
>

This name isn't that long, so we could skip the abbreviation of big endian;
DW_DMAC_BIG_ENDIAN_IO or something similar?

> +	bool "Synopsys DesignWare AHB DMA needs big endian access"
>

bool "Use big endian I/O register access"

> +	default y if AVR32
> +	depends on DW_DMAC
> +	help
> +	  Say yes if access to the Synopsys DesignWare AHB DMA controller
> +	  should be big endian, such as for Atmel AT32ap7000
> +

"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."

<snipp patch diff>

-- 
mvh
Hans-Christian Egtvedt
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