linux-kernel - Re: [PATCH v2 3/3] spi: spi-davinci: convert to DMA engine API

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Date:	Wed, 22 Aug 2012 09:15:22 +0530
From:	Vinod Koul <vinod.koul@...ux.intel.com>
To:	Matt Porter <mporter@...com>
Cc:	cjb@...top.org, grant.likely@...retlab.ca,
	Linux DaVinci Kernel List 
	<davinci-linux-open-source@...ux.davincidsp.com>,
	Sekhar Nori <nsekhar@...com>,
	Linux MMC List <linux-mmc@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux SPI Devel List 
	<spi-devel-general@...ts.sourceforge.net>,
	Linux ARM Kernel List <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 3/3] spi: spi-davinci: convert to DMA engine API

On Tue, 2012-08-21 at 14:43 -0400, Matt Porter wrote:
> Removes use of the DaVinci EDMA private DMA API and replaces
> it with use of the DMA engine API.
> 
> Signed-off-by: Matt Porter <mporter@...com>
> ---

> +		struct dma_slave_config dma_rx_conf = {
> +			.direction = DMA_DEV_TO_MEM,
> +			.src_addr = (unsigned long)dspi->pbase + SPIBUF,
> +			.src_addr_width = data_type,
> +			.src_maxburst = 1,
what does 1 mean in this context? We define as number of units that
needs to be transfered, so are you sure that you want only one unit to
be dma'ed in a single burst. that seems like killing your dmac,
shouldn't you be using larger bursts for a better dma performance?


-- 
~Vinod

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