linux-kernel - Re: [PATCH v2 2/2] spi: omap2-mcspi: Add FIFO buffer support

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Date:	Wed, 12 Jun 2013 16:47:55 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Illia Smyrnov <illia.smyrnov@...com>
Cc:	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Rob Landley <rob@...dley.net>, Daniel Mack <zonque@...il.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Tony Lindgren <tony@...mide.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	devicetree-discuss@...ts.ozlabs.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	spi-devel-general@...ts.sourceforge.net, linux-omap@...r.kernel.org
Subject: Re: [PATCH v2 2/2] spi: omap2-mcspi: Add FIFO buffer support

On Tue, Jun 11, 2013 at 08:09:15PM +0300, Illia Smyrnov wrote:
> The MCSPI controller has a built-in FIFO buffer to unload the DMA or interrupt
> handler and improve data throughput. This patch adds FIFO buffer support for SPI
> transfers in DMA mode.

> The FIFO could be enabled for SPI module by setting up the "ti,spi-fifo-enabled"
> configuration parameter in DT.
> If FIFO enabled, the largest possible FIFO buffer size will be calculated and
> setup for each SPI transfer. Even if the FIFO is enabled in DT, it won't be used
> for the SPI transfers when: calculated FIFO buffer size is less then 2 bytes or
> the FIFO buffer size isn't multiple of the SPI word length.

Why is the default to disable the FIFO?

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