From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek Vasut Subject: Re: [PATCH] i2c: mxs: Add PIO and mixed-DMA support Date: Thu, 22 Nov 2012 01:50:37 +0100 Message-ID: <201211220150.37462.marex@denx.de> References: <1353477088-9660-1-git-send-email-marex@denx.de> Mime-Version: 1.0 Content-Type: Text/Plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1353477088-9660-1-git-send-email-marex-ynQEQJNshbs@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Cc: Fabio Estevam , Shawn Guo , Wolfram Sang List-Id: linux-i2c@vger.kernel.org Dear Marek Vasut, > Add support for the PIO mode and mixed PIO/DMA mode support. The mixed > PIO/DMA is the default mode of operation. This shall leverage overhead > that the driver creates due to setting up DMA descriptors even for very > short transfers. > > The current boundary between PIO/DMA 8 bytes, transfers shorter than 8 > bytes are transfered by PIO, longer transfers use DMA. The performance > of write transfers remains unchanged, while there is a minor improvement > of read performance. Reading 16KB EEPROM with DMA-only operations gives > a read speed of 39.5KB/s, while with then new mixed-mode the speed is > blazing 40.6KB/s. > > Signed-off-by: Marek Vasut > Cc: Fabio Estevam > Cc: Shawn Guo > Cc: Wolfram Sang [...] btw. Wolfram, you might want to drop me some credit into the MX28 i2c driver, I suspect most of the code in there is mine now anyway :-D Best regards, Marek Vasut