From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ulf Hansson <ulf.hansson@linaro.org>
Subject: Re: [PATCH 07/17] mmc: sdhci: avoid unnecessary mapping/unmapping of
 align buffer
Date: Mon, 21 Dec 2015 11:28:15 +0100
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To: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Marcin Wojtas <mw@semihalf.com>, Gregory CLEMENT <gregory.clement@free-electrons.com>, Shawn Guo <shawnguo@kernel.org>, Sascha Hauer <kernel@pengutronix.de>, linux-mmc <linux-mmc@vger.kernel.org>

On 19 December 2015 at 21:30, Russell King <rmk+kernel@arm.linux.org.uk> wrote:
> Unnecessarily mapping and unmapping the align buffer for SD cards is
> expensive: performance measurements on iMX6 show that this gives a hit
> of 10% on hdparm buffered disk reads.
>
> MMC/SD card IO comes from the mm/vfs which gives us page based IO, so
> for this case, the align buffer is not going to be used.  However, we
> still map and unmap this buffer.

What about the SDIO case? How will this change affect SDIO data transfers?

>
> Eliminate this by switching the align buffer to be a DMA coherent
> buffer, which needs no DMA maintanence to access the buffer.

/s/maintanence/maintenance

[...]

Kind regards
Uffe