linux-kernel - Re: [PATCH 2/3] ARM: multi_v7_defconfig: Switch BCM2835 to sdhci-iproc.c for MMC

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Message-ID: <56FDD697.2050901@wwwdotorg.org>
Date:	Thu, 31 Mar 2016 20:01:59 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Eric Anholt <eric@...olt.net>
Cc:	linux-rpi-kernel@...ts.infradead.org,
	Russell King <linux@....linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Lee Jones <lee@...nel.org>,
	Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [PATCH 2/3] ARM: multi_v7_defconfig: Switch BCM2835 to
 sdhci-iproc.c for MMC

On 03/31/2016 06:28 PM, Eric Anholt wrote:
> This approximately triples write performance for the SD card.  My card
> is too full of important data to collect very reliable numbers, but I
> see 271.361% +/- 166.742% improvement (n=3 before, 6 after), for 'dd
> if=/dev/zero of=/boot/asdf bs=1M count=3 oflag=dsync,direct'.  Read
> performance appears to be unaffected.

I thought that switching the defconfig wasn't possible, since this HW 
module relies on the SoC core clock, and that can be asynchronously 
changed by the FW running on the VideoCore. Consequently, this change 
isn't safe unless the user puts non-default options in their config.txt.

The same comment applies to "[PATCH 1/4] ARM: bcm2835: Switch BCM2835 to 
sdhci-iproc.c for MMC" in the other series.