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

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Message-ID: <87h9flnxcu.fsf@eliezer.anholt.net>
Date:	Fri, 01 Apr 2016 08:48:49 -0700
From:	Eric Anholt <eric@...olt.net>
To:	Stephen Warren <swarren@...dotorg.org>
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

Stephen Warren <swarren@...dotorg.org> writes:

> 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.

I think you're thinking of SDHOST, the other controller?  This is just
switching implementations for the EMMC controller so that eventually we
can delete our old implementation.

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