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

From	Stephen Warren <swarren@wwwdotorg.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 2/3] ARM: multi_v7_defconfig: Switch BCM2835 to sdhci-iproc.c for MMC
Date	2016-04-01 19:00 +0200
Message-ID	<rjaAr-7em-9@gated-at.bofh.it> (permalink)
References	<riV8m-4z1-7@gated-at.bofh.it> <riV8n-4z1-19@gated-at.bofh.it> <riWH9-5RD-25@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 03/31/2016 08:01 PM, Stephen Warren wrote:
> 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.

Ah, now I realize that sdhci-bcm2835.c and sdhci-iproc.c are two 
alternative drivers for the same HW device. For some reason I got the 
incorrect impression from some past email/patch discussion that 
sdhci-iproc.c was a driver for the alternative SD controller in the chip.

So, there's no problem with this patch.
Acked-by: Stephen Warren <swarren@wwwdotorg.org>

(although /me wonders why sdhci-iproc.c was even added in the first 
place given sdhci-bcm2835.c pre-dates it by over 2 years, and equally 
why the new driver is any faster given it looks almost identical and 
accesses the same HW, but I suppose it doesn't matter).

Thread

[PATCH 1/3] ARM: multi_v7_defconfig: Add more BCM2835 support Eric Anholt <eric@anholt.net> - 2016-04-01 02:30 +0200
  [PATCH 2/3] ARM: multi_v7_defconfig: Switch BCM2835 to sdhci-iproc.c for MMC Eric Anholt <eric@anholt.net> - 2016-04-01 02:30 +0200
    Re: [PATCH 2/3] ARM: multi_v7_defconfig: Switch BCM2835 to  sdhci-iproc.c for MMC Stephen Warren <swarren@wwwdotorg.org> - 2016-04-01 04:10 +0200
      Re: [PATCH 2/3] ARM: multi_v7_defconfig: Switch BCM2835 to sdhci-iproc.c for MMC Eric Anholt <eric@anholt.net> - 2016-04-01 17:50 +0200
      Re: [PATCH 2/3] ARM: multi_v7_defconfig: Switch BCM2835 to  sdhci-iproc.c for MMC Stephen Warren <swarren@wwwdotorg.org> - 2016-04-01 19:00 +0200
        Re: [PATCH 2/3] ARM: multi_v7_defconfig: Switch BCM2835 to  sdhci-iproc.c for MMC Stefan Wahren <stefan.wahren@i2se.com> - 2016-04-01 22:20 +0200
  Re: [PATCH 1/3] ARM: multi_v7_defconfig: Add more BCM2835 support Stephen Warren <swarren@wwwdotorg.org> - 2016-04-01 04:10 +0200

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