[PATCH 2/3] ARM: multi_v7_defconfig: Switch BCM2835 to sdhci-iproc.c for MMC
phil at raspberrypi.org
Fri Apr 1 01:20:31 PDT 2016
On 01/04/2016 03:01, 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.
The Arasan MMC block uses the PLLC_PER divider output from PLLC, as
opposed to any of the PLLC_CORE outputs, so it is immune to core clock
changes - unlike the BRCM SD Host block.
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