FreeBSD on Raspberry Pi 512MB (with U-Boot + ubldr)
aoyama at peach.ne.jp
Mon Dec 3 14:51:41 UTC 2012
>>> BTW, SDHCI is not yet stable?
>> There is one issue with setting SDHCI clock. I'll commit fix later today.
> I like to share some information about the SD card reading speed.
> While exchanging the old boot sequence with then new one I once booted
> with the new boot sequence but without an /boot/loader.rc file.
> The reading speed achieved with
> dd if=/dev/mmcsd0 of=/dev/null bs=1m count=100
> from the SD card was 10 Mbyte/sec.
> After creating the file with "echo 'fdt addr 0x100' > /boot/loader.rc"
> and rebooting the reading speed achieved from the SD card was down to
> 2.8 Mbyte/sec.
> Although the SDHCI frequency was shown on the second boot as double high
> on the first (100MHz versus 50MHz) the reading speed was much lower.
> I think the cause was the mmcsd bus bit width which was reported as 4 at
> the first and as 1 at the second boot.
At this time, it must be 50. if use 100MHz, some cards cant be used anymore.
Howerver, probably 4bit transfer is OK.
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