Opened 7 years ago

Last modified 4 years ago

#9292 new defect

Terrible transfer speeds using mmc-over-gpio, 50x lower than in 8.09.2 (DIR-300)

Reported by: dark_skeleton <dark.skeleton@…> Owned by: developers
Priority: high Milestone: Chaos Calmer 15.05
Component: kernel Version: Backfire 10.03.1 RC4
Keywords: mmc-over-gpio spi-bitbang mmc sd card gpio slow Cc:


I just flashed 10.03.1-rc5-testing to confirm it's still the same as in rc4, and yes - it hasn't been fixed.

In 8.09.2 after making the SD/MMC card mod to DIR-300 (, I was getting quite low, but usable transfer speeds - around 20-30kB/s (and of course 100% CPU usage). However in every version of 10.03.1-rcX I'm getting only around 0.5kB/s. Yes, half a kilobyte per second - measured with a stopwatch, using dd on a vfat partition. Not to mention that mounting a partition takes around one minute now, and listing it takes around two minutes. The speed on ext3 partition is even worse - 0.32kB/s. (CPU usage at 100% by the driver)

This is ridiculous, there must be something wrong with it. CPU usage is 100% and unless my CPU speed just magically went down around 50 times, this needs to be fixed!.

Attachments (0)

Change History (2)

comment:1 Changed 6 years ago by LongHairedHacker

A possible cause or this problem is that the default value or max_bus_speed is set to 5 mhz (5000000hz). It least that's the case on my dir300 running backfire 10.3.1.

As suggested in, I added echo 25000000 > $dir/max_bus_speed to the /etc/init.d/mmc_over_gpio script, just before the echo 1 > $dir/register line.

Performance Read/Write seems slightly improved, (did not measure it yet) but still cpu usage is really high in some situations, causing ssh sessions to freeze for some seconds.
I'm new to openwrt and unfamiliar with older versions, so I don't know what to expect.


comment:2 Changed 4 years ago by jow

  • Milestone changed from Backfire 10.03.2 to Chaos Calmer (trunk)

Milestone Backfire 10.03.2 deleted

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