Monday, November 4, 2013

SD card reader not working in Linux

One thing I've not been able to get working in Linux is the SD card reader on my laptop. The Ubuntu manual sdhci driver page hints at why:
Many of existing SD controller chips have some nonstandard requirements, proprietary registers and hardware bugs, requiring additional handling. 
lspci reveals the name of the SD card reader:
SD Host controller: O2 Micro, Inc. Integrated MMC/SD Controller (rev 01)
dmesg that there's a problem:
mmc0: Unknown controller version (16). You may experience problems.
This is a message I've noticed while the computer is booting, I think for as long as I've used Linux, and in many different distributions.

There are several bug reports for this issue, but I haven't found any "additional handling". To read and write to SD cards, I use a USB card reader from PoundWorld.

One post I came across suggested there might be a fix coming in kernel 3.5, but I'm using 3.10 from Wheezy backports.

In the end I came across a way to disable the SD card driver so that the error message doesn't appear. Add:
blacklist sdhci-pci 
blacklist sdhci 
blacklist mmc_core 
to /etc/modprobe.d/blacklist.conf.

This didn't take effect until I ran:
update-initramfs -u 
Debian forum.

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