I followed the instruction here https://forum.openwrt.org/viewtopic.php?id=37746

I used to get error -16 in the link above but it went away after I removed the led and buttons module. It turned out that GPIO 0 was used by something else and hence the error -16 error.

And here is my dmesg log:

[   57.680000] gpio-mmc: Failed to request mmc_spi module.
[   57.700000] spi-gpio spi-gpio.0: master is unqueued, this is deprecated
[   57.710000] gpio-mmc: MMC-Card "default" attached to GPIO pins di=9, do=13, clk=8, cs=0

It looks like it does not do anything further to detect my SD card. I'm using Sandisk class 2 2GB microSD card which should be fine for this purpose.

I also noticed this in my dmesg log which could have hampered my effort:

[   34.760000] mmc_spi: Unknown symbol mmc_spi_get_pdata (err 0)
[   34.770000] mmc_spi: Unknown symbol mmc_spi_put_pdata (err 0)

My soldering should be fine and I have ensured that my GPIO pins that are relevant to my SD card data transfer are not used by something else.

I'm running revision r36713.

Any idea on the problem?

Thank you :-)