SD card compatibility problem

[hyobokahn]

Hello.

I'm working on Yocto 4.1.15-1.0.0 ga release with  i.MX6 Solo and custom board.

Now I have SD cad compatibility problem with SD2 channel of i.MX6 Solo.

I have 4 SD memory cards. two of them working fine, but two are fail.

The working SD memory card was

   Transcend Class 10 30MB/s 200x 16GB & Secure Digital 66X ULTIMA II 1GB

The fail SD memory card was

   Transcend Class 10 8GB & Transcend Class 6 4GB

It looks like low speed device is not working.

is there any problem in default device driver?

or, need I fix driver source to support it myself?

then where I must fix it?

I do not change any SD/MMC driver and device tree on Linux 4.1.15 from Yocto build.

Just enable device tree and add to support card detect GPIO pin for SD2 interface.

please give me any idea to fix this problem.

Thanks.

[igorpadykov]

Hi Hyobok 

this may be signal integrity issue so one can tweak drive strength of sd signals
using pad control registers, like IOMUXC_SW_PAD_CTL_PAD_SD3_DATA2.
and in dts file one can look at entries like
&usdhc3 {     pinctrl-names = "default", "state_100mhz", "state_200mhz";
http://git.freescale.com/git/cgit.cgi/imx/linux-imx.git/tree/arch/arm/boot/dts/imx6qdl-sabreauto.dts...

Best regards
igor
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