DESK-MX6-L/Peripherals/SD

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History
Issue Date Notes

2021/07/16

First DESK-MX6-L release

2022/03/03

DESK-MX6-L 3.0.0 release
2023/04/11 DESK-MX6-L 4.0.0 release


Peripheral SD[edit | edit source]

Device tree configuration[edit | edit source]

Here below an example of device tree configuration used on standard DAVE's kit for the AXELLite SOM:

From imx6qdl-sbcx-revb-common.dtsi:

&usdhc1 {
    pinctrl-names = "default";
    pinctrl-0 = <&pinctrl_usdhc1_sbcx>;
    no-1-8-v;
    keep-power-in-suspend;
    enable-sdio-wakeup;
    cd-gpios = <&gpio3 19 GPIO_ACTIVE_LOW>; /* GPIO3_19 */
    status = "okay";
};
...
...
&iomuxc {
...
...
    usdhc1 {
        pinctrl_usdhc1_sbcx: usdhc1grp-1{
            fsl,pins = <
                MX6QDL_PAD_SD1_CMD__SD1_CMD    0x17060
                MX6QDL_PAD_SD1_CLK__SD1_CLK    0x10060
                MX6QDL_PAD_SD1_DAT0__SD1_DATA0 0x17060
                MX6QDL_PAD_SD1_DAT1__SD1_DATA1 0x17060
                MX6QDL_PAD_SD1_DAT2__SD1_DATA2 0x17060
                MX6QDL_PAD_SD1_DAT3__SD1_DATA3 0x17060
                /* card detect */
                MX6QDL_PAD_EIM_D19__GPIO3_IO19  0x1b0b0
            >;
        };
    };
...
...
};

The USDHC interface is re-configured on carrier device tree because of the Card Detect pin (which is related to the real board hardware implementation).

Accessing the peripheral[edit | edit source]

Once initialized, the SD device is mapped to the standard /dev/mmcblk0pX block device, depending on how many partition are created on the SD card.

Linux messages at boot time[edit | edit source]

If the microSd card is inserted at boot time, the kernel - once the USDHC interface has been initialized - prints the device information and the partition detected like p1, p2, etc.:

...
...
[    4.561266] sdhci: Secure Digital Host Controller Interface driver
[    4.567479] sdhci: Copyright(c) Pierre Ossman
[    4.571840] sdhci-pltfm: SDHCI platform and OF driver helper
[    4.615639] mmc0: SDHCI controller on 2190000.mmc [2190000.mmc] using ADMA
[    4.664698] mmc0: host does not support reading read-only switch, assuming write-enable
[    4.681355] mmc0: new high speed SDHC card at address aaaa
[    4.687736] mmcblk0: mmc0:aaaa SL32G 29.7 GiB 
...
...
[    4.710742]  mmcblk0: p1 p2
[    5.294335] EXT4-fs (mmcblk0p2): mounting ext3 file system using the ext4 subsystem
[    5.343233] EXT4-fs (mmcblk0p2): mounted filesystem with ordered data mode. Opts: (null). Quota mode: none.
[    8.611380] EXT4-fs (mmcblk0p2): re-mounted. Opts: (null). Quota mode: none.
...
...

Additional information[edit | edit source]

If the root file system configuration does not automatically mount the partition, it is possible to mount the device using the following command:

root@desk-mx6:~# mkdir -p /mnt/boot
root@desk-mx6:~# mkdir -p /mnt/rfs
root@desk-mx6:~# mount /dev/mmcblk0p1 /mnt/boot
root@desk-mx6:~# mount /dev/mmcblk0p2 /mnt/rfs
root@desk-mx6:~#

and then the mounted partition are available on the /mnt/boot and /mnt/rfs root file system directories.