DESK-MX8M-L/Peripherals/SD
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| Version | Issue Date | Notes | |
| 1.0.0 | Jan 2022 | First DESK-MX8M release | |
Contents
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 ORCA SOM:
From imx8mp-mito8mplus-cb1001.dts:
&usdhc2 {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_usdhc2>, <&pinctrl_usdhc2_gpio>;
cd-gpios = <&gpio2 12 GPIO_ACTIVE_LOW>;
bus-width = <4>;
status = "okay";
};
From imx8mp-mito8mplus-cb1001.dts:
&iomuxc {
...
...
pinctrl_usdhc2_gpio: usdhc2grp-gpio {
fsl,pins = <
MX8MP_IOMUXC_SD2_CD_B__GPIO2_IO12 0x1c4
>;
};
pinctrl_usdhc2: usdhc2grp {
fsl,pins = <
MX8MP_IOMUXC_SD2_CLK__USDHC2_CLK 0x190
MX8MP_IOMUXC_SD2_CMD__USDHC2_CMD 0x1d0
MX8MP_IOMUXC_SD2_DATA0__USDHC2_DATA0 0x1d0
MX8MP_IOMUXC_SD2_DATA1__USDHC2_DATA1 0x1d0
MX8MP_IOMUXC_SD2_DATA2__USDHC2_DATA2 0x1d0
MX8MP_IOMUXC_SD2_DATA3__USDHC2_DATA3 0x1d0
>;
};
...
...
};
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.:
... ... [ 1.283284] sdhci: Secure Digital Host Controller Interface driver [ 1.289476] sdhci: Copyright(c) Pierre Ossman [ 1.300935] sdhci-pltfm: SDHCI platform and OF driver helper [ 1.342624] mmc0: SDHCI controller on 30b40000.mmc [30b40000.mmc] using ADMA [ 1.388722] mmc2: SDHCI controller on 30b60000.mmc [30b60000.mmc] using ADMA ... [ 1.618036] mmcblk2: mmc2:0001 DG4008 7.28 GiB [ 1.622685] mmcblk2boot0: mmc2:0001 DG4008 partition 1 4.00 MiB [ 1.628729] mmcblk2boot1: mmc2:0001 DG4008 partition 2 4.00 MiB [ 1.635352] mmcblk2rpmb: mmc2:0001 DG4008 partition 3 4.00 MiB, chardev (237:0) [ 1.644839] mmcblk2: p1 p2 p3 ... [ 2.382461] sdhci-esdhc-imx 30b50000.mmc: Got CD GPIO [ 2.418293] mmc1: SDHCI controller on 30b50000.mmc [30b50000.mmc] using ADMA [ 2.505677] mmc1: new high speed SDHC card at address aaaa [ 2.514258] mmcblk1: mmc1:aaaa SA16G 14.8 GiB [ 2.527325] mmcblk1: p1 p2 ... ... [ 3.245015] EXT4-fs (mmcblk1p2): mounted filesystem with ordered data mode. Opts: (null) [ 4.792069] EXT4-fs (mmcblk1p2): re-mounted. Opts: (null)
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-mx8mp:~# mkdir -p /mnt/boot root@desk-mx8mp:~# mkdir -p /mnt/rfs root@desk-mx8mp:~# mount /dev/mmcblk0p1 /mnt/boot root@desk-mx8mp:~# mount /dev/mmcblk0p2 /mnt/rfs root@desk-mx8mp:~#
and then the mounted partition are available on the /mnt/boot and /mnt/rfs root file system directories.
