MultiMediaCard

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Instructions to use the MultiMediaCard (MMC/SD) on your Armadeus board

Introduction

You can use standard MMC/SD/miniSD/microSD cards with your Armadeus board:

All needed drivers are included in the standard Armadeus Linux image.

Card insertion

You should see something like that on the Linux console:

 # imx-mmc imx-mmc.0: card inserted
 mmc0: host does not support reading read-only switch. assuming write-enable.
 mmc0: new SD card at address 01b0
 mmcblk0: mmc0:01b0 SD512 500224KiB
  mmcblk0: p1

Mounting the MMC/SD from Linux

  • Just mount the MMC like you will do on your PC:
 # mount /dev/mmcblk0p1 /media/mmc             (on all APF *except* APF6)
 # mount /dev/mmcblk1p1 /media/mmc             (on APF6)
  • Then, you can access the MMC's files from the /media/mmc directory. Filesystem should be automagically detected.
  • Of course if you have several partitions on your MMC/SD they will be named p1/p2/p3...
  • If you have problems with vfat code page, include the missing code page into the kernel.

Booting from MMC/SD

When your rootfs is too big to be put on the APF Flash, you can always use a MMC/SD like a Hard Drive and boot from it (this is possible because standard Armadeus kernel is compiled with the MMC driver built in).

Prepare your card

  • On your APF board (to avoid to crash your Host HD), create a good partition table on MMC (X is the id of the device, for example 1 on APF6):
 # /sbin/fdisk /dev/mmcblkX

 Delete all existing partion with 'd'
 Create a primary partion: 'n' then 'p' then '1' then 2x'ENTER'
 Change bootflag to Linux: 't' then '83'
 Save partition table: 'w'
 (To quit without saving: 'm')
  • If your APF has the mkfs tools, then format your MMC:
 # mkfs.ext4 -O ^64bit /dev/mmcblkXp1
  • Otherwise, on your PC, format your MMC with Ext2 or Ext3/4 filesystems (booting on FAT is bad :-) ):
 $ sudo mkfs.ext2 /dev/sdX1   (replace X with your MMC reader drive letter, if your Laptop has an integrated
                                           MMC reader then use mmcblk0p1 instead of sdX1)
  • If not automatically detected/mounted by your distribution, mount your MMC/SD on your Host filesystem (for example in /media/mmc):
 $ sudo mkdir -p /media/mmc
 $ sudo mount /dev/sdX1 /media/mmc    (replace X with your MMC reader drive letter, if your Laptop has an integrated
                                                   MMC reader then use mmcblk0p1 instead of sdX1)

Put your rootfs and Linux kernel on the MMC/SD

  • Buildroot should be configured by default to generate a tar-ed rootfs, if not (no *.tar in buildroot/output/images/) then you can activate it with:
$ make menuconfig
Filesystem images  --->
...
    [*] tar the root filesystem
          Compression method (no compression)  --->
    ()    other random options to pass to tar
...
$ make
  • Then you have to uncompress the tar-ed rootfs to the MMC/SD card (mounted as /media/mmc on your PC in the following instructions).
Note Note: The APF51 (with U-Boot version older than 2013.04) and the APF9328 do not load the kernel from the SD card but use the one in Flash instead.
$ make shell_env
$ source armadeus_env.sh
$ sudo tar xvf $ARMADEUS_ROOTFS_TAR -C /media/mmc
  • You can also copy the Linux kernel to the rootfs /boot folder and dtb files for recent kernel supporting it:
$ sudo mkdir -p /media/mmc/boot/dtbs
$ sudo cp $ARMADEUS_BINARIES/$ARMADEUS_BOARD_NAME-linux.bin /media/mmc/boot/
$ sudo cp $ARMADEUS_BINARIES/*.dtb /media/mmc/boot/dtbs/
  • Then umount your MMC/SD from your PC:
$ sudo umount /media/mmc

Boot

  • Insert the MMC/SD/microSD in the corresponding slot of your Armadeus board and then under U-Boot do:
 BIOS> run mmcboot
  • if you want to automatically boot from SD at each startup, modify the bootcmd U-Boot macro:
 BIOS> setenv bootcmd run mmcboot
 BIOS> saveenv

(default bootcmd when you receive your board is run jffsboot = boot from FLASH)

Performances

Troubleshots

VFAT Code Page

If you encounter this message (or something similar):

Unable to load NLS charset cp437
FAT: codepage cp437 not found

you have to add the charset to the supported kernel ones:

$ make linux-menuconfig
File systems  ---> 
    -*- Native language support  --->
        <*>   Codepage 437 (United States, Canada)
        ...
        <*>   NLS ISO 8859-1  (Latin 1; Western European Languages)
        ...

U-Boot usage

SD cards can also be used with U-Boot. The following commands are useful:

  • Scan the MMC:
BIOS> mmc rescan
  • List the MMC content:
BIOS> fatls mmc 0
  • Load the file xxx.bin in RAM:
BIOS> fatload mmc 0 ${loadaddr} xxx.bin

Links