mmc command

Synopsis

mmc info
mmc read addr blk# cnt
mmc write addr blk# cnt
mmc erase blk# cnt
mmc rescan [mode]
mmc part
mmc dev [dev] [part] [mode]
mmc list
mmc wp
mmc bootbus <dev> <boot_bus_width> <reset_boot_bus_width> <boot_mode>
mmc bootpart-resize <dev> <dev part size MB> <RPMB part size MB>
mmc partconf <dev> [[varname] | [<boot_ack> <boot_partition> <partition_access>]]
mmc rst-function <dev> <value>
mmc reg read <reg> <offset> [env]

Description

The mmc command is used to control MMC(eMMC/SD) device.

The ‘mmc info’ command displays information (Manufacturer ID, OEM, Name, Bus Speed, Mode, …) of MMC device.

The ‘mmc read’ command reads raw data to memory address from MMC device with block offset and count.

The ‘mmc write’ command writes raw data to MMC device from memory address with block offset and count.

addr
memory address

blk#
start block offset

cnt
block count

The ‘mmc erase’ command erases cnt blocks on the MMC device starting at block blk#.

blk#
start block offset

cnt
block count

The ‘mmc rescan’ command scans the available MMC device.

mode
speed mode to set. CONFIG_MMC_SPEED_MODE_SET should be enabled. The requested speed mode is passed as a decimal number according to the following table:

Speed mode

Description

0

MMC legacy

1

MMC High Speed (26MHz)

2

SD High Speed (50MHz)

3

MMC High Speed (52MHz)

4

MMC DDR52 (52MHz)

5

UHS SDR12 (25MHz)

6

UHS SDR25 (50MHz)

7

UHS SDR50 (100MHz)

8

UHS DDR50 (50MHz)

9

UHS SDR104 (208MHz)

10

HS200 (200MHz)

11

HS400 (200MHz)

12

HS400ES (200MHz)

A speed mode can be set only if it has already been enabled in the device tree

The ‘mmc part’ command displays the list available partition on current mmc device.

The ‘mmc dev’ command shows or set current mmc device.

dev
device number to change

part
partition number to change

mode
speed mode to set. CONFIG_MMC_SPEED_MODE_SET should be enabled. The requested speed mode is passed as a decimal number according to the following table:

Speed mode

Description

0

MMC legacy

1

MMC High Speed (26MHz)

2

SD High Speed (50MHz)

3

MMC High Speed (52MHz)

4

MMC DDR52 (52MHz)

5

UHS SDR12 (25MHz)

6

UHS SDR25 (50MHz)

7

UHS SDR50 (100MHz)

8

UHS DDR50 (50MHz)

9

UHS SDR104 (208MHz)

10

HS200 (200MHz)

11

HS400 (200MHz)

12

HS400ES (200MHz)

A speed mode can be set only if it has already been enabled in the device tree

The ‘mmc list’ command displays the list available devices.

The ‘mmc wp’ command enables “power on write protect” function for boot partitions.

The ‘mmc bootbus’ command sets the BOOT_BUS_WIDTH field. (Refer to eMMC specification)

boot_bus_width

0x0
x1 (sdr) or x4(ddr) buswidth in boot operation mode (default)

0x1
x4 (sdr/ddr) buswidth in boot operation mode

0x2
x8 (sdr/ddr) buswidth in boot operation mode

0x3
Reserved

reset_boot_bus_width

0x0
Reset buswidth to x1, Single data reate and backward compatible timing after boot operation (default)

0x1
Retain BOOT_BUS_WIDTH and BOOT_MODE value after boot operation. This is relevant to Push-pull mode operation only

boot_mode

0x0
Use single data rate + backward compatible timing in boot operation (default)

0x1
Use single data rate + High Speed timing in boot operation mode

0x2
Use dual data rate in boot operation

0x3
Reserved

The ‘mmc partconf’ command shows or changes PARTITION_CONFIG field.

varname
When showing the PARTITION_CONFIG, an optional environment variable to store the current boot_partition value into.

boot_ack
boot acknowledge value

boot_partition

boot partition to enable for boot

0x0
Device not boot enabled(default)

0x1
Boot partition1 enabled for boot

0x2
Boot partition2 enabled for boot

0x7
User area enabled for boot

others
Reserved

partition_access
partitions to access

The ‘mmc bootpart-resize’ command changes sizes of boot and RPMB partitions.

dev
device number

boot part size MB
target size of boot partition

RPMB part size MB
target size of RPMB partition

The ‘mmc rst-function’ command changes the RST_n_FUNCTION field. WARNING : This is a write-once field. (Refer to eMMC specification)

value

0x0
RST_n signal is temporarily disabled (default)

0x1
RST_n signal is permanently enabled

0x2
RST_n signal is permanently disabled

0x3
Reserved

The ‘mmc reg read <reg> <offset> [env]’ reads eMMC card register and either print it to standard output, or store the value in environment variable.

<reg> with optional offset <offset> into the register array, and print it to standard output or store it into environment variable [env].

reg

cid
The Device IDentification (CID) register. Uses offset.

csd
The Device-Specific Data (CSD) register. Uses offset.

dsr
The driver stage register (DSR).

ocr
The operation conditions register (OCR).

rca
The relative Device address (RCA) register.

extcsd
The Extended CSD register. Uses offset.

offset
For ‘cid’/’csd’ 128 bit registers ‘[0..3]’ in 32-bit increments. For ‘extcsd’ 512 bit register ‘[0..512,all]’ in 8-bit increments, or ‘all’ to read the entire register.

env
Optional environment variable into which 32-bit value read from register should be stored.

Examples

The ‘mmc info’ command displays device’s capabilities:

=> mmc info
Device: EXYNOS DWMMC
Manufacturer ID: 45
OEM: 100
Name: SDW16
Bus Speed: 52000000
Mode: MMC DDR52 (52MHz)
Rd Block Len: 512
MMC version 5.0
High Capacity: Yes
Capacity: 14.7 GiB
Bus Width: 8-bit DDR
Erase Group Size: 512 KiB
HC WP Group Size: 8 MiB
User Capacity: 14.7 GiB WRREL
Boot Capacity: 4 MiB ENH
RPMB Capacity: 4 MiB ENH
Boot area 0 is not write protected
Boot area 1 is not write protected

The raw data can be read/written via ‘mmc read/write’ command:

=> mmc read 40000000 5000 100
MMC read: dev # 0, block # 20480, count 256 ... 256 blocks read: OK

=> mmc write 40000000 5000 100
MMC write: dev # 0, block # 20480, count 256 ... 256 blocks written: OK

The partition list can be shown via ‘mmc part’ command:

=> mmc part
Partition Map for MMC device 0  --   Partition Type: DOS

Part    Start Sector    Num Sectors     UUID            Type
   8192            131072          dff8751a-01     0e Boot
   139264          6291456         dff8751a-02     83
   6430720         1048576         dff8751a-03     83
   7479296         23298048        dff8751a-04     05 Extd
   7481344         307200          dff8751a-05     83
   7790592         65536           dff8751a-06     83
   7858176         16384           dff8751a-07     83
   7876608         22900736        dff8751a-08     83

The current device can be shown or set via ‘mmc dev’ command:

=> mmc dev
switch to partitions #0, OK
mmc0(part0) is current device
=> mmc dev 2 0
switch to partitions #0, OK
mmc2 is current device
=> mmc dev 0 1 4
switch to partitions #1, OK
mmc0(part 1) is current device

The list of available devices can be shown via ‘mmc list’ command:

=> mmc list
mmc list
EXYNOS DWMMC: 0 (eMMC)
EXYNOS DWMMC: 2 (SD)

Configuration

The mmc command is only available if CONFIG_CMD_MMC=y. Some commands need to enable more configuration.

write, erase: CONFIG_MMC_WRITE
bootbus, bootpart-resize, partconf, rst-function: CONFIG_SUPPORT_EMMC_BOOT=y