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>

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 required speed mode is passed as the index from the following list.

0 - MMC_LEGACY 1 - MMC_HS 2 - SD_HS 3 - MMC_HS_52 4 - MMC_DDR_52 5 - UHS_SDR12 6 - UHS_SDR25 7 - UHS_SDR50 8 - UHS_DDR50 9 - UHS_SDR104 10 - MMC_HS_200 11 - MMC_HS_400 12 - MMC_HS_400_ES

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

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 0x40000000 0x5000 0x100
MMC read: dev # 0, block # 20480, count 256 ... 256 blocks read: OK

=> mmc write 0x40000000 0x5000 0x10
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
  1     8192            131072          dff8751a-01     0e Boot
  2     139264          6291456         dff8751a-02     83
  3     6430720         1048576         dff8751a-03     83
  4     7479296         23298048        dff8751a-04     05 Extd
  5     7481344         307200          dff8751a-05     83
  6     7790592         65536           dff8751a-06     83
  7     7858176         16384           dff8751a-07     83
  8     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