mmc接口（4）——mmc基础操作

横山郡守

已于 2022-01-26 18:08:04 修改

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分类专栏： Linux 通用接口文章标签： emmc linux u-boot

于 2021-12-21 16:29:54 首次发布

本文链接：https://blog.youkuaiyun.com/scottmvp/article/details/122065411

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本文详细介绍了U-Boot环境下MMCCmd命令的使用方法，包括mmcinfo、mmcread、mmcwrite等子命令的具体用法，并通过实例展示了如何读取和擦除EMMC设备上的环境变量。

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uboot 指令

mmc指令

=> mmc -help
mmc - MMC sub system

Usage:
mmc info - display info of the current MMC device
mmc read addr blk# cnt
mmc write addr blk# cnt
mmc erase blk# cnt
mmc rescan
mmc part - lists available partition on current mmc device
mmc dev [dev] [part] - show or set current mmc device [partition]
mmc list - lists available devices
mmc hwpartition [args...] - does hardware partitioning
  arguments (sizes in 512-byte blocks):
    [user [enh start cnt] [wrrel {on|off}]] - sets user data area attributes
    [gp1|gp2|gp3|gp4 cnt [enh] [wrrel {on|off}]] - general purpose partition
    [check|set|complete] - mode, complete set partitioning completed
  WARNING: Partitioning is a write-once setting once it is set to complete.
  Power cycling is required to initialize partitions after set to complete.
mmc setdsr <value> - set DSR register value

md指令

=> md.b      
md - memory display

Usage:
md [.b, .w, .l] address [# of objects]

应用示例

s5p4418# mmc list
NXP DWMMC: 0		//sd卡
 NXP DWMMC: 1
 NXP DWMMC: 2		//emmc

s5p4418# mmc info
Device: NXP DWMMC
Manufacturer ID: 15
OEM: 100
Name: 8GME4
Tran Speed: 52000000
Rd Block Len: 512
MMC version 4.0
High Capacity: Yes
Capacity: 7.3 GiB
Bus Width: 4-bit

emmc的第0x400块开始的2块存放着环境变量
读取环境变量

mmc read 48000000 400 2
md.b 48000000 3b0
md.b 48031400 3b0

480313f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
48031400: 5d d0 a6 e0 62 61 75 64 72 61 74 65 3d 31 31 35    ]...baudrate=115
......
48031790: 6f 75 74 3d 73 65 72 69 61 6c 00 74 70 3d 63 61    out=serial.tp=ca
480317a0: 70 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    p...............
480317b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................

擦除emmc存放环境变量的两块