路径：/sys/kernel/debug/mmc0
[root@szclou mmc0]$ls
clock completed_events ios mmc0:0001 pending_events regs req state
[root@szclou mmc0]$cat ios
clock: 25000000 Hz
vdd: 21 (3.3 ~ 3.4 V)
bus mode: 2 (push-pull)
chip select: 0 (don't care)
power mode: 2 (on)
bus width: 0 (1 bits)
timing spec: 0 (legacy)
signal voltage: 0 (3.30 V)
特别注意，bus width 是1bit，所以eMMC读写速度比较慢，bus width可以配置为1bits、4bits、8bits。
[root@szclou mmc0]$cat clock
25000000
[root@szclou mmc0]$cat completed_events
0x00000001
[root@szclou mmc0]$cat mmc0\:0001/ext_csd
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
[root@szclou mmc0]$cat mmc0\:0001/
ext_csd state status
[root@szclou mmc0]$cat mmc0\:0001/state
0x00000005
[root@szclou mmc0]$cat mmc0\:0001/status
00000900
[root@szclou mmc0]$cat pending_events
0x00000000
[root@szclou mmc0]$cat regs
MR: 0x00001802 RDPROOF WRPROOF {CLKDIV,CLKODD}=4
DTOR: 0x0000007f
SDCR: 0x00000000
ARGR: 0x00010000
BLKR: 0x02000001 BCNT=1 BLKLEN=512
CSTOR: 0x00000000
SR: 0x0c000025 CMDRDY TXRDY NOTBUSY FIFOEMPTY XFRDONE
IMR: 0x00000000
DMA: 0x00000000 OFFSET=0 CHKSIZE=1
CFG: 0x00000000
[root@szclou mmc0]$cat req
[root@szclou mmc0]$cat state
0
