Set emmc to HS400 use 200MHz

I want to set emmc HS400, and clock 200MHz, I set the f_max and max-frequency to 200000000 at kvim_linux.dts, it can let emmc to HS400 and clock 200MHz, but the actual clock just 166666666 Hz, Who can help me set the actual clock up to 200MHz?

soot@Khadas:/sys/kernel/debug/emmc/emmc:0001# cat cat /sys/kernel/debug/emmc/io
cat: cat: No such file or directory
clock: 200000000 Hz
actual clock: 166666666 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: 3 (8 bits)
timing spec: 10 (mmc HS400)
signal voltage: 1 (1.80 V)
driver type: 0 (driver type B)