因内核驱动限制，310b的spi总线速率可配置如下：

max_speed_hz:100000 is valid
max_speed_hz:120000 is valid
max_speed_hz:125000 is valid
max_speed_hz:150000 is valid
max_speed_hz:156250 is valid
max_speed_hz:187500 is valid
max_speed_hz:200000 is valid
max_speed_hz:234375 is valid
max_speed_hz:250000 is valid
max_speed_hz:300000 is valid
max_speed_hz:312500 is valid
max_speed_hz:375000 is valid
max_speed_hz:390625 is valid
max_speed_hz:468750 is valid
max_speed_hz:500000 is valid
max_speed_hz:600000 is valid
max_speed_hz:625000 is valid
max_speed_hz:750000 is valid
max_speed_hz:781250 is valid
max_speed_hz:937500 is valid
max_speed_hz:1000000 is valid
max_speed_hz:1171875 is valid
max_speed_hz:1250000 is valid
max_speed_hz:1500000 is valid
max_speed_hz:1562500 is valid
max_speed_hz:1875000 is valid
max_speed_hz:2343750 is valid
max_speed_hz:2500000 is valid
max_speed_hz:3000000 is valid
max_speed_hz:3125000 is valid
max_speed_hz:3750000 is valid
max_speed_hz:4687500 is valid
max_speed_hz:5000000 is valid
max_speed_hz:6250000 is valid
max_speed_hz:7500000 is valid
max_speed_hz:9375000 is valid
max_speed_hz:12500000 is valid
max_speed_hz:15000000 is valid
max_speed_hz:18750000 is valid
max_speed_hz:24000000 is valid

其他速率配置进去后会失败，无法访问spi外设。切记