相关用法在之前的[Sipeed 内部培训] V831/V833 的 SDK 的 kernel & package 的开发方法 的『关于适配和测试常见的基础外设驱动，从上层用户空间的软件到底层硬件寄存器之间的联系。』 一节可知，最近可以给新人参考说明用。
设备树引脚的分配
spi1_pins_a: spi1@0 {
allwinner,pins = "PH0", "PH1", "PH2";
allwinner,pname = "spi1_sclk", "spi1_mosi",
"spi1_miso";
allwinner,function = "spi1";
allwinner,muxsel = <4>;
allwinner,drive = <1>;
allwinner,pull = <0>;
};
同学们可能知道基本的信息，其中 function muxsel 是什么意思呢？
首先通过 pinmux-pins 打印出来
root@sipeed:/# cat /sys/kernel/debug/pinctrl/pio/pinmux-pins
Pinmux settings per pin
Format: pin (name): mux_owner gpio_owner hog?
pin 64 (PC0): sdc2 (GPIO UNCLAIMED) function sdc2 group PC0
pin 65 (PC1): sdc2 (GPIO UNCLAIMED) function sdc2 group PC1
pin 66 (PC2): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 67 (PC3): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 68 (PC4): sdc2 (GPIO UNCLAIMED) function sdc2 group PC4
pin 69 (PC5): sdc2 (GPIO UNCLAIMED) function sdc2 group PC5
pin 70 (PC6): sdc2 (GPIO UNCLAIMED) function sdc2 group PC6
pin 71 (PC7): sdc2 (GPIO UNCLAIMED) function sdc2 group PC7
pin 72 (PC8): sdc2 (GPIO UNCLAIMED) function sdc2 group PC8
pin 73 (PC9): sdc2 (GPIO UNCLAIMED) function sdc2 group PC9
pin 74 (PC10): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 75 (PC11): sdc2 (GPIO UNCLAIMED) function sdc2 group PC11
pin 96 (PD0): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 97 (PD1): 5020000.eth (GPIO UNCLAIMED) function gmac0 group PD1
pin 98 (PD2): 5020000.eth (GPIO UNCLAIMED) function gmac0 group PD2
pin 99 (PD3): 5020000.eth (GPIO UNCLAIMED) function gmac0 group PD3
pin 100 (PD4): 5020000.eth (GPIO UNCLAIMED) function gmac0 group PD4
pin 101 (PD5): 5020000.eth (GPIO UNCLAIMED) function gmac0 group PD5
pin 102 (PD6): 5020000.eth (GPIO UNCLAIMED) function gmac0 group PD6
pin 103 (PD7): 5020000.eth (GPIO UNCLAIMED) function gmac0 group PD7
pin 104 (PD8): 5020000.eth (GPIO UNCLAIMED) function gmac0 group PD8
pin 105 (PD9): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 106 (PD10): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 107 (PD11): (MUX UNCLAIMED) pio:107
pin 108 (PD12): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 109 (PD13): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 110 (PD14): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 111 (PD15): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 112 (PD16): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 113 (PD17): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 114 (PD18): 5020000.eth (GPIO UNCLAIMED) function ephy group PD18
pin 115 (PD19): (MUX UNCLAIMED) pio:115
pin 116 (PD20): 5020000.eth (GPIO UNCLAIMED) function gmac0 group PD20
pin 117 (PD21): 5020000.eth (GPIO UNCLAIMED) function gmac0 group PD21
pin 118 (PD22): (MUX UNCLAIMED) pio:118
pin 128 (PE0): csi1 (GPIO UNCLAIMED) function csi1 group PE0
pin 129 (PE1): sensor1 (GPIO UNCLAIMED) function csi_mclk1 group PE1
pin 130 (PE2): csi1 (GPIO UNCLAIMED) function csi1 group PE2
pin 131 (PE3): csi1 (GPIO UNCLAIMED) function csi1 group PE3
pin 132 (PE4): csi1 (GPIO UNCLAIMED) function csi1 group PE4
pin 133 (PE5): csi1 (GPIO UNCLAIMED) function csi1 group PE5
pin 134 (PE6): csi1 (GPIO UNCLAIMED) function csi1 group PE6
pin 135 (PE7): csi1 (GPIO UNCLAIMED) function csi1 group PE7
pin 136 (PE8): csi1 (GPIO UNCLAIMED) function csi1 group PE8
pin 137 (PE9): csi1 (GPIO UNCLAIMED) function csi1 group PE9
pin 138 (PE10): csi1 (GPIO UNCLAIMED) function csi1 group PE10
pin 139 (PE11): csi1 (GPIO UNCLAIMED) function csi1 group PE11
pin 140 (PE12): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 141 (PE13): (MUX UNCLAIMED) pio:141
pin 142 (PE14): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 143 (PE15): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 144 (PE16): twi4 (GPIO UNCLAIMED) function twi0 group PE16
pin 145 (PE17): twi4 (GPIO UNCLAIMED) function twi1 group PE17
pin 146 (PE18): uart2 (GPIO UNCLAIMED) function uart2 group PE18
pin 147 (PE19): uart2 (GPIO UNCLAIMED) function uart2 group PE19
pin 148 (PE20): (MUX UNCLAIMED) pio:148
pin 149 (PE21): (MUX UNCLAIMED) pio:149
pin 160 (PF0): sdc0 (GPIO UNCLAIMED) function sdc0 group PF0
pin 161 (PF1): sdc0 (GPIO UNCLAIMED) function sdc0 group PF1
pin 162 (PF2): sdc0 (GPIO UNCLAIMED) function sdc0 group PF2
pin 163 (PF3): sdc0 (GPIO UNCLAIMED) function sdc0 group PF3
pin 164 (PF4): sdc0 (GPIO UNCLAIMED) function sdc0 group PF4
pin 165 (PF5): sdc0 (GPIO UNCLAIMED) function sdc0 group PF5
pin 166 (PF6): (MUX UNCLAIMED) pio:166
pin 192 (PG0): sdc1 (GPIO UNCLAIMED) function io_disabled group PG0
pin 193 (PG1): sdc1 (GPIO UNCLAIMED) function io_disabled group PG1
pin 194 (PG2): sdc1 (GPIO UNCLAIMED) function io_disabled group PG2
pin 195 (PG3): sdc1 (GPIO UNCLAIMED) function io_disabled group PG3
pin 196 (PG4): sdc1 (GPIO UNCLAIMED) function io_disabled group PG4
pin 197 (PG5): sdc1 (GPIO UNCLAIMED) function io_disabled group PG5
pin 198 (PG6): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 199 (PG7): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 224 (PH0): spi1 (GPIO UNCLAIMED) function spi1 group PH0
pin 225 (PH1): spi1 (GPIO UNCLAIMED) function spi1 group PH1
pin 226 (PH2): spi1 (GPIO UNCLAIMED) function spi1 group PH2
pin 227 (PH3): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 228 (PH4): spi1 (GPIO UNCLAIMED) function spi1 group PH4
pin 229 (PH5): twi2 (GPIO UNCLAIMED) function twi2 group PH5
pin 230 (PH6): twi2 (GPIO UNCLAIMED) function twi2 group PH6
pin 231 (PH7): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 232 (PH8): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 233 (PH9): uart0 (GPIO UNCLAIMED) function uart0 group PH9
pin 234 (PH10): uart0 (GPIO UNCLAIMED) function uart0 group PH10
pin 235 (PH11): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 236 (PH12): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 237 (PH13): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 238 (PH14): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 239 (PH15): (MUX UNCLAIMED) (GPIO UNCLAIMED)
pin 256 (PI0): sensor0 (GPIO UNCLAIMED) function csi_mclk0 group PI0
pin 257 (PI1): twi1 (GPIO UNCLAIMED) function twi1 group PI1
pin 258 (PI2): twi1 (GPIO UNCLAIMED) function twi1 group PI2
pin 259 (PI3): (MUX UNCLAIMED) pio:259
pin 260 (PI4): (MUX UNCLAIMED) pio:260
可知 function 就是 function spi1 表示定义的引脚功能范围和用途，接着是 allwinner,muxsel = <4>; 为什么是 4 ？
看手册可知。
如果配置成 2 则打印寄存器的时候会发现配置成 pwm 而非 spi ，这时候就会出现，有了能操作的设备，但实际功能不生效。