使用CAN1 RX引脚作为例子
arch\arm\boot\dts\imx6ul-14x14-evk.dts:
pinctrl_flexcan1: flexcan1grp{
fsl,pins = <
MX6UL_PAD_UART3_RTS_B__FLEXCAN1_RX 0x1b020
MX6UL_PAD_UART3_CTS_B__FLEXCAN1_TX 0x1b020
>;
};
而imx6ul-14x14-evk.dts包含imx6ul.dtsi(#include "imx6ul.dtsi")，而imx6ul.dtsi又包含imx6ul-pinfunc.h
arch\arm\boot\dts\imx6ul-pinfunc.h中对FLEXCAN1_RX有如下定义：
/*
* The pin function ID is a tuple of
* <mux_reg conf_reg input_reg mux_mode input_val>
*/
#define MX6UL_PAD_UART3_RTS_B__FLEXCAN1_RX 0x00B0 0x033C 0x0584 0x2 0x0
mux_reg: IOMUXC_SW_MUX_CTL_PAD_UART3_RTS_B: 偏移地址00B0
conf_reg: IOMUXC_SW_PAD_CTL_PAD_UART3_RTS_B: 偏移地址033C
input_reg: IOMUXC_FLEXCAN1_RX_SELECT_INPUT: 偏移地址0584
mux_reg: IOMUXC_SW_MUX_CTL_PAD_UART3_RTS_B[3:0]: 0x2 - 配置成ALT2(FLEXCAN1_RX)
input_reg: IOMUXC_FLEXCAN1_RX_SELECT_INPUT: 0x0 - 复用PAD_UART3_RTS_B(由PAD_UART3_RTS_B配置而来)
对于imx6ul-14x14-evk.dts中的MX6UL_PAD_UART3_RTS_B__FLEXCAN1_RX 0x1b020主要是对IOMUXC_SW_PAD_CTL_PAD_UART3_RTS_B进行设置。
即：
conf_reg: IOMUXC_SW_PAD_CTL_PAD_UART3_RTS_B的值为: 0x1b020