i.mx6ul引脚复用

使用CAN1 RX引脚作为例子

arch\arm\boot\dts\imx6ul-14x14-evk.dts:

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1. pinctrl_flexcan1: flexcan1grp{  
2.     fsl,pins = <  
3.         MX6UL_PAD_UART3_RTS_B__FLEXCAN1_RX  0x1b020  
4.         MX6UL_PAD_UART3_CTS_B__FLEXCAN1_TX  0x1b020  
5.     >;  
6. };  

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