为R329添加i2c设备

添加设备树

设备树在/linux/arch/arm64/boot/dts/allwinner/路径下，和r329相关的设备树有

sun50i-r329-maix-iia.dtsi
sun50i-r329-maixsense.dts
sun50i-r329.dtsi

三个，其中没有i2c的定义。

参考下隔壁H6的设备树：

引脚定义：

			i2c0_pins: i2c0-pins {
				pins = "PD25", "PD26";
				function = "i2c0";
			};

I2C描述：

		i2c0: i2c@5002000 {
			compatible = "allwinner,sun50i-h6-i2c",
				     "allwinner,sun6i-a31-i2c";
			reg = <0x05002000 0x400>;
			interrupts = <GIC_SPI 4 IRQ_TYPE_LEVEL_HIGH>;
			clocks = <&ccu CLK_BUS_I2C0>;
			resets = <&ccu RST_BUS_I2C0>;
			pinctrl-names = "default";
			pinctrl-0 = <&i2c0_pins>;
			status = "disabled";
			#address-cells = <1>;
			#size-cells = <0>;
		};

注册引脚

原理图如下：

在pinctrl中，可以看到PH8 PH9是i2c1：

	SUNXI_PIN(SUNXI_PINCTRL_PIN(H, 8),
		  SUNXI_FUNCTION(0x0, "gpio_in"),
		  SUNXI_FUNCTION(0x1, "gpio_out"),
		  SUNXI_FUNCTION(0x2, "i2c1"),		/* SDA */
		  SUNXI_FUNCTION(0x3, "spi1"),		/* WP/DBI-TE */
		  SUNXI_FUNCTION(0x4, "ledc"),		/* DO */
		  SUNXI_FUNCTION(0x5, "ir"),		/* TX */
		  SUNXI_FUNCTION_IRQ_BANK(0x6, 3, 8)),	/* PH_EINT8 */
	SUNXI_PIN(SUNXI_PINCTRL_PIN(H, 9),
		  SUNXI_FUNCTION(0x0, "gpio_in"),
		  SUNXI_FUNCTION(0x1, "gpio_out"),
		  SUNXI_FUNCTION(0x2, "i2c1"),		/* SCK */
		  SUNXI_FUNCTION(0x3, "spi1"),		/* HOLD/DBI-DCX/DBI-WRX */
		  SUNXI_FUNCTION(0x4, "spdif"),		/* IN */
		  SUNXI_FUNCTION(0x5, "ir"),		/* RX */
		  SUNXI_FUNCTION_IRQ_BANK(0x6, 3, 9)),	/* PH_EINT9 */

在pio: pinctrl@2000400添加引脚定义：

			i2c1_ph_pins: i2c1-ph-pins {
				pins = "PH8", "PH9";
				function = "i2c1";
			};

添加i2c描述

查找i2c寄存器地址

在USER manual中

7.1.5 Register List

Module Name	BaseAddress
TWI0	0x02502000
TWI1	0x02502400
R_TWI0	0x07081400

这里使用的是TWI1，因此地址是0x02502400，地址范围0x400；

查找compatible

在 linux/drivers/i2c/busses/没有相关描述，抄一个隔壁的

查找中断号

Interrupt Number	Interrupt Source
41	TWI0
42	TWI1

参考标准串口使用的GIC_SPI(SPI：shared processor interrupts 中断号 32 ～32+224),
得到r_uart的中断号42-32=10

查找时钟及复位号

在#include <dt-bindings/clock/sun50i-r329-ccu.h> 和#include <dt-bindings/reset/sun50i-r329-ccu.h>中

#define RST_BUS_I2C1		18

#define CLK_BUS_I2C1		37

整体描述如下：

		i2c1: i2c@2502400{
			compatible = "allwinner,sun6i-a31-i2c";
			reg = <0x02502400 0x400>;
			interrupts = <GIC_SPI 10 IRQ_TYPE_LEVEL_HIGH>;
			clocks = <&ccu CLK_BUS_I2C1>;
			resets = <&ccu RST_BUS_I2C1>;
			pinctrl-names = "default";
			pinctrl-0 = <&i2c1_ph_pins>;
			status = "disabled";
		};

添加到dtbs文件中。

启用I2C设备

在sun50i-r329-maixsense.dts中开启i2c1

&i2c1{
	status = "okay";
};

声明i2c1设备名

	aliases {
		serial0 = &uart0;
		serial1 = &r_uart;
		mmc0 = &mmc0;
		i2c1 = &i2c1;
	};

编译，然后将设备树文件放入maixsense中。

测试

启动后，可以列出i2c设备：

maixsense:~:# ls /sys/bus/i2c/devices 
i2c-1
maixsense:~:# ls /dev/i2c* 
/dev/i2c-1

完整设备树文件见linux/arch/arm64/boot/dts/allwinner at r329-wip · USTHzhanglu/linux (github.com)