Introduction

Architecture

The I2C driver follows Linux framework: i2c-core-base.c, i2c-core-of.c, i2c-dev.c, i2c-boardinfo.c. The I2C software architecture is illustrated below.

Refer to I2C for more details of I2C framework.

Implementation

The I2C driver is implemented as following files:

File	Description
`<linux>/drivers/rtkdrivers/i2c/Kconfig`	I2C driver Kconfig
`<linux>/drivers/rtkdrivers/i2c/Makefile`	I2C driver Makefile
`<linux>/drivers/rtkdrivers/i2c/rtk-i2c-core.c`	I2C core functions.
`<linux>/drivers/rtkdrivers/i2c/rtk-i2c-master.c`	I2C master functions.
`<linux>/drivers/rtkdrivers/i2c/rtk-i2c-slave.c`	I2C slave functions.
`<linux>/drivers/rtkdrivers/i2c/i2c-realtek.h`	I2C related function declaration, macro definition, structure definition and the other header files quoted.

Configuration

DTS Configuration

I2C DTS:

i2c0: i2c0@4200F000 {
   compatible = "realtek,ameba-i2c";
   reg = <0x4200F000 0x100>;
   interrupts = <GIC_SPI 22 IRQ_TYPE_LEVEL_HIGH>;
   clocks = <&rcc RTK_CKE_I2C0>;
   rtk,i2c-index = <0>;
   rtk,use-poll-type = <0>;
   rtk,i2c-clk = <100000>;
   rtk,wait-timeout = <0x1000>;
   rtk,i2c-reg-slave-num = <0>;
   status = "disabled";
};

Property Description

Property	Description	Configurable?
compatible	The description of I2C driver: “realtek,ameba-i2c”.	No
reg	The hardware address and size for I2C device: <0x4200F000 0x100>.	No
interrupts	The GIC number of I2C device: <GIC_SPI 22 IRQ_TYPE_LEVEL_HIGH>.	No
clocks	The clock of I2C device: <&rcc RTK_CKE_I2C0>.	No
rtk,use-poll-type	0: interrupt mode (default) 1: poll mode	0/1
rtk,i2c-clk	Specifies the I2C Bus Clock (in Hz).	1~400000
rtk,wait-timeout	Setting 0x1000 means that I2C master will wait transfer for 4096ms, and then timeout.	Yes
rtk,i2c-reg-slave-num	Register slaves on I2C bus. 0: I2C master 1/2: I2C slave numbers	0/1/2
status	Whether enable this device. “disabled” “okay”	Yes

Pinmux

I2C device	Port name	Pin name	pinctrl description
I2C0	PA0	SDA	<&i2c0_pins>
I2C0	PA1	SCL	<&i2c0_pins>
I2C0	PA5	SDA	Shall revise pins in i2c0_pins
I2C0	PA6	SCL	Shall revise pins in i2c0_pins
I2C0	PA9	SDA	Shall revise pins in i2c0_pins
I2C0	PA10	SCL	Shall revise pins in i2c0_pins
I2C0	PA30	SDA	Shall revise pins in i2c0_pins
I2C0	PA31	SCL	Shall revise pins in i2c0_pins
I2C0	PB5	SDA	Shall revise pins in i2c0_pins
I2C0	PB6	SCL	Shall revise pins in i2c0_pins
I2C0	PB29	SDA	Shall revise pins in i2c0_pins
I2C0	PB30	SCL	Shall revise pins in i2c0_pins
I2C1	PA3	SDA	Shall revise pins in i2c1_pins
I2C1	PA4	SCL	Shall revise pins in i2c1_pins
I2C1	PA13	SDA	Shall revise pins in i2c1_pins
I2C1	PA14	SCL	Shall revise pins in i2c1_pins
I2C1	PA20	SDA	Shall revise pins in i2c1_pins
I2C1	PA21	SCL	Shall revise pins in i2c1_pins
I2C1	PA24	SDA	Shall revise pins in i2c1_pins
I2C1	PA25	SCL	Shall revise pins in i2c1_pins
I2C1	PB12	SDA	<&i2c1_pins>
I2C1	PB13	SCL	<&i2c1_pins>
I2C1	PB25	SDA	Shall revise pins in i2c1_pins
I2C1	PB26	SCL	Shall revise pins in i2c1_pins
I2C2	PA7	SDA	Shall revise pins in i2c2_pins
I2C2	PA8	SCL	Shall revise pins in i2c2_pins
I2C2	PA11	SDA	Shall revise pins in i2c2_pins
I2C2	PA12	SCL	Shall revise pins in i2c2_pins
I2C2	PA15	SDA	Shall revise pins in i2c2_pins
I2C2	PA16	SCL	Shall revise pins in i2c2_pins
I2C2	PA28	SDA	Shall revise pins in i2c2_pins
I2C2	PA29	SCL	Shall revise pins in i2c2_pins
I2C2	PB4	SDA	Shall revise pins in i2c2_pins
I2C2	PB3	SCL	Shall revise pins in i2c2_pins
I2C2	PB10	SDA	<&i2c2_pins>
I2C2	PB11	SCL	<&i2c2_pins>

Note

The pinmux can be revised according to specific conditions in <dts>/rtl8730e-pinctrl.dtsi.

Refer to pinctrl application note for more details.

I2C Group

The I2C group has three I2C devices named I2C0, I2C1 and I2C2. The usage of I2C devices are the same.

aliases {
   i2c0 = "/ocp/i2c0@0x4200F000";
   i2c1 = "/ocp/i2c1@0x400EF000";
   i2c2 = "/ocp/i2c2@0x400F0000";
};

Build Configuration

Select Drivers for Realtek > I2C controller driver. If I2C slave mode is expected, enter I2C controller driver and enable I2C slave driver.

APIs

APIs for User Space

Master Mode

The I2C master interfaces for user space are provided by <linux>/drivers/i2c/dev.c. Here are some commonly used APIs to control I2C device.

Interfaces	Introduction
i2cdev_open	Open an I2C device.
i2cdev_release	Release an I2C device.
i2cdev_ioctl	Configure I2C parameters, control read/write I2C data.
i2cdev_write	Call I2C driver to send a message.
i2cdev_read	Call I2C driver to read a message.

Note

For more details, refer to the official document in I2C Device Interface

The I2C master demo for user space is located at <test>/i2c.

Slave Mode

None.

APIs for Kernel Space

Master Mode

The I2C master interfaces for kernel space are provided by <linux>/drivers/i2c/i2c-core-base.c. Here are some commonly used API to control I2C master device.

Interfaces

Introduction

module_i2c_driver

Register an I2C client module.

i2c_transfer

Call I2C driver to send a message or read a message.

msg->flags & I2C_M_RD = 1 // read

msg->flags & I2C_M_RD = 0 // write

Note

For more details, refer to Writing I2C Clients

Slave Mode

The I2C slave interfaces for kernel space are provided by <linux>/drivers/i2c/i2c-core-slave.c. Here are some commonly used API to control I2C slave device.

Interfaces	Introduction
i2c_slave_register	Register an I2C slave device.
i2c_slave_unregister	Unregister an I2C slave device.

Note

For more details, refer to I2C slave interface

The I2C slave demo is located at <test>/i2c-slave. Pay attention to modify the rtk, i2c-reg-slave-num parameter in Property Description to configure an I2C core for the slave.