GPIO Driver

The JH7110 SoC platform integrates a pin controller that enables developers to configure the functions and properties of individual pins or pin groups. The Linux kernel pin control (pinctrl) driver can help developers with the following tasks:

  • Locate and name all the pins managed by the pin controller.
  • Implement pin multiplexing.
  • Provide options for pin configuration, including drive strength, power-up, power-down, and data attributes.
  • Interact with the GPIO subsystem.
  • Implement pin interrupt.

Block Diagram

The following figure displays the block diagram of the JH7100 GPIO pin control (pinctrl) driver module.

Figure 1. Block Diagram
The driver module includes the following layers:
Layer Description
Consumer The pin control interfaces and GPIO interfaces used by the device driver, such as SDIO and PCIe.
Interface The pin control and GPIO interfaces for users. See Interface Description for more information.
Pintrl Framework The original Linux system pin control framework. The framework enables developers to configure functions and properties of individual pins or pin groups
Driver The GPIO and pin control drivers of the JH7110 SoC platform.
Hardware The GPIO controller of the JH7110 SoC platform.

Pin Control Framework

The Pin control (Pinctrl) framework of the JH-7110 SoC platform consists of the following three components.
  • Pinctrl Core: The core layer of the pin control framework. The states–default, sleep, and idle–corresponds to the power management states of pin control.
  • Pinctrl Mux: Manages pin multiplexing functions.
  • Pinctrl Conf: Manages pin configuration settings.
The following figure illustrates the relationship among these components.
Figure 2. Pin Control Framework

Pin configurations may differ depending on the system operating mode. For example, the default pin configuration applies to normal mode, whereas the power-saving pin configuration applies to standby mode. Therefore, you can use the pin control framework to manage pin configurations according to the operating mode of the device.

Device Tree Source Code

The following code block shows the content of the GPIO device tree source code. 
        gpio: gpio@13040000 {
                compatible = "starfive,jh7110-sys-pinctrl";
                reg = <0x0 0x13040000 0x0 0x10000>;
                reg-names = "control";
                clocks = <&clkgen JH7110_SYS_IOMUX_PCLK>;
                resets = <&rstgen RSTN_U0_SYS_IOMUX_PRESETN>;
                interrupts = <86>;
                interrupt-controller;
                #gpio-cells = <2>;
                ngpios = <64>;
                status = "okay";
        };

        gpioa: gpio@17020000 {
                compatible = "starfive,jh7110-aon-pinctrl";
                reg = <0x0 0x17020000 0x0 0x10000>;
                reg-names = "control";
                resets = <&rstgen RSTN_U0_AON_IOMUX_PRESETN>;
                interrupts = <85>;
                interrupt-controller;
                #gpio-cells = <2>;
                ngpios = <4>;
                status = "okay";
        };
The following table describes the source code parameters:
Table 1. GPIO DT Parameters
Parameter Description
compatible Compatibility information, used to associate the driver and its target device.
reg Register base address "0x13040000" and range "0x10000".
reg-names Names of the registers used by the GPIO module.
clocks The clocks used by the GPIO module.
clock-names The names of the clocks used by the GPIO module.
resets The reset signals used by the GPIO module.
interrupts Hardware interrupt ID.
status

The work status of the GPIO module. To enable the module, set this bit to okay. To disable the module, set this bit to disabled.
Note: Make sure you do not change the bits of gpio-cells and ngpios.

Source Code Structure

The GPIO source code structure is listed as follows: 
linux
├── drivers
│   ├── pinctrl
│   │   ├── core.c
│   │   ├── core.h
│   │   ├── devicetree.c
│   │   ├── devicetree.h
│   │   ├── pinconf.c
│   │   ├── pinconf-generic.c
│   │   ├── pinconf.h
│   │   ├── pinmux.c
│   │   ├── pinmux.h
│   │   ├── starfive
│   │   │   ├── Kconfig
│   │   │   ├── Makefile
│   │   │   ├── pinctrl-starfive.c
│   │   │   ├── pinctrl-starfive.h
│   │   │   └── pinctrl-starfive-jh7110.c

├── include
│   ├── dt-bindings
│   │   ├── pinctrl
│   │   │   ├── starfive,jh7110-pinfunc.h
│   ├── linux
│   │   ├── pinctrl
│   │   │   ├── consumer.h
│   │   │   ├── devinfo.h
│   │   │   ├── machine.h
│   │   │   ├── pinconf-generic.h
│   │   │   ├── pinconf.h
│   │   │   ├── pinctrl.h
│   │   │   ├── pinctrl-state.h
│   │   │   └── pinmux.h