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GPIO Configuration

1. Hardware confirmation​

Before editing, record the controller index, pinmux, voltage domain, supplies, reset/enable signals, interrupt, and external device model. For high-speed interfaces, also confirm topology, reference clock, and PHY sharing.

2. Locate the active platform configuration​

cd <ANDROID_TOP>/longan
find bsp device kernel -type f \( -name '*.dts' -o -name '*.dtsi' -o -name 'Kconfig' \)   | grep -Ei '<MODULE>|t527|sun55iw3'
grep -Rni '<compatible-or-config-keyword>' bsp device kernel

Do not assume that paths in a release guide exactly match the active branch, especially when moving from an older kernel to the Linux 5.15 independent BSP repository.

3. Kernel menuconfig​

./build.sh menuconfig

Check the following items:

  • CONFIG_PINCTRL
  • CONFIG_GPIOLIB
  • CONFIG_DEBUG_FS
  • CONFIG_AW_PINCTRL_DEBUGFS
  • CONFIG_GPIO_SYSFS (only required for legacy sysfs debugging)

Save the configuration:

./build.sh saveconfig
# Verify which target defconfig changed
git diff -- device bsp

4. Device Tree example​

The following is a reference structure. Do not duplicate or override SoC-level reg, interrupts, clocks, or resets unless an erratum or an official patch requires it.

&pio {
        /* Each item corresponds to an interrupt-capable GPIO bank，The specific quantity is based on SoC dtsi Subject to */
        input-debounce = <0 0 0 0 1 0 0 0 0>;
};

example_pins: example-pins {
        pins = "PI14";
        function = "gpio_out";
        drive-strength = <20>;
        bias-pull-up;
};

example_device {
        compatible = "vendor,example-device";
        enable-gpios = <&pio PI 14 GPIO_ACTIVE_HIGH>;
        pinctrl-names = "default";
        pinctrl-0 = <&example_pins>;
        status = "okay";
};

5. Build and artifact validation​

./build.sh kernel 2>&1 | tee /tmp/module-kernel-build.log
./build.sh pack

Confirm that the configuration and node reached the final output:

grep -E '<CONFIG_KEY>' out/*/*/kernel/build/.config 2>/dev/null
find out -type f \( -name '*.dtb' -o -name '*.ko' \) | sort
dtc -I dtb -O dts -o /tmp/final.dts <FINAL_DTB>
grep -n -A30 -B5 '<NODE_OR_COMPATIBLE>' /tmp/final.dts

6. Change boundaries​

  • Keep SoC resources and common defaults in bsp/configs/linux-5.15/*.dtsi.
  • Keep board pins, supplies, reset, child devices, and status in the board board.dts.
  • Never edit generated build output or a mirrored symlink tree directly.
  • Evaluate shared changes against every product that includes the common DTSI.