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TWI / I2C 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:

  • I2C support
  • I2C device interface（/dev/i2c-*）
  • Allwinner TWI controller
  • TWI slave and slave EEPROM (when slave mode is required)

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.

&twi0 {
        clock-frequency = <400000>;
        pinctrl-names = "default", "sleep";
        pinctrl-0 = <&twi0_pins_a>;
        pinctrl-1 = <&twi0_pins_b>;
        /* Older drivers may use twi_drv_used control DMA；5.15 Need to check the current driver */
        status = "okay";

        eeprom@50 {
                compatible = "atmel,24c16";
                reg = <0x50>;
        };
};

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.