well, I struggled a little bit with these i2c dts files, too, but it didn't work...
so, I created a dts file with software i2c (i2c-gpio) for my hardware rtc i2c module:
// Overlay for i2c_gpio bitbanging host bus.
/dts-v1/;
/plugin/;
/ {
compatible = "amlogic,meson-gxbb";
fragment@0 {
target-path = "/";
__overlay__ {
i2c_gpio: i2c@2 {
compatible = "i2c-gpio";
gpios = <&gpio 82 0 /* sda */
&gpio 83 0 /* scl */
>;
i2c-gpio,delay-us = <2>; /* ~100 kHz */
#address-cells = <1>;
#size-cells = <0>;
ds3231: rtc@68 {
status = "okay";
compatible = "ds3231";
reg = <0x68>;
};
};
};
};
};
according to gpioinfo and the banana pi m5 wiki, the CON1-P03 is the I2C_M2_SDA and CON1-P05 is the I2C_M2_SCL.
line 81: "CON1-P26" unused input active-high
line 82: "CON1-P03" unused input active-high
line 83: "CON1-P05" unused input active-high
line 84: "CON1-P32" unused input active-high
After this, I have:
root@bpim5:~# i2cdetect -l
i2c-0 i2c DesignWare HDMI I2C adapter
i2c-1 i2c i2c@2 I2C adapter
root@bpim5:~# i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- UU -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
(the UU was 0x68, but it's currently used by the rtc module)
so, when I load the rtc_ds1307.ko kernel module, it automatically detects the device and the /dev/rtc1 appears...
