CounterPillow
commented
1 year ago Hi,
on SOQuartz you'll have several choices of I2C buses to activate:
- I2C2 pinmux M1
- I2C3 pinmux M0
here's an example of how to enable I2C2 with pinmux M1 (I didn't test this on actual hardware, just test compiled):
/dts-v1/;
/plugin/; /* Identifies this as an overlay */
&i2c2 { /* We are modifying the i2c2 node of the base tree */
/* Describe the pinmux as being pinmux m1 */
pinctrl-0 = <&i2c2m1_xfer>;
/* The next two are already set in the base tree we're overlaying onto,
* but dtc doesn't know this, so it emits warnings. Either way, they
* describe what the meaning of all the children's reg properties is. In
* this case, that the only cell in reg describes what address the device
* listens on.
*/
#address-cells = <1>;
#size-cells = <0>;
status = "okay"; /* Enable the I2C2 node of rk356x.dtsi */
};
/* Copied from rk3568-pinctrl.dtsi in the Linux kernel tree, with constants resolved
* We need to copy it from there because it gets omitted if there's no
* reference to it.
*/
&pinctrl {
pcfg_pull_none_smt: pcfg-pull-none-smt {
bias-disable;
input-schmitt-enable;
};
i2c2 {
i2c2m1_xfer: i2c2m1-xfer {
rockchip,pins =
/* i2c2_sclm1 */
<4 13 1 &pcfg_pull_none_smt>,
/* i2c2_sdam1 */
<4 12 1 &pcfg_pull_none_smt>;
};
};
};Save the file as enable-i2c2.dts, you can then compile the overlay with dtc -I dts -O dtb -@ -o enable-i2c2.dtbo enable-i2c2.dts. Place the resulting file in /boot/dtbo/, run sudo u-boot-update and reboot.
If you now wish to implement an I2C driver in userspace, please see the Linux kernel documentation on how to do that. If that's all you want to do, you can stop here.
However, be aware that for many devices, you don't even need to do this! The kernel may have a driver already and can expose it like any built-in device.
For example, here's the same overlay, but now we add a BMM150 magnetometer device to the description so that the kernel can load its driver for it (assuming it was compiled with said driver, CONFIG_BMC150_MAGN_I2C, Debian's kernel is):
/dts-v1/;
/plugin/; /* Identifies this as an overlay */
&i2c2 { /* We are modifying the i2c2 node of the base tree */
/* Describe the pinmux as being pinmux m1 */
pinctrl-0 = <&i2c2m1_xfer>;
/* The next two are already set in the base tree we're overlaying onto,
* but dtc doesn't know this, so it emits warnings. Either way, they
* describe what the meaning of all the children's reg properties is. In
* this case, that the only cell in reg describes what address the device
* listens on.
*/
#address-cells = <1>;
#size-cells = <0>;
status = "okay"; /* Enable the I2C2 node of rk356x.dtsi */
bmm150: magnetometer@10 { /* New child node with label "bmm150", address 0x10 */
compatible = "bosch,bmm150"; /* Identifier for the kernel to know what driver to load */
reg = <0x10>; /* Describe the I2C address as 0x10 (= decimal 16) */
/* What follows is the (optional) "mount matrix", which describes how the sensor is
* mounted in 3d space. In this example, we rotate it around z by 90°.
* See https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bindings/iio/mount-matrix.txt
* for more details.
*/
mount-matrix = "0", "-1", "0",
"1", "0", "0",
"0", "0", "1";
};
};
/* Copied from rk3568-pinctrl.dtsi in the Linux kernel tree, with constants resolved
* We need to copy it from there because it gets omitted if there's no
* reference to it.
*/
&pinctrl {
pcfg_pull_none_smt: pcfg-pull-none-smt {
bias-disable;
input-schmitt-enable;
};
i2c2 {
i2c2m1_xfer: i2c2m1-xfer {
rockchip,pins =
/* i2c2_sclm1 */
<4 13 1 &pcfg_pull_none_smt>,
/* i2c2_sdam1 */
<4 12 1 &pcfg_pull_none_smt>;
};
};
};The resulting magnetometer would then be handled by the IIO (industrial IO) subsystem, e.g. show up in /sys/bus/iio/devices.
This is of course just an example, for your I2C device you'd have to find the right compatible string and bindings. I can help you do that if you tell me what device it is.
Let me know if this resolves the issue for you, and if you need further assistance using your particular I2C device in the ideal way.
Gerriko
With gerriko having solved the SPI problem - has anyone made similar progress on I2C?
Starting to read the kernel/overlays/etc.
But it's not something I'm familiar with.