Raspberry Pi DSI with STM32MP157F

[alchitry]

I'm trying to get a Raspberry Pi DSI display working with a custom board using a STM32MP157F.

From the wiki I have the following.

&dsi {
	status = "okay";

	ports {
		port@0 {
			reg = <0>;
			dsi_in: endpoint {
				remote-endpoint = <&ltdc_ep0_out>;
			};
		};

		port@1 {
			reg = <1>;
			dsi_out: endpoint {
				remote-endpoint = <&bridge_in>;
			};
		};
	};

	bridge@0 {
		compatible = "toshiba,tc358762";
		reg = <0>;
		vddc-supply = <&reg_rpi>;
		status = "okay";

		ports {
			#address-cells = <1>;
			#size-cells = <0>;

			port@0 {
				reg = <0>;
				bridge_in: endpoint {
					remote-endpoint = <&dsi_out>;
				};
			};
			port@1 {
				reg = <1>;
				bridge_out: endpoint {
					remote-endpoint = <&panel_in>;
				};
			};
		};
	};
};

/ {
	panel-rgb {
		/* Unknown; use a reasonably similar one */
		compatible = "powertip,ph800480t013-idf02";
		power-supply = <&reg_rpi>;
		status = "okay";

		port {
			panel_in: endpoint {
				remote-endpoint = <&bridge_out>;
			};
		};
	};
};

&i2c6 {
	reg_rpi: regulator@45 {
		compatible = "raspberrypi,7inch-touchscreen-panel-regulator";
		reg = <0x45>;
		vin-supply = <&v3v3>;
		status = "okay";
	};
};

&ltdc {
	default-on;
	status = "okay";

	port {
		ltdc_ep0_out: endpoint {
			remote-endpoint = <&dsi_in>;
		};
	};
};

In another file I have

	i2c6_pins_b: i2c6-1 {
		pins {
			pinmux = <STM32_PINMUX('Z', 2, AF2)>, /* I2C6_SCL */
				 <STM32_PINMUX('Z', 3, AF2)>; /* I2C6_SDA */
			bias-disable;
			drive-open-drain;
			slew-rate = <0>;
		};
	};

	i2c6_sleep_pins_b: i2c6-sleep-1 {
		pins {
			pinmux = <STM32_PINMUX('Z', 2, ANALOG)>, /* I2C6_SCL */
				 <STM32_PINMUX('Z', 3, ANALOG)>; /* I2C6_SDA */
		};
	};

and

&i2c6 {
	pinctrl-names = "default", "sleep";
	pinctrl-0 = <&i2c6_pins_b>;
	pinctrl-1 = <&i2c6_sleep_pins_b>;
	i2c-scl-rising-time-ns = <100>;
	i2c-scl-falling-time-ns = <7>;
	status = "okay";
};

I'm not seeing any action on the I2C lines so I'm not surprised the display isn't working.

The rest of my tree is basically from the stm32mp157f-dk2 which has includes that define the clock and power for i2c6 (double checked that).

Is there something more I need to do to enable it?

After boot I can see the following.

# dmesg | grep -i -e "drm" -e "ltdc" -e "dsi" -e "display" -e "panel"
[    0.127696] /soc/display-controller@5a001000: Fixed dependency cycle(s) with /soc/dsi@5a000000
[    0.128529] /soc/dsi@5a000000: Fixed dependency cycle(s) with /soc/dsi@5a000000/bridge@0
[    0.128581] /soc/dsi@5a000000: Fixed dependency cycle(s) with /soc/display-controller@5a001000
[    0.128657] /soc/dsi@5a000000/bridge@0: Fixed dependency cycle(s) with /soc/dsi@5a000000
[    0.139112] /soc/display-controller@5a001000: Fixed dependency cycle(s) with /soc/dsi@5a000000
[    0.152623] /soc/display-controller@5a001000: Fixed dependency cycle(s) with /soc/dsi@5a000000
[    0.152854] /soc/dsi@5a000000: Fixed dependency cycle(s) with /soc/dsi@5a000000/bridge@0
[    0.152903] /soc/dsi@5a000000: Fixed dependency cycle(s) with /soc/display-controller@5a001000
[    0.153381] /soc/dsi@5a000000/bridge@0: Fixed dependency cycle(s) with /soc/dsi@5a000000
[    0.156238] /soc/dsi@5a000000/bridge@0: Fixed dependency cycle(s) with /panel-rgb
[    0.156703] /panel-rgb: Fixed dependency cycle(s) with /soc/dsi@5a000000/bridge@0
[    4.206731] /panel-rgb: Fixed dependency cycle(s) with /soc/dsi@5a000000/bridge@0
[    4.220535] /soc/dsi@5a000000: Fixed dependency cycle(s) with /soc/dsi@5a000000/bridge@0
[    4.228565] /soc/dsi@5a000000/bridge@0: Fixed dependency cycle(s) with /panel-rgb
[    4.236008] /soc/dsi@5a000000/bridge@0: Fixed dependency cycle(s) with /soc/dsi@5a000000
[   10.012903] systemd[1]: Starting Load Kernel Module drm...
[   14.557772] platform 5a001000.display-controller: deferred probe pending
[   14.565563] platform panel-rgb: deferred probe pending
[   15.672916] [drm] Initialized etnaviv 1.4.0 20151214 for etnaviv on minor 0

I don't know why the probe is just pending?

I don't see a power supply named "reg_rpi" like I'd expect in /sys/class/regulator

[OlivierK · Accepted solution]

Hello @alchitry 

I have little experience in connecting Rpi display with STM32MP157, however you may try several things if not done yet.

- You mentioned that the I2C shows no activity on the lines. Have you tried to enable the driver i2c-dev and use i2c-tools to check that the I2C is functional .

https://wiki.st.com/stm32mpu/wiki/I2C_i2c-tools

Also a Wiki article related to Rpi display and DT config.

https://wiki.st.com/stm32mpu/wiki/Display_panels_hardware_components#Raspberry_Pi_7-22_Touch_-28MIPI-C2-AE_DSI-29

Regards,

Olivier