PocketBeagle MCP2515 SPI1 device tree overlay for Macchina adapter /opt/source/bb.org-overlays/src/arm/PB-MCP2515.dts

PB-MCP2515.dts

/dts-v1/;
/plugin/;

#include <dt-bindings/gpio/gpio.h>
#include <dt-bindings/pinctrl/am33xx.h>
#include <dt-bindings/interrupt-controller/irq.h>

/*

Macchina SPI0 for SWCAN MCP2515 is PocketBeagle SPI1

Macchina PB adapter J3 is PB P1
Macchina PB adapter J2 is next to J3 / PB P1

Macchina PB adapter J4 is PB P2
Macchina PB adapter J1 is next to J4 / PB P2

https://github.com/macchina/pocketbeagle-adapter-hardware/blob/master/SCH-01010%20R0%20SCHEM_RELEASE.PDF
https://github.com/macchina/m2-hardware/tree/master/M2-B
https://github.com/macchina/m2-hardware/blob/master/M2-B/Interface%20Board%20PCB.pdf

M2 J3 is plugs into PB adapter J2, next to PB P1 (which is PB adapter J3)
M2 J4 is plugs into PB adapter J1, next to PB P2 (which is PB adapter J4)

M2 J4.20: SWC nINT <-> P2.8
M2 J3.6 : SWC_nRESET  <-> P2.32
M2 J4.9 : SWC_M0  <-> P2.6
M2 J4.28: SWC_M1  <-> P2.18
M2 J3.30: SWC_CLK  <-> NC
M2 J4.25: SWC_SOF  <-> NC
M2 J4.29: SWC_nRX0BF  <-> NC
M2 J4.30: SWC_nRX1BF  <-> NC

M2 J4.27: SPI0_CLK  <-> PB adapter J2.27: SPI1_CLK
M2 J4.24: SPI0_MISO <-> PB adapter J2.24: SPI1_MISO
M2 J4.26: SPI0_MOSI <-> PB adapter J2.26: SPI1_MOSI
M2 J3.25: SPI0_nCS3 <-> PB adapter J1.25: SPI1_CS

PB adapter J4.25: SPI1_MOSI <-> PB 2.25: SPI1_MOSI
PB adapter J4.27: SPI1_MISO <-> PB 2.27: SPI1_MISO
PB adapter J4.29: SPI1_CLK  <-> PB 2.29: SPI1_CLK
PB adapter J4.31: SPI1_CS   <-> PB 2.31: SPI1_CS

1006 Signals    1006 headers2    1010/PB header
SWC nRESET      J3P6             P2-32
SPI0_nCS3       J3P25            P2-31
SPI0 MISO       J4P24            P2-27
SPI0 MOSI       J4P26            P2-25
SPI0 CLK        J4P27            P2-29
SWC nINT        J4P20            P2-8
SWC nRX0BF      J4P29            NC
SWC nRX1BF      J4P30            NC
SWC SOF         J4P25            NC
SWC CLK         J3P30            NC
SWC M0          J4P9             P2-6
SWC M1          J4P28            P2-18

*/


/ {
        fragment@0 {
                target = <&ocp>;
                __overlay__ {
/* 
M2 J4.20: SWC nINT <-> P2.8 <&gpio1 28 0>, needs GPIO input
M2 J3.6 : SWC_nRESET  <-> P2.32 GPIO 112 / PRU0.2, <&gpio3 16 0>, needs GPIO OUTPUT
M2 J4.9 : SWC_M0  <-> P2.6
M2 J4.28: SWC_M1  <-> P2.18
*/
                        P2_08_pinmux { status = "disabled"; };  /* SWC nINT */
                        P2_32_pinmux { status = "disabled"; };  /* SWC nRESET */
                        P2_25_pinmux { status = "disabled"; };  /* MOSI - gpio1_9 */
                        P2_27_pinmux { status = "disabled"; };  /* MISO - gpio1_8 */
                        P2_29_pinmux { status = "disabled"; };  /* CLK - gpio0_7 */
                        P2_31_pinmux { status = "disabled"; };  /* CS - gpio0_19 */
                };
	};

        fragment@1 {
		target = <&spi1>;
		__overlay__ {
			status = "okay";
			spidev@1 {
				status = "disabled";
			};
		};

	};

        fragment@2 {
                target = <&spi1>;
                __overlay__ {
                        status = "okay";
                        pinctrl-names = "default";
/* 
M2 J4.20: SWC nINT <-> P2.8 <&gpio1 28 0>, needs GPIO input
M2 J3.6 : SWC_nRESET  <-> P2.32 GPIO 112 / PRU0.2, <&gpio3 16 0>, needs GPIO OUTPUT
M2 J4.9 : SWC_M0  <-> P2.6 GPIO 57, needs GPIO OUTPUT
M2 J4.28: SWC_M1  <-> P2.18 GPIO 47, needs GPIO OUTPUT
*/
                        pinctrl-0 = <
                                /* connected to MCP2515 pin 19 _RESET 
                                   hopefully pullup will enable the chip */
                                &P2_32_gpio_pu_pin
                                /* SWC nINT */
                                &P2_08_gpio_input_pin 
                                /* SPI1 */
                                &P2_31_spi_cs_pin
                                &P2_29_spi_sclk_pin
                                &P2_27_spi_pin
                                &P2_25_spi_pin
                        >;

                        channel@0{ status = "disabled"; };
                        channel@1{ status = "disabled"; };
                };
        };


        fragment@3 {
		target = <&am33xx_pinmux>;
		__overlay__ {
			mcp2515_int: mcp2515_int {
				pinctrl-single,pins = < 0x00c 0x37 >;
			};
		};
	};

	fragment@4 {
		target-path = "/";
		__overlay__ {
			mcp2515_clock: mcp2515_clock {
				compatible = "fixed-clock";
				#clock-cells = <0>;
				clock-frequency = <8000000>;
			};
		};
	};

	fragment@5 {

		target = <&spi1>;
		__overlay__ {
			#address-cells = <1>;
			#size-cells = <0>;
			can0: mcp2515@0 {
				status = "okay";
				reg = <0>;
				compatible = "microchip,mcp2515";
				pinctrl-names = "default";
				pinctrl-0 = <&mcp2515_int>;
				spi-max-frequency = <10000000>;
				interrupt-parent = <&gpio1>;
				interrupts = <3 2>;
				clocks = <&mcp2515_clock>;

				mcp251x,oscillator-frequency = <8000000>;
				mcp251x,irq-gpios = <&gpio1 28 0>;
				mcp251x,stay-awake = <1>;
				mcp251x,enable-clkout = <1>;
			};
		};
	};

	__overrides__ {
		oscillator = <&mcp2515_clock>,"clock-frequency:0";
		spimaxfrequency = <&can0>,"spi-max-frequency:0";
		interrupt = <&mcp2515_int>,"pinctrl-single,pins:0",<&can0>,"interrupts:0";
	};

};

more information in this gist:
https://gist.github.com/pdp7/283e39a63645e47c3ed86b8207bac79d

The active-low MCP2515 RESET pin is connected to PocketBeagle P2.32.

I have confirmed that P2.32 is 3.3V so the pull-up configuration in this device tree overlay does seem to work.