Difference between revisions of "Spi device tree source code"

Revision as of 22:49, 12 August 2022

2022-08-11 Thursday

Notes on SPI device tree source, with goal to add SPI device to modified RPi Pico DTS files, which build firmware to run on Sparkfun DEV-18288 board. An interesting link at Nordic Semi documentation pages, link to page which mentions Synopsis as designer of designware-spi device bindings and related bindings is:

• https://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.5.1/zephyr/reference/devicetree/bindings.html

NEED TO INVESTIGATE files in following Zephyr SDK directories:

`zephyr/soc/arm/rpi_pico` and `zephyr/soc/arm/rpi_pico/rp2`

^ SPI dts examples from Zephyr boards

In Zephyr RTOS' supported board dts files we find SPI peripherals defined for several boards. Here are excerpts

Excerpt 1 - zephyr/boards/arm/sparkfun_thing_plus_nrf9160/sparkfun_thing_plus_nrf9160_common.dts

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&spi3 {
        compatible = "nordic,nrf-spim";
        status = "okay";
        cs-gpios = <&gpio0 7 GPIO_ACTIVE_LOW>;
        pinctrl-0 = <&spi3_default>;
        pinctrl-1 = <&spi3_sleep>;
        pinctrl-names = "default", "sleep";
        w25q32jv: w25q32jv@0 {
                compatible = "jedec,spi-nor";
                label = "W25Q32JV";
                reg = <0>;
                spi-max-frequency = <40000000>;
                wp-gpios = <&gpio0 8 GPIO_ACTIVE_LOW>;
                hold-gpios = <&gpio0 10 GPIO_ACTIVE_LOW>;
                size = <0x2000000>;
                has-dpd;
                t-enter-dpd = <3000>;
                t-exit-dpd = <30000>;
                jedec-id = [ ef 40 16 ];
        };
};

a

 81         spi3_default: spi3_default {
 82                 group1 {
 83                         psels = <NRF_PSEL(SPIM_SCK, 0, 11)>,
 84                                 <NRF_PSEL(SPIM_MOSI, 0, 9)>,
 85                                 <NRF_PSEL(SPIM_MISO, 0, 28)>;
 86                 };
 87         };
 88 
 89         spi3_sleep: spi3_sleep {
 90                 group1 {
 91                         psels = <NRF_PSEL(SPIM_SCK, 0, 11)>,
 92                                 <NRF_PSEL(SPIM_MOSI, 0, 9)>,
 93                                 <NRF_PSEL(SPIM_MISO, 0, 28)>;
 94                         low-power-enable;
 95                 };
 96         };

^ edit point dts excerpt 2

Excerpt 2 - zephyr/boards/arm/96b_carbon_nrf51/96b_carbon_nrf51.dts and 96b_carbon_nrf51-pinctrl.dtsi

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&spi1 {
        compatible = "nordic,nrf-spis";
        status = "okay";
        def-char = <0x00>;

        pinctrl-0 = <&spi1_default>;
        pinctrl-names = "default";
        bt-hci@0 {
                compatible = "zephyr,bt-hci-spi-slave";
                reg = <0>;
                irq-gpios = <&gpio0 28 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)>;
        };
};

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        spi1_default: spi1_default {
                group1 {
                        psels = <NRF_PSEL(SPIS_SCK, 0, 7)>,
                                <NRF_PSEL(SPIS_MOSI, 0, 0)>,
                                <NRF_PSEL(SPIS_MISO, 0, 30)>,
                                <NRF_PSEL(SPIS_CSN, 0, 25)>;
                };
        };

^ edit point dts excerpt 3

Excerpt 3 - zephyr/boards/arm/stm32l562e_dk/stm32l562e_dk_common.dts and stm32l562e_dk_common.dtsi

Looks like pin control names value 'default'
may be defined in Kconfig.default for this board . . .

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&spi1 {
        pinctrl-0 = <&spi1_sck_pg2 &spi1_miso_pg3 &spi1_mosi_pg4>;
        pinctrl-names = "default";
        cs-gpios = <&gpiog 5 (GPIO_ACTIVE_HIGH | GPIO_PULL_UP)>;
        status = "okay";

        spbtle-rf@0 {
                compatible = "zephyr,bt-hci-spi";
                reg = <0>;
                irq-gpios = <&gpiog 6 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)>;
                reset-gpios = <&gpiog 8 (GPIO_ACTIVE_LOW | GPIO_PULL_UP)>;
                spi-max-frequency = <2000000>;
                label = "SPBTLE-RF";
        };
};

^ edit point dts excerpt 4

Excerpt 4 -

^ edit point dts excerpt 5

Excerpt 5 -

^ edit point dts excerpt 5

From the zephyr/boards/arm/rpi_pico/doc/index.rst file:

== [[#top|^]] edit point dts excerpt 5 ==
 37      Raspberry Pi Pico (Image courtesy of Raspberry Pi)
 38 
 39 Supported Features
 40 ==================
 41 
 42 The rpi_pico board configuration supports the following
 43 hardware features:
 44 
 45 .. list-table::
 46    :header-rows: 1
 47 
 48    * - Peripheral
 49      - Kconfig option
 50      - Devicetree compatible
 51    * - NVIC
 52      - N/A
 53      - :dtcompatible:`arm,v6m-nvic`
 54    * - UART
 55      - :kconfig:option:`CONFIG_SERIAL`
 56      - :dtcompatible:`rpi,pico-uart`
 57    * - GPIO
 58      - :kconfig:option:`CONFIG_GPIO`
 59      - :dtcompatible:`rpi,pico-gpio`
 60    * - I2C
 61      - :kconfig:option:`CONFIG_I2C`
 62      - :dtcompatible:`snps,designware-i2c`
 63    * - USB Device
 64      - :kconfig:option:`CONFIG_USB_DEVICE_STACK`
 65      - :dtcompatible:`raspberrypi,pico-usbd`
 66    * - HWINFO
 67      - :kconfig:option:`CONFIG_HWINFO`
 68      - N/A
 69 
 70 Programming and Debugging
 71 *************************
 72 
 73 Flashing

There is a clue here on line 62 "- :dtcompatible:`snps,designware-i2c`". This is for I2C, but a search via startpage.com for "snps,designware-spi" gives a first or near first result of:

• https://docs.zephyrproject.org/3.1.0/build/dts/api/bindings/spi/snps%2Cdesignware-spi.html

This still leaves the open question, where are RPi Pico's I2C and SPI driver implementations in Zephyr RTOS release 3.1.0?

^ YAML device bindings files

To support a typical development kit or custom board with multiple peripherals we need a device bindings file comparable to this ... bindings file:

1. ~/projects-sandbox/workspace-for-rpi/zephyr/boards/arm/nrf9160dk_nrf9160/nrf9160dk_nrf9160.yaml

identifier: nrf9160dk_nrf9160
name: nRF9160-DK-NRF9160
type: mcu 
arch: arm 
toolchain:
  - gnuarmemb
  - xtools
  - zephyr
ram: 88
flash: 256 
supported:
  - arduino_gpio
  - arduino_i2c
  - gpio
  - i2c
  - pwm
  - spi
  - watchdog
  - counter

Or possibly this bindings file by Jared Wolff of Circuit Dojo:

• https://github.com/circuitdojo/nrf9160-feather-examples-and-drivers/blob/v1.7.x/boards/arm/cd_test_board/cd_test_board.yaml

^ STMicro device tree SPI documentation

The following STMicro article goes into good detail on their SPI controllers in STM32Fxx family parts, and even gives device tree excerpts. These apparently are used in Linux based projects where Linux kernel and OS run on a 32-bit ST MCU.

• https://wiki.st.com/stm32mpu/wiki/SPI_device_tree_configuration

• https://wiki.st.com/stm32mpu/wiki/SPI_device_tree_configuration#cite_note-spi-controller.yaml-3

A device tree excerpt from the first link just above:

spi1: spi@44004000 {
	#address-cells = <1>;
	#size-cells = <0>;
	compatible = "st,stm32h7-spi";
	reg = <0x44004000 0x400>;
	interrupts = <GIC_SPI 35 IRQ_TYPE_LEVEL_HIGH>;
	clocks = <&rcc SPI1_K>;
	resets = <&rcc SPI1_R>;
	dmas = <&dmamux1 37 0x400 0x05>,
	       <&dmamux1 38 0x400 0x05>;
	dma-names = "rx", "tx";
	power-domains = <&pd_core>;
	status = "disabled";
};

Warning white.png Warning
This device tree part is related to STM32 microprocessors. It must be kept as is, without being modified by the end-user. 

^ RaspberryPi resources for developers

A good introduction to device tree:

• https://github.com/shellpress/raspberrypi/blob/master/configuration/device-tree.md

Github pull request comments requesting board support for RPi Pico:

• https://github.com/zephyrproject-rtos/zephyr/pull/33172#issuecomment-798885034

A forum post by someone attempting to add a SPI device to a RaspberryPi device tree file, though not RP2040 based board:

• https://forums.raspberrypi.com/viewtopic.php?t=274259