Re: [greybus-dev] [RFC PATCH v2 3/3] Add Device Tree Bindings for mikroBUS port

On Tue, Aug 18, 2020 at 6:48 AM Vaishnav M A vaishnav@beagleboard.org wrote:

This patch adds device tree bindings for the mikroBUS port, device tree overlays for the mikrobus Port on the BeagleBoard.org PocketBeagle is available here : github.com/beagleboard/bb.org-overlays/blob/master/src/arm/PB-MIKROBUS-0.dts

Signed-off-by: Vaishnav M A vaishnav@beagleboard.org

.../bindings/misc/linux,mikrobus.txt | 81 +++++++++++++++++++ 1 file changed, 81 insertions(+) create mode 100644 Documentation/devicetree/bindings/misc/linux,mikrobus.txt

diff --git a/Documentation/devicetree/bindings/misc/linux,mikrobus.txt b/Documentation/devicetree/bindings/misc/linux,mikrobus.txt new file mode 100644 index 000000000000..99f75caf5f35 --- /dev/null +++ b/Documentation/devicetree/bindings/misc/linux,mikrobus.txt @@ -0,0 +1,81 @@ +mikroBUS add-on board socket

+Required properties: +- compatible: Must be "linux,mikrobus"

mikrobus is only a Linux thing? Just 'mikrobus-connector' is fine.

Are there versions of mikrobus spec/connectors? If so, then should probably include that into

+- i2c-adapter: phandle to the i2c adapter attached to the mikrobus socket. +- spi-master: spi bus number of the spi-master attached to the mikrobus socket. +- spi-cs: spi chip-select numbers corresponding to the chip-selects

•     on the mikrobus socket(0 -> chip select corresponding to CS pin
  

•     1 -> chip select corresponding to RST pin).
  

SPI and I2C need a common way to remap from host bus/cs to connector bus/cs including how to define the child devices and multiple instances.

+- serdev-controller: phandle to the uart port attached to the mikrobus socket.

'serdev' is a Linuxism. This also needs to be defined how child devices and multiple instances.

There's also a problem with the current serdev implementation that assigning a serial port to serdev or tty is a one time decision as probe time. So I don't think hotplug of a serial device will work today. But that's a Linux problem independent of the binding.

+- pwms: phandle to the pwm-controller corresponding to the mikroBUS PWM pin.

The PWM binding has a provider specific number of cells, so some translation is needed. Probably can define a 'pwm-map' property like gpio-map on this. More below.

+- mikrobus-gpios: gpios array corresponding to GPIOs on the mikroBUS port,

•             for targets not supporting the AN pin on the mikroBUS port as
  

•             GPIO, the length of the gpios array can be 11, otherwise it
  

•             should be 12.
  

We have 'gpio-map' binding already (it's in the DT spec) created for this purpose of remapping connector GPIO numbers to host GPIO numbers.

+- pinctrl-names: pinctrl state names to support additional pin usage/deviations

•            from mikroBUS socket standard usage, must be "default",
  

•            "pwm_default", "pwm_gpio", "uart_default", "uart_gpio",
  

•            "i2c_default", "i2c_gpio", "spi_default", "spi_gpio", these
  

•            pinctrl names should have corresponding pinctrl-N entries which
  

•            corresponds to the pinmux state for the pingroup, for example,
  

•            i2c_default corresponds to the state where the I2C pin group
  

•            (SCL,SDA) are configured in I2C mode and i2c_gpio mode corresponds
  

•            to the pinmux state where these pins are configured as GPIO.
  

+- pinctrl-N : pinctrl-(0-8) corresponds to the pinctrl states for the states described

•         above.
  

+Example:

•   mikrobus-0 {
  

•           compatible = "linux,mikrobus";
  

•           status = "okay";
  

•           pinctrl-names = "default", "pwm_default", "pwm_gpio",
  

•                           "uart_default", "uart_gpio", "i2c_default",
  

•                           "i2c_gpio", "spi_default", "spi_gpio";
  

•           pinctrl-0 = <
  

•                   &P2_03_gpio_input_pin
  

•                   &P1_04_gpio_pin
  

•                   &P1_02_gpio_pin
  

•           >;
  

•           pinctrl-1 = <&P2_01_pwm_pin>;
  

•           pinctrl-2 = <&P2_01_gpio_pin>;
  

•           pinctrl-3 = <
  

•                   &P2_05_uart_pin
  

•                   &P2_07_uart_pin
  

•           >;
  

•           pinctrl-4 = <
  

•                   &P2_05_gpio_pin
  

•                   &P2_07_gpio_pin
  

•           >;
  

•           pinctrl-5 = <
  

•                   &P2_09_i2c_pin
  

•                   &P2_11_i2c_pin
  

•           >;
  

•           pinctrl-6 = <
  

•                   &P2_09_gpio_pin
  

•                   &P2_11_gpio_pin
  

•           >;
  

•           pinctrl-7 = <
  

•                   &P1_12_spi_pin
  

•                   &P1_10_spi_pin
  

•                   &P1_08_spi_sclk_pin
  

•                   &P1_06_spi_cs_pin
  

•           >;
  

•           pinctrl-8 = <
  

•                   &P1_12_gpio_pin
  

•                   &P1_10_gpio_pin
  

•                   &P1_08_gpio_pin
  

•                   &P1_06_gpio_pin
  

•           >;
  

•           i2c-adapter = <&i2c1>;
  

•           spi-master = <0>;
  

•           spi-cs = <0 1>;
  

•           serdev-controller = <&uart4>;
  

•           pwms = <&ehrpwm1 0 500000 0>;
  

•           mikrobus-gpios = <&gpio1 18 0> , <&gpio0 23 0>,
  

•                                   <&gpio0 30 0> , <&gpio0 31 0>,
  

•                                   <&gpio0 15 0> , <&gpio0 14 0>,
  

•                                   <&gpio0 4 0> , <&gpio0 3 0>,
  

•                                   <&gpio0 2 0> , <&gpio0 5 0>,
  

•                                   <&gpio2 25 0>  , <&gpio2 3 0>;
  

•   };
  

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