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Date: Thu, 27 Aug 2020 09:45:23 -0600
From: Rob Herring <robh@...nel.org>
To: Vaishnav M A <vaishnav@...gleboard.org>
Cc: greybus-dev@...ts.linaro.org,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Arnd Bergmann <arnd@...db.de>, Johan Hovold <johan@...nel.org>,
elder@...nel.org,
Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
David Miller <davem@...emloft.net>,
Jason Kridner <jkridner@...gleboard.org>,
Drew Fustini <drew@...gleboard.org>,
robertcnelson@...gleboard.org, rajkovic@...roe.com,
chrisfriedt@...il.com, zoran.stojsavljevic@...il.com
Subject: Re: [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@...gleboard.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@...gleboard.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>;
> + };
> \ No newline at end of file
> --
> 2.25.1
>
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