Date: Mon, 18 Mar 2024 13:22:39 +0100
From: "Michael Walle" <mwalle@...nel.org>
To: "Ayush Singh" <ayushdevel1325@...il.com>, "open list"
 <linux-kernel@...r.kernel.org>
Cc: <jkridner@...gleboard.org>, <robertcnelson@...gleboard.org>,
 <lorforlinux@...gleboard.org>, "Rob Herring" <robh@...nel.org>, "Krzysztof
 Kozlowski" <krzysztof.kozlowski+dt@...aro.org>, "Conor Dooley"
 <conor+dt@...nel.org>, "Nishanth Menon" <nm@...com>, "Vignesh Raghavendra"
 <vigneshr@...com>, "Tero Kristo" <kristo@...nel.org>, "Derek Kiernan"
 <derek.kiernan@....com>, "Dragan Cvetic" <dragan.cvetic@....com>, "Arnd
 Bergmann" <arnd@...db.de>, "Greg Kroah-Hartman"
 <gregkh@...uxfoundation.org>, "Vaishnav M A" <vaishnav.a@...com>, "Mark
 Brown" <broonie@...nel.org>, "Johan Hovold" <johan@...nel.org>, "Alex
 Elder" <elder@...nel.org>, "open list:OPEN FIRMWARE AND FLATTENED DEVICE
 TREE BINDINGS" <devicetree@...r.kernel.org>, "moderated list:ARM/TEXAS
 INSTRUMENTS K3 ARCHITECTURE" <linux-arm-kernel@...ts.infradead.org>, "open
 list:SPI SUBSYSTEM" <linux-spi@...r.kernel.org>, "moderated list:GREYBUS
 SUBSYSTEM" <greybus-dev@...ts.linaro.org>, "Vaishnav M A"
 <vaishnav@...gleboard.org>
Subject: Re: [PATCH v4 1/5] dt-bindings: misc: Add mikrobus-connector

On Sun Mar 17, 2024 at 8:37 PM CET, Ayush Singh wrote:
> Add DT bindings for mikroBUS interface. MikroBUS is an open standard
> developed by MikroElektronika for connecting add-on boards to
> microcontrollers or microprocessors.
>
> mikroBUS is a connector and does not have a controller. Instead the
> software is responsible for identification of board and setting up /
> registering uart, spi, i2c, pwm and other buses. Thus it needs a way to
> get uart, spi, i2c, pwm and gpio controllers / adapters.
>
> A mikroBUS addon board is free to leave some of the pins unused which
> are marked as NC or Not Connected.
>
> Some of the pins might need to be configured as GPIOs deviating from their
> reserved purposes Eg: SHT15 Click where the SCL and SDA Pins need to be
> configured as GPIOs for the driver (drivers/hwmon/sht15.c) to work.
>
> For some add-on boards the driver may not take care of some additional
> signals like reset/wake-up/other. Eg: ENC28J60 click where the reset line
> (RST pin on the mikrobus port) needs to be pulled high.
>
> Here's the list of pins in mikroBUS connector:
> Analog - AN
> Reset - RST
> SPI Chip Select - CS
> SPI Clock - SCK
> SPI Master Input Slave Output - MISO
> SPI Master Output Slave Input - MOSI
> VCC-3.3V power - +3.3V
> Reference Ground - GND
> PWM - PWM output
> INT - Hardware Interrupt
> RX - UART Receive
> TX - UART Transmit
> SCL - I2C Clock
> SDA - I2C Data
> +5V - VCC-5V power
> GND - Reference Ground
>
> Additionally, some new mikroBUS boards contain 1-wire EEPROM that contains
> a manifest to describe the addon board to provide plug and play
> capabilities.
>
> Link: https://www.mikroe.com/mikrobus
> Link:
> https://download.mikroe.com/documents/standards/mikrobus/mikrobus-standard-specification-v200.pdf
> mikroBUS specification
> Link: https://www.mikroe.com/sht1x-click SHT15 Click
> Link: https://www.mikroe.com/eth-click ENC28J60 Click
> Link: https://www.mikroe.com/clickid ClickID
>
> Co-developed-by: Vaishnav M A <vaishnav@...gleboard.org>
> Signed-off-by: Vaishnav M A <vaishnav@...gleboard.org>
> Signed-off-by: Ayush Singh <ayushdevel1325@...il.com>
> ---
>  .../connector/mikrobus-connector.yaml         | 113 ++++++++++++++++++

See also
https://lore.kernel.org/r/YmFo+EntwxIsco%2Ft@robh.at.kernel.org/

Looks like this proposal doesn't have the subnodes. How do you
attach a kernel driver to it's spi port for example? Only through
the manifest files?

-michael

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