On 3/19/24 11:28, Krzysztof Kozlowski wrote:
On 18/03/2024 18:20, Ayush Singh wrote:On 3/18/24 17:52, Michael Walle wrote: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@xxxxxxxxxxxxxxx> Signed-off-by: Vaishnav M A <vaishnav@xxxxxxxxxxxxxxx> Signed-off-by: Ayush Singh <ayushdevel1325@xxxxxxxxx> --- .../connector/mikrobus-connector.yaml | 113 ++++++++++++++++++See also https://lore.kernel.org/r/YmFo+EntwxIsco%2Ft@xxxxxxxxxxxxxxxxxx/ 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? -michaelSo I looked at the Patch, and it seems the approach of fundamentally different than this PR. So, let me try to explain what this patch set does for an add-on board using SPI. The device tree defines the SPI controller associated with mikroBUS SPI pins. The driver on match queries and takes a reference to the SPI controller but does nothing with it. Once a mikroBUS add-on board is detected (by passing manifest using sysfs or reading from 1-wire EEPROM), the driver parses the manifest, and if it detects an SPI deviceAs I understood Mikrobus does not have EEPROM.
mikroBUS add-on boards do not need to have EEPROM, but they can have it. Simply put, EEPROM is not part of mikroBUS specification, but you will find a lot (especially newer) addon boards with support for EEPROM manifest.
Regardless, this patch actually does not contain any code for EEPROM support I have just mentioned it to give more context on why mikroBUS manifest is the focus of this patch instead of DT overlay or something else.
in manifest, it registers SPI device along with setting properties such as `chip_select`, `max_speed_hz`, `mode`, etc., which are defined in the manifest. On board removal, it unregisters the SPI device and waits for a new mikroBUS board to be detected again.You explained drivers, not hardware for DT.
Yes, I was replying to the question posed by Michael. Since this happens in the driver and not in the devicetree, I needed to explain the working of the driver:
> How do you attach a kernel driver to it's spi port for example?For more hardware side, the bindings are for mikrobus connector rather than for any addon board. Thus, while an addon board might not use some of the pins, the connector still needs to have all the pins and associated controllers.
It is also possible for SPI not to be used by a device, in which case, no SPI device is registered to the controller. It is also possible that the SPI pins will be used as normal GPIOs. Everything is identified from the manifest.Best regards, Krzysztof
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