Hello all, This is an attempt to add MikroBUS addon support using the approach described by Grove connector patch series [0]. The patch series tests out 2 addon boards + pwm and GPIO on the MikroBUS connector. The boards used are GPS3 Click (for UART) [1] and Weather Click (for I2C) [2]. Additionally, I have tested relative GPIO numbering using devicetree nexus nodes [3]. The patch series does not attempt to do any dynamic discovery for 1-wire eeprom MikroBUS addon boards, nor does it provide any sysfs entry for board addition/removal. The connector driver might include them after the basic support is ironed out, but the existing patches for dynamic overlays work fine. The patch series has been tested on BeaglePlay [4]. I will now go over individual parts of the patch series, but for a better picture of the approach, it would be best to checkout [0] first. MikroBUS connector driver ------------------------- Just a stub platform driver for now. Will be extended in the future for dynamic board discovery using 1-wire eeprom present in some MikroBUS addon boards. While it is a stub driver, disabling it will make the GPIO connector nexus node unreachable (any driver attempting to use it will enter differed probing). So it is required. MikroBUS connector Devicetree ------------------------------ The connector devicetree defines the MikroBUS GPIO nexus node. This allows using pin numbering relative to MikroBUS connector pins in the addon boards overlay. Currently, the patch uses a clockwise numbering: 0: PWM 1: INT 2: RX 3: TX 4: SCL 5: SDA 6: MOSI 7: MISO 8: SCK 9: CS 10: RST 11: AN Additionally, in case PWM pin is not using channel 0, a nexus node for pwm should also be used and go in the connector devicetree. MikroBUS connector symbols overlay ---------------------------------- To make an overlay generic we need a standard name scheme which we use across base boards. For the connector pins the pinmux phandle shall be: <connector-name>_<pin-name>_mux_<pin-function> For the parent provider phandle, we use a similar naming scheme: <connector-name>_<pin-name>_<pin-function> For GPIO controller, I am using `MIKROBUS_GPIO` name since with nexus nodes, we do not need to define individual pin gpio controllers. The string symbols can be replaced with phandles once [5] is accepted. That will make connector stacking much simpler. MikroBUS addon board overlay ---------------------------- The patch puts the addon board overlays in their own directory. I am using the following naming scheme for MikroBUS addon boards: <vendor>-<product_id>.dtso Mikroe [6] lists this for all boards in their website, but I am not sure if other vendors have a product_id. This naming also makes future dynamic discovery easier, since click id spec [7] contains vendor_id and product_id in the header. Usage ----- So what does this all look like? Let's take an example of a BeaglePlay with one MikroBUS connectors for which we have physically attached a Wather click module to the first connector. Doing ahead of time command-line DT overlay application: ./fdtoverlay \ -o output.dtb \ -i k3-am625-beagleplay.dtb \ k3-am625-beagleplay-mikrobus-connector0.dtbo mikroe-5761.dtbo Open Items ---------- - SPI Support: Currently SPI dt requires `reg` property to specify the chipselect to use. This, makes the SPI device overlay dependent on the SPI controller. Thus for SPI support, we need a way to allow defining SPI chipselect relative to MikroBUS pins, and not the actual device controller. One possible solution is to introduce something like `named-reg` and allow selecting the chipselect by string array. But this probably requires more discussion so I have left out SPI support for now. NOTE: pins other than the CS MikroBUS pin can be used as chipselect. See [8]. - Controller symbol duplication The current symbol scheme has multiple symbols for the same underlying controller (Eg: MIKROBUS_SCL_MUX_I2C_SCL and MIKROBUS_SDA_MUX_I2C_SDA) point to the same i2c controller. I think both of them will always use the same i2c controller, but maybe there are some exceptions? So I have left it as it is for this patch series. The same thing also applies to UART and SPI. NOTE: with the use of nexus node for GPIO, the GPIO controller symbol will be the same for all pins. - Nexus node dt-bindings I am not quite sure how to deal with the nexus node properties (#gpio-cells, gpio-map, gpio-map-mask, gpio-map-pass-thru) since they seem to conflict with upstream gpio schema (gpio-controller is a dependency of #gpio-cells). [0]: https://lore.kernel.org/linux-arm-kernel/20240702164403.29067-1-afd@xxxxxx/ [1]: https://www.mikroe.com/gps-3-click [2]: https://www.mikroe.com/weather-click [3]: https://devicetree-specification.readthedocs.io/en/v0.3/devicetree-basics.html#nexus-nodes-and-specifier-mapping [4]: https://www.beagleboard.org/boards/beagleplay [5]: https://lore.kernel.org/r/20240902-symbol-phandle-v1-0-683efb2a944b@xxxxxxxxxxxxxxx [6]: https://www.mikroe.com/ [7]: https://github.com/MikroElektronika/click_id [8]: https://www.mikroe.com/spi-extend-click Signed-off-by: Ayush Singh <ayush@xxxxxxxxxxxxxxx> --- Ayush Singh (7): dt-bindings: connector: Add MikorBUS connector mikrobus: Add mikrobus driver dts: ti: k3-am625-beagleplay: Enable mikroBUS connector dts: ti: beagleplay: Add mikrobus connector symbols addon_boards: Add addon_boards plumbing addon_boards: mikrobus: Add Weather Click addon_boards: mikrobus: Add GPS3 Click Fabien Parent (1): rust: kernel: Add Platform device and driver abstractions .../bindings/connector/mikrobus-connector.yaml | 40 +++ Kbuild | 1 + Kconfig | 2 + MAINTAINERS | 8 + addon_boards/Kconfig | 16 + addon_boards/Makefile | 3 + addon_boards/mikrobus/Makefile | 4 + addon_boards/mikrobus/mikroe-1714.dtso | 28 ++ addon_boards/mikrobus/mikroe-5761-i2c.dtso | 28 ++ arch/arm64/boot/dts/ti/Makefile | 1 + .../k3-am625-beagleplay-mikrobus-connector0.dtso | 49 +++ arch/arm64/boot/dts/ti/k3-am625-beagleplay.dts | 53 ++- drivers/misc/Kconfig | 17 + drivers/misc/Makefile | 1 + drivers/misc/mikrobus.rs | 32 ++ rust/bindings/bindings_helper.h | 1 + rust/kernel/lib.rs | 1 + rust/kernel/platform.rs | 380 +++++++++++++++++++++ 18 files changed, 659 insertions(+), 6 deletions(-) --- base-commit: 9aaeb87ce1e966169a57f53a02ba05b30880ffb8 change-id: 20240826-mikrobus-dt-52eaaadd0b1f Best regards, -- Ayush Singh <ayush@xxxxxxxxxxxxxxx>
