mgmt: ec_host_cmd: add SPI SMT32 backend

Add support for SPI host command backend for STM32 chips family.

Unfortunately, the current SPI API can't be used to handle the host
commands communication. The main issues are unknown command size sent
by the host(the SPI transaction sends/receives specific number of bytes)
and need to constant sending status byte(the SPI module is enabled and
disabled per transaction). Thus the SPI backend includes basic SPI STM32
driver adjusted to host command specification.

Signed-off-by: Dawid Niedzwiecki <[email protected]>

doc/services/device_mgmt/ec_host_cmd.rst

@@ -36,13 +36,44 @@ one backend layer.
 .. image:: ec_host_cmd_shi.png
    :align: center
 
+Another case is SPI. Unfortunately, the current SPI API can't be used to handle the host commands
+communication. The main issues are unknown command size sent by the host (the SPI transaction
+sends/receives specific number of bytes) and need to constant sending status byte (the SPI module
+is enabled and disabled per transaction). It forces implementing the SPI driver within a backend,
+as it is done for SHI. That means a SPI backend has to implemented per chip family. However, it
+can be changed in the future once the SPI API is extended to host command needs.
+
+That approach requires configuring the SPI dts node in a special way. The main compatible string of
+a SPI node has changed to use the Host Command version of a SPI driver. The rest of the properties
+should be configured as usual. Example of the SPI node for STM32:
+
+.. code-block:: devicetree
+
+   &spi1 {
+           /* Change the compatible string to use the Host Command version of the
+            * STM32 SPI driver
+            */
+           compatible = "st,stm32-spi-host-cmd";
+           status = "okay";
+
+           dmas = <&dma2 3 3 0x38440 0x03>,
+                <&dma2 0 3 0x38480 0x03>;
+           dma-names = "tx", "rx";
+           /* This field is used to point at our CS pin */
+           cs-gpios = <&gpioa 4 (GPIO_ACTIVE_LOW | GPIO_PULL_UP)>;
+   };
+
+The chip that runs Zephyr is a SPI slave and the `cs-gpios` property is used to point our CS pin.
+For the SPI, it is required to set the backend chosen node ``zephyr,host-cmd-spi-backend``.
+
 The supported backend and peripheral drivers:
 
 * Simulator
 * SHI - ITE and NPCX
 * eSPI - any eSPI slave driver that support :kconfig:option:`CONFIG_ESPI_PERIPHERAL_EC_HOST_CMD` and
   :kconfig:option:`CONFIG_ESPI_PERIPHERAL_CUSTOM_OPCODE`
 * UART - any UART driver that supports the asynchronous API
+* SPI - STM32
 
 Initialization
 **************
@@ -54,6 +85,7 @@ initializes the host command subsystem by calling :c:func:`ec_host_cmd_init`:
 * ``zephyr,host-cmd-espi-backend``
 * ``zephyr,host-cmd-shi-backend``
 * ``zephyr,host-cmd-uart-backend``
+* ``zephyr,host-cmd-spi-backend``
 
 If no backend chosen node is configured, the application must call the :c:func:`ec_host_cmd_init`
 function directly. This way of initialization is useful if a backend is chosen in runtime

dts/bindings/spi/st,stm32-spi-host-cmd.yaml

@@ -0,0 +1,10 @@
+# Copyright (c) 2023 Google LLC
+# SPDX-License-Identifier: Apache-2.0
+
+description: |
+        Host Command version of STM32 SPI controller.
+        All properties are the same, but a different driver is used.
+
+compatible: "st,stm32-spi-host-cmd"
+
+include: st,stm32-spi.yaml

dts/bindings/spi/st,stm32h7-spi-host-cmd.yaml

@@ -0,0 +1,10 @@
+# Copyright (c) 2023 Google LLC
+# SPDX-License-Identifier: Apache-2.0
+
+description: |
+        Host Command version of STM32H7 SPI controller.
+        All properties are the same, but a different driver is used.
+
+compatible: "st,stm32h7-spi-host-cmd"
+
+include: st,stm32h7-spi.yaml

subsys/mgmt/ec_host_cmd/Kconfig

@@ -26,6 +26,7 @@ config EC_HOST_CMD_HANDLER_TX_BUFFER_SIZE
 	default 0 if EC_HOST_CMD_BACKEND_ESPI
 	default 0 if EC_HOST_CMD_BACKEND_SHI
 	default 256 if EC_HOST_CMD_BACKEND_UART
+	default 552 if EC_HOST_CMD_BACKEND_SPI
 	default 256
 	help
 	  Buffer size in bytes for TX buffer defined by the host command handler.
@@ -38,6 +39,7 @@ config EC_HOST_CMD_HANDLER_RX_BUFFER_SIZE
 	default 256 if EC_HOST_CMD_BACKEND_ESPI
 	default 0 if EC_HOST_CMD_BACKEND_SHI
 	default 544 if EC_HOST_CMD_BACKEND_UART
+	default 544 if EC_HOST_CMD_BACKEND_SPI
 	default 256
 	help
 	  Buffer size in bytes for TX buffer defined by the host command handler.
@@ -56,7 +58,7 @@ config EC_HOST_CMD_HANDLER_PRIO
 
 config EC_HOST_CMD_INIT_PRIORITY
 	int "Initialization priority"
-	default 60
+	default 80
 	range 0 99
 	help
 	  Initialization priority for Host Command. It must be higher than the initialization

subsys/mgmt/ec_host_cmd/backends/CMakeLists.txt

@@ -21,3 +21,7 @@ zephyr_library_sources_ifdef(
 zephyr_library_sources_ifdef(
 	CONFIG_EC_HOST_CMD_BACKEND_UART
 	ec_host_cmd_backend_uart.c)
+
+zephyr_library_sources_ifdef(
+	CONFIG_EC_HOST_CMD_BACKEND_SPI_STM32
+	ec_host_cmd_backend_spi_stm32.c)

subsys/mgmt/ec_host_cmd/backends/Kconfig

@@ -6,6 +6,7 @@
 DT_CHOSEN_ESPI_BACKEND := zephyr,host-cmd-espi-backend
 DT_CHOSEN_SHI_BACKEND := zephyr,host-cmd-shi-backend
 DT_CHOSEN_UART_BACKEND := zephyr,host-cmd-uart-backend
+DT_CHOSEN_SPI_BACKEND := zephyr,host-cmd-spi-backend
 
 config EC_HOST_CMD_BACKEND_SIMULATOR
 	bool "Embedded Controller Host Command Backend Simulator"
@@ -37,6 +38,12 @@ config EC_HOST_CMD_BACKEND_UART
 	  Enable support for Embedded Controller host commands using
 	  the UART.
 
+config EC_HOST_CMD_BACKEND_SPI
+	bool "Host commands support using SPI"
+	help
+	  Enable support for Embedded Controller host commands using
+	  the SPI.
+
 if EC_HOST_CMD_BACKEND_SHI
 
 choice EC_HOST_CMD_BACKEND_SHI_DRIVER
@@ -79,3 +86,19 @@ config EC_HOST_CMD_BACKEND_SHI_MAX_RESPONSE
 	  response.
 
 endif # EC_HOST_CMD_BACKEND_SHI
+
+if EC_HOST_CMD_BACKEND_SPI
+
+choice EC_HOST_CMD_BACKEND_SPI_DRIVER
+	prompt "SHI driver"
+	default EC_HOST_CMD_BACKEND_SPI_STM32 if SOC_FAMILY_STM32
+
+config EC_HOST_CMD_BACKEND_SPI_STM32
+	bool "SPI by STM32"
+	help
+	  This option enables the driver for SPI backend in the
+	  STM32 chip family.
+
+endchoice
+
+endif # EC_HOST_CMD_BACKEND_SPI