FDCAN device tree configuration

Article purpose

本文介绍了如何配置FDCAN when it is assigned to the Linux^® 操作系统。 在这种情况下，它由 CAN framework 用于Bosch M_CAN控制器。

使用 device tree机制执行配置，该机制提供了FDCAN外设的硬件描述，并由M_CAN Linux驱动程序和 NET/CAN 框架使用。

如果外围设备已分配给另一个执行上下文，请参阅How to assign an internal peripheral to a runtime context 文章，以获取有关外围设备分配和配置的准则。

DT bindings documentation

M_CAN设备树绑定 描述了所有必需和可选属性。

DT configuration

该硬件描述是 STM32 microprocessor 设备树文件（扩展名为.dtsi）和“板子”设备树文件（扩展名为.dts）的组合。 有关设备树文件分割的说明，请参见Device tree。

STM32CubeMX 可用于生成板卡设备树。有关更多详细信息，请参考How to configure the DT using STM32CubeMX。

DT configuration (STM32 level)

所有M_CAN节点均在stm32mp157c.dtsi中进行了描述 文件，该文件具有禁用状态和必需的属性，例如：

• 物理基址和设备寄存器映射的大小
• 消息RAM地址和大小（CAN SRAM）
• 主机时钟和CAN时钟
• 消息RAM配置

这是一组属性，对于给定的STM32器件可能不会改变。

 m_can1: can@4400e000 {
 	compatible = "bosch,m_can";                       
 	reg = <0x4400e000 0x400>, <0x44011000 0x1400>;    /* FDCAN1 uses only the first half of the dedicated CAN_SRAM */
 	reg-names = "m_can", "message_ram";
 	interrupts = <GIC_SPI 19 IRQ_TYPE_LEVEL_HIGH>,
 		     <GIC_SPI 21 IRQ_TYPE_LEVEL_HIGH>;
 	interrupt-names = "int0", "int1";
 	clocks = <&rcc CK_HSE>, <&rcc FDCAN_K>;
 	clock-names = "hclk", "cclk";
 	bosch,mram-cfg = <0x0 0 0 32 0 0 2 2>;
 	status = "disabled";
 };
 
 m_can2: can@4400f000 {
 	compatible = "bosch,m_can";
 	reg = <0x4400f000 0x400>, <0x44011000 0x2800>;    /* The 10 Kbytes of the CAN_SRAM are mapped */
 	reg-names = "m_can", "message_ram";
 	interrupts = <GIC_SPI 20 IRQ_TYPE_LEVEL_HIGH>,
 		     <GIC_SPI 22 IRQ_TYPE_LEVEL_HIGH>;
 	interrupt-names = "int0", "int1";
 	clocks = <&rcc CK_HSE>, <&rcc FDCAN_K>;
 	clock-names = "hclk", "cclk";
 	bosch,mram-cfg = <0x1400 0 0 32 0 0 2 2>;         /* Set mram-cfg offset to write FDCAN2 data on the second half of the dedicated CAN_SRAM */
 	status = "disabled";
 };

bindings files中完整描述了必需和可选的属性。

该设备树部分与STM32微处理器有关。它必须保持原样，而不能由最终用户修改。

DT configuration (board level)

device tree 的一部分用于描述在给定板上使用的FDCAN硬件。 DT节点 ("m_can") 必须填写：

• 通过设置 status = "okay".来启用CAN块。
• 通过 pinctrl, through pinctrl-0 (default pins), pinctrl-1 (sleep pins) and pinctrl-names来配置正在使用的管脚。

DT configuration examples

以下示例显示了如何在板级上配置和启用FDCAN1实例：

 &m_can1 {
 	pinctrl-names = "default", "sleep";         /* configure pinctrl modes for m_can1 */
 	pinctrl-0 = <&m_can1_pins_a>;               /* configure m_can1_pins_a as default pinctrl configuration for m_can1 */
 	pinctrl-1 = <&m_can1_sleep_pins_a>;         /* configure m_can1_sleep_pins_a as sleep pinctrl configuration for m_can1 */
 	status = "okay";                            /* enable m_can1 */ 
 };

How to configure the DT using STM32CubeMX

The STM32CubeMX tool can be used to configure the STM32MPU device and get the corresponding platform configuration device tree files.
The STM32CubeMX may not support all the properties described in the above DT bindings documentation paragraph. If so, the tool inserts user sections in the generated device tree. These sections can then be edited to add some properties and they are preserved from one generation to another. Refer to STM32CubeMX user manual for further information.

References

Please refer to the following links for additional information: