TIM device tree configuration

Article purpose

本文的目的是解释'在将外围设备分配给 Linux^® OS，如何配置“Timer(Tim)” ':

• 配置定时器peripheral以启用PWM，触发或正交编码器。
• 配置board，例如 TIM引脚。

使用设备树机制执行配置。

TIM Linux driver 使用它在PWM 和 IIO 框架中注册相关信息。

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

“ TIM内部外围设备” 是多功能设备（MFD）。

每个功能由单独的DT绑定文档表示：

• STM32 TIM MFD设备树绑定 文档涉及核心资源（例如寄存器，时钟，DMA）

• STM32 TIM PWM设备树绑定 文档涉及PWM资源（例如PWM输入/输出引脚）
• STM32 TIM IIO触发器/编码器设备树绑定文档涉及其他内部外设触发和正交编码器资源

DT configuration

该硬件描述是STM32微处理器和电路板设备树文件的组合。 有关设备树文件分割的更多说明，请参见Device tree. STM32CubeMX可用于生成板卡设备树。 请参阅[[#How_to_configure_the_DT_using _STM32CubeMX|How to configure the DT using STM32CubeMX]].

DT configuration (STM32 level)

TIM节点在stm32mp157c.dtsi .

DT根节点（例如timers1 ...）和DT子节点描述了TIM features ，例如：

• 触发和正交编码器

它们还描述了硬件参数，例如寄存器地址，时钟和DMA。

timers1: timer@address {
	/* timer common resources */
	compatible = "st,stm32-timers";
	...
	pwm {
		/* PWM*/
		compatible = "st,stm32-pwm";
	};
	timer@0 {
		/* trigger and quadrature encoder */
		compatible = "st,stm32h7-timer-trigger";
		/* trigger identifier (e.g. 0 for TIM1 triggers, 1 for TIM2... */
		reg = <0>;
	};
};

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)

该部分用于配置和启用板上使用的TIM硬件

• 通过设置为正在使用的TIM实例（例如timers1 ...）启用'DT根节点'status = "okay";
• 通过设置 status = "okay"'''为使用中的功能（PWM输入/输出，触发和正交编码器）启用'''DT子节点'''。;
• 通过pinctrl 到 pinctrl-0, pinctrl-1 和pinctrl-names.

要在板上启用PWM捕获（可选），必须配置DMA：

• 通过设置dmas = <...>, <...>; 启用与PWM输入对应的DMA通道 匹配 dma-names = "ch1", "ch3";.

When PWM capture isn't used, it's recommended to disable DMA channels by default, to spare them for other usage:

• Disable DMA channels by setting /delete-property/dmas and /delete-property/dma-names

DT configuration examples

TIM configured in PWM mode

下面的示例显示了如何配置TIM1通道1作为：

• PE9上的PWM输出，例如 TIM1_CH1(See pinctrl device tree configuration and GPIO internal peripheral)
• PWM device tree provider (e.g. TIM1_CH1) used by a device tree consumer (e.g. like "pwm-leds"). This is available since ecosystem release ≥ v1.1.0{{#set:Ecosystem release=revision of a previous flow 1.1.0}}

/* select TIM1_CH1 alternate function 1 on 'PE9' */
pwm1_pins_a: pwm1-0 {
	pins {
		pinmux = <STM32_PINMUX('E', 9, AF1)>;
		bias-pull-down;
		drive-push-pull;
		slew-rate = <0>;
	};
};

/* configure 'PE9' as analog input in low-power mode */
pwm1_sleep_pins_a: pwm1-sleep-0 {
	pins {
		pinmux = <STM32_PINMUX('E', 9, ANALOG)>;
	};
};

The PWM output doesn't require any DMA channel. Disable them if they are configured by default in the .dtsi file.

/* PWM DT provider on TIM1: "pwm1" */
&timers1 {
	status = "okay";
	/* spare all DMA channels since they are not needed for PWM output */
	/delete-property/dmas;
	/delete-property/dma-names;
	/* define pwm1 label */
	pwm1: pwm {
		/* configure PWM pins on TIM1_CH1 */
		pinctrl-0 = <&pwm1_pins_a>;
		pinctrl-1 = <&pwm1_sleep_pins_a>;
		pinctrl-names = "default", "sleep";
		/* enable PWM on TIM1 */
		status = "okay";
	};
};

PWM DT user example below is available since ecosystem release ≥ v1.1.0{{#set:Ecosystem release=revision of a previous flow 1.1.0}}

The TIM PWM DT user specifier encodes 3 cells: PWM number (0 for CH1, 1 for CH2 and so on) PWM period in nanoseconds PWM polarity (0 for normal polarity or PWM_POLARITY_INVERTED)

/ {
	...
	/* PWM DT user on TIM1_CH1: "pwm1", example with "pwm-leds" */
	pwmleds {
		compatible = "pwm-leds";
		example {
			label = "stm32-pwm-leds-example";
			/* Use pwm1 channel 0 (e.g. TIM1_CH1) */
			/* period in nanoseconds (500000), normal polarity (0) */
			pwms = <&pwm1 0 500000 0>;
			max-brightness = <127>;
		};
	};
};

TIM configured in PWM mode and trigger source

The example below shows how to configure TIM1 channel 1 to act as:

• PWM output on PE9, e.g. TIM1_CH1 (See pinctrl device tree configuration and GPIO internal peripheral)
• trigger source (synchronous with PWM) for other internal peripheral such as STM32 ADC

/* select TIM1_CH1 alternate function 1 on 'PE9' */
pwm1_pins_a: pwm1-0 {
	pins {
		pinmux = <STM32_PINMUX('E', 9, AF1)>;
		bias-pull-down;
		drive-push-pull;
		slew-rate = <0>;
	};
};

/* configure 'PE9' as analog input in low-power mode */
pwm1_sleep_pins_a: pwm1-sleep-0 {
	pins {
		pinmux = <STM32_PINMUX('E', 9, ANALOG)>;
	};
};

The PWM output doesn't require any DMA channel. Disable them if they are configured by default in the .dtsi file.

&timers1 {
	status = "okay";
	/* spare all DMA channels since they are not needed for PWM output */
	/delete-property/dmas;
	/delete-property/dma-names;
	pwm {
		/* configure PWM on TIM1_CH1 */
		pinctrl-0 = <&pwm1_pins_a>;          
		pinctrl-1 = <&pwm1_sleep_pins_a>;
		pinctrl-names = "default", "sleep";
		/* enable PWM on TIM1 */
		status = "okay";
	};
	timer@0 {
		/* enable trigger on TIM1 */
		status = "okay";
	};
};

TIM configured in PWM input capture mode

The example below shows how to configure TIM1 channel 1 in PWM input capture mode (e.g. period and duty cycle):

• Configure PWM input on PE9, e.g. TIM1_CH1 (See pinctrl device tree configuration and GPIO internal peripheral)

/* select TIM1_CH1 alternate function 1 on 'PE9' */
pwm1_in_pins_a: pwm1-in-0 {
	pins {
		pinmux = <STM32_PINMUX('E', 9, AF1)>;
		bias-disable;
	};
};

/* configure 'PE9' as analog input in low-power mode */
pwm1_in_sleep_pins_a: pwm1-in-sleep-0 {
	pins {
		pinmux = <STM32_PINMUX('E', 9, ANALOG)>;
	};
};

A DMA channel is required and must be configured depending on the PWM input channel:

• Select DMA channel 1, "ch1", to capture PWM input channel 1 and/or 2
• Select DMA channel 3, "ch3", to capture PWM input channel 3 and/or 4
• Select both "ch1" and "ch3" dmas to enable capture on all PWM input channels

&timers1 {
	status = "okay";
	/* Enable DMA "ch1" for PWM input on TIM1_CH1 */
	dmas = <&dmamux1 11 0x400 0x5>;
	dma-names = "ch1";
	pwm {
		/* configure PWM input pins, e.g. TIM1_CH1 */
		pinctrl-0 = <&pwm1_in_pins_a>;
		pinctrl-1 = <&pwm1_in_sleep_pins_a>;
		pinctrl-names = "default", "sleep";
		/* enable PWM on TIM1 */
		status = "okay";
	};
};

DMA channels 1 and/or 3 for each TIM can be picked from the "dmas" list in stm32mp157c.dtsi file

TIM configured as quadrature encoder interface

The example below shows how to configure TIM1 to interface with a quadrature encoder:

• Configure PE9 and PJ11 as encoder input pins, e.g. TIM1_CH1, TIM1_CH2 (see pinctrl device tree configuration and GPIO internal peripheral)

tim1_in_pins_a: tim1-in-pins-0 {
	pins {
		pinmux = <STM32_PINMUX('E', 9, AF1)>, /* TIM1_CH1 */
			 <STM32_PINMUX('J', 11, AF1)>; /* TIM1_CH2 */
		bias-disable;
	};
};

tim1_in_pins_sleep_a: tim1-in-pins-sleep-0 {
	pins {
		pinmux = <STM32_PINMUX('E', 9, ANALOG)>, /* TIM1_CH1 */
			 <STM32_PINMUX('J', 11, ANALOG)>; /* TIM1_CH2 */
	};
};

&timers1 {
	status = "okay";
	/delete-property/dmas;                       /* spare all DMA channels since they are not required for quadrature encoder interface */
	/delete-property/dma-names;
	timer@0 {
		pinctrl-0 = <&tim1_in_pins_a>;       /* configure TIM1_CH1 and TIM1_CH2 as encoder input pins */
		pinctrl-1 = <&tim1_in_pins_sleep_a>;
		pinctrl-names = "default", "sleep";
		status = "okay";                     /* enable Encoder interface mode on TIM1 */
	};
};

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: