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PWM 配置

3 Mar 2025
Read time: 7 minute(s)

内核配置

  2. 在内核配置界面，按如下选择：
    Linux
    Device Drivers  --->
        [*] Pulse-Width Modulation (PWM) Support  --->
            <*>   ArtInChip PWM support
            <*>   ArtInChip EPWM support

  3. 如需设置 PWM 模块的背光控制功能，执行下列配置，否则可跳过。

    Linux
    Device Drivers  --->
        Graphics support  --->
            Backlight & LCD device support  --->
                <*> Lowlevel Backlight controls
                <*>   Generic PWM based Backlight Driver

  4. 如使用 logo 功能，须在 Boot 阶段打开屏幕背光，否则可跳过。

    U-Boot
    Device Drivers  --->
        [*] Enable support for pulse-width modulation devices (PWM)
        [*]   Enable support for ArtInChip PWM
        Graphics support  --->
            [*] Generic PWM based Backlight Driver

DTS 参数配置

PWM 驱动支持从 DTS 中配置的自定义参数，如下表所示：

表 1. PWM 自定义参数

参数名称

类型

取值范围

功能说明

mode

String

up/down/up-down-count

配置增减模式

tb-clk-rate

Integer

(0, 24000000)

时基计数器的工作时钟

action0

String

none/low/high/inverse

多个关键时点的触发行为

action1

String

none/low/high/inverse

多个关键时点的触发行为

default-level

Integer

[0, 1]

默认/初始电平
注：

为了方便表达，所有参数名称都省略了前缀 “aic,”。

表中 action0 和 action1 四种取值的含义，定义如下：

表 2. action0 和 action1 取值含义

Action 类型

行为描述

none

不做任何变化，保持之前的输出电平

low

跳变为 0 电平

high

跳变为 1 电平

inverse

跳变为反向的电平，比如从 0 跳变为 1

D211 配置

common/d211.dtsi 中的参数配置：

pwm: pwm@19240000 {
    compatible = "artinchip,aic-pwm-v1.0";
    reg = <0x0 0x19240000 0x0 0x1000>;
    interrupts-extended = <&plic0 90 IRQ_TYPE_LEVEL_HIGH>;
    #pwm-cells = <3>;
    clocks = <&cmu CLK_PWM>, <&cmu CLK_PLL_INT1>;
    clock-names = "pwm", "sysclk";
    resets = <&rst RESET_PWM>;
    clock-rate = <48000000>;
};

epwm: epwm@18200000 {
    compatible = "artinchip,aic-epwm-v1.0";
    reg = <0x0 0x18200000 0x0 0x600>, <0 0x1820F000 0x0 0x1000>;
    interrupts-extended = <&plic0 25 IRQ_TYPE_LEVEL_HIGH>;
    #pwm-cells = <3>;
    clocks = <&cmu CLK_PWMCS>, <&cmu CLK_PLL_INT1>;
    clock-names = "pwmcs", "sysclk";
    resets = <&rst RESET_PWMCS>;
    clock-rate = <48000000>;
    status = "disabled";
};

Board 配置

  • PWM 通道配置
    xxx/board.dts 中的参数配置：
    &pwm {
    status = "okay";
    pinctrl-names = "default";
    pinctrl-0 = <&pwm2_pins_b>;
    /* mode: up-count, down-count, up-down-count
       action: none, low, high, inverse */
    pwm0 {
        aic,mode = "up-count";
        aic,tb-clk-rate = <24000000>;
        aic,rise-edge-delay = <10>;
        aic,fall-edge-delay = <10>;
        /*            CBD,    CBU,    CAD,    CAU,    PRD,   ZRO */
        aic,action0 = "none", "none", "none", "low", "none", "high";
        aic,action1 = "none", "none", "none", "high", "none", "low";
        status = "disabled";
    };

    pwm1 {
        aic,mode = "down-count";
        aic,tb-clk-rate = <24000000>;
        aic,rise-edge-delay = <10>;
        aic,fall-edge-delay = <10>;
        /*            CBD,    CBU,    CAD,    CAU,    PRD,   ZRO */
        aic,action0 = "none", "none", "none", "low", "none", "high";
        aic,action1 = "none", "none", "none", "high", "none", "low";
        status = "disabled";
    };

    pwm2 {
        aic,mode = "up-count";
        aic,tb-clk-rate = <24000000>;
        /*            CBD,    CBU,    CAD,    CAU,    PRD,   ZRO */
        aic,action0 = "none", "none", "none", "high", "low", "none";
        aic,action1 = "none", "none", "none", "low", "high", "none";
        aic,default-level = <0>;
        aic,rise-edge-delay = <10>;
        aic,fall-edge-delay = <10>;
        status = "okay";
    };

    pwm3 {
        aic,mode = "up-count";
        aic,tb-clk-rate = <24000000>;
        /*            CBD,    CBU,    CAD,    CAU,    PRD,   ZRO */
        aic,action0 = "none", "none", "none", "low", "high", "none";
        aic,action1 = "none", "none", "none", "high", "low", "none";
        aic,rise-edge-delay = <10>;
        aic,fall-edge-delay = <10>;
        status = "disabled";
    };
};

&epwm {
    status = "disabled";
    pinctrl-names = "default";
    pinctrl-0 = <&epwm0_pins_a>,
             <&epwm1_pins_a>,
             <&epwm2_pins_a>;
    /* mode: up-count, down-count, up-down-count
    action: none, low, high, inverse */
    epwm0 {
        aic,mode = "up-count";
        aic,tb-clk-rate = <24000000>;
        /*            CBD,    CBU,    CAD,    CAU,    PRD,   ZRO */
        aic,action0 = "none", "none", "none", "high", "none", "low";
        aic,action1 = "none", "high", "none", "none", "none", "low";
        status = "disabled";
    };

    epwm1 {
        aic,mode = "up-count";
        aic,tb-clk-rate = <24000000>;
        /*            CBD,    CBU,    CAD,    CAU,    PRD,   ZRO */
        aic,action0 = "none", "none", "none", "high", "none", "low";
        aic,action1 = "none", "high", "none", "none", "none", "low";
        status = "disabled";
    };

    epwm2 {
        aic,mode = "up-count";
        aic,tb-clk-rate = <24000000>;
        /*            CBD,    CBU,    CAD,    CAU,    PRD,   ZRO */
        aic,action0 = "none", "none", "none", "high", "none", "low";
        aic,action1 = "none", "high", "none", "none", "none", "low";
        status = "disabled";
    };

    epwm3 {
        aic,mode = "up-count";
        aic,tb-clk-rate = <24000000>;
        /*            CBD,    CBU,    CAD,    CAU,    PRD,   ZRO */
        aic,action0 = "none", "none", "none", "high", "none", "low";
        aic,action1 = "none", "high", "none", "none", "none", "low";
        status = "disabled";
    };

    epwm4 {
        aic,mode = "up-count";
        aic,tb-clk-rate = <24000000>;
        /*            CBD,    CBU,    CAD,    CAU,    PRD,   ZRO */
        aic,action0 = "none", "none", "none", "high", "none", "low";
        aic,action1 = "none", "high", "none", "none", "none", "low";
        status = "disabled";
    };

    epwm5 {
        aic,mode = "up-count";
        aic,tb-clk-rate = <24000000>;
        /*            CBD,    CBU,    CAD,    CAU,    PRD,   ZRO */
        aic,action0 = "none", "none", "none", "high", "none", "low";
        aic,action1 = "none", "high", "none", "none", "none", "low";
        status = "disabled";
    };
};
  • 背光控制配置
    需要在 xxx/board.dts 中新增一个 backlight 节点，如下：
    backlight: backlight {
    compatible = "pwm-backlight";
    /* pwm node name; pwm device No.; period_ns; pwm_polarity */
    pwms = <&pwm 2 1000000 0>;
    brightness-levels = <0 10 20 30 40 50 60 70 80 90 100>;
    default-brightness-level = <8>;
    status = "okay";
};

    其中 “&pwm 2” 表示要使用 pwm2 通道作为背光控制用（要确认和硬件上的电路连接是一致的）。

    在屏幕 panel 节点中，需要引用 backlight：
    panel_lvds {
    compatible = "artinchip,aic-general-lvds-panel";
    data-mapping = "vesa-24";
    data-channel = "single-link1";
    backlight = <&backlight>;
    status = "okay";
    ...
};