PWM 配置

内核配置

在 SDK 根目录下，执行下列命令，进入 kernel 的功能配置界面：
```
make kernel-menuconfig
```
或使用简写命令
```
make km
```

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

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。

在 SDK 根目录下执行 make kernel-menuconfig 或 make me，进入 kernel 的功能配置，按如下选择：

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

如使用 logo 功能，须在 Boot 阶段打开屏幕背光，否则可跳过。

在 SDK 根目录下执行 make kernel-menuconfig 或 make me，进入 kernel 的功能配置，按如下选择：

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

时钟配置

PWM 模块涉及时钟的衍生关系：

EWM 模块涉及时钟的衍生关系：

其中，前两个时钟在 PWM 控制器的节点中配置，后两个时钟在 Board 中的 PWM 子节点（对应通道）中配置。

注：

容易混淆的 sysclk：

PWM 驱动中，按照惯例将父时钟称作 sysclk，即上图的 PLL INT1。
PWM 硬件 spec 中，将上图中的 PWM Clk 称作 sysclk。

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";
    ...
};