IMX8MM平台SNVS子模块内核驱动probe函数未调用排查求助

问题描述 #

为IMX8MM处理器编写调用SNVS模块的简易内核驱动，参考内核rtc-snvs.c实现，但新增的snvs_mc驱动的probe函数始终未触发。已在imx8mm.dtsi中添加snvs_mc节点，相关代码如下：

原设备树片段 #

snvs: snvs@30370000 {
    compatible = "fsl,sec-v4.0-mon","syscon", "simple-mfd";
    reg = <0x30370000 0x10000>;

    snvs_rtc: snvs-rtc-lp {
       compatible = "fsl,sec-v4.0-mon-rtc-lp";
       regmap = <&snvs>;
       offset = <0x34>;
       interrupts = <GIC_SPI 19 IRQ_TYPE_LEVEL_HIGH>,
               <GIC_SPI 20 IRQ_TYPE_LEVEL_HIGH>;
       clocks = <&clk IMX8MM_CLK_SNVS_ROOT>;
       clock-names = "snvs-rtc";
    };

    snvs_pwrkey: snvs-powerkey {
       compatible = "fsl,sec-v4.0-pwrkey";
       regmap = <&snvs>;
       interrupts = <GIC_SPI 4 IRQ_TYPE_LEVEL_HIGH>;
       clocks = <&clk IMX8MM_CLK_SNVS_ROOT>;
       clock-names = "snvs-pwrkey";
       linux,keycode = <KEY_POWER>;
       wakeup-source;
       status = "disabled";
    };
 };

修改后的设备树片段 #

snvs: snvs@30370000 {
    compatible = "fsl,sec-v4.0-mon","syscon", "simple-mfd";
    reg = <0x30370000 0x10000>;

    snvs_mc: snvs-mc-lp {
       compatible = "fsl,sec-v4.0-mc-lp";
       regmap = <&snvs>;
    };

    snvs_rtc: snvs-rtc-lp {
       compatible = "fsl,sec-v4.0-mon-rtc-lp";
       regmap = <&snvs>;
       offset = <0x34>;
       interrupts = <GIC_SPI 19 IRQ_TYPE_LEVEL_HIGH>,
               <GIC_SPI 20 IRQ_TYPE_LEVEL_HIGH>;
       clocks = <&clk IMX8MM_CLK_SNVS_ROOT>;
       clock-names = "snvs-rtc";
    };

    snvs_pwrkey: snvs-powerkey {
       compatible = "fsl,sec-v4.0-pwrkey";
       regmap = <&snvs>;
       interrupts = <GIC_SPI 4 IRQ_TYPE_LEVEL_HIGH>;
       clocks = <&clk IMX8MM_CLK_SNVS_ROOT>;
       clock-names = "snvs-pwrkey";
       linux,keycode = <KEY_POWER>;
       wakeup-source;
       status = "disabled";
    };
 };

自定义驱动框架代码 #

static const struct of_device_id snvs_mc_ids[] = {
        { .compatible = "fsl,sec-v4.0-mc-lp", },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, snvs_mc_ids);

static struct platform_driver snvs_mc_driver = {
        .driver = {
                .name = "snvs_mc",
                .pm   = &snvs_mc_pm_ops,
                .of_match_table = snvs_mc_ids,
        },
        .probe      = snvs_mc_probe,
};

module_platform_driver(snvs_mc_driver);
MODULE_LICENSE("GPL");

参考的内核rtc-snvs.c代码片段 #

static const struct of_device_id snvs_dt_ids[] = {
   { .compatible = "fsl,sec-v4.0-mon-rtc-lp", }, 
   { /* sentinel */ } 
};
MODULE_DEVICE_TABLE(of, snvs_dt_ids);

static struct platform_driver snvs_rtc_driver = {
   .driver = {
      .name = "snvs_rtc",
      .pm   = &snvs_rtc_pm_ops,
      .of_match_table = snvs_dt_ids,
   },
   .probe      = snvs_rtc_probe,
};
module_platform_driver(snvs_rtc_driver);

MODULE_AUTHOR("Freescale Semiconductor, Inc.");
MODULE_DESCRIPTION("Freescale SNVS RTC Driver");
MODULE_LICENSE("GPL");

排查要点 #

• 验证MFD子节点的兼容性匹配
  父节点snvs属于*MFD（Multi-Function Device）*框架，会遍历子节点创建设备。先通过命令确认设备树节点是否正确加载：

  cat /proc/device-tree/snvs@30370000/snvs-mc-lp/compatible
  

  确保输出的字符串和驱动中of_match_table里的"fsl,sec-v4.0-mc-lp"完全一致，无拼写、大小写或空格差异。

• 确认驱动的编译与加载状态

  1. 若驱动编译进内核，检查内核配置是否开启对应选项（如CONFIG_SNVS_MC=y）；
  2. 若作为模块，执行lsmod | grep snvs_mc确认模块是否加载，未加载则手动加载并查看日志：

     insmod snvs_mc.ko
     dmesg | tail -20
     

     查看是否有驱动注册失败、兼容性不匹配的报错信息。

• 检查MFD子节点的必要属性
  参考snvs_rtc节点，它包含时钟、偏移量等属性，而你的snvs_mc节点仅配置了regmap。部分MFD子驱动需要额外属性才能被框架识别，尝试添加时钟属性并更新驱动：
  修改设备树节点：

  snvs_mc: snvs-mc-lp {
      compatible = "fsl,sec-v4.0-mc-lp";
      regmap = <&snvs>;
      clocks = <&clk IMX8MM_CLK_SNVS_ROOT>;
      clock-names = "snvs-mc";
  };
  

  驱动中添加时钟获取逻辑（参考rtc-snvs.c的时钟处理）。

• 查看内核MFD框架日志
  过滤内核日志中的MFD相关信息，查看是否有节点处理错误：

  dmesg | grep -i mfd
  dmesg | grep snvs
  

  重点关注是否有snvs-mc-lp节点被跳过、属性缺失或兼容性不匹配的提示。

• 排查驱动注册的潜在问题
  若snvs_mc_pm_ops未正确定义，可能导致驱动注册失败。暂时注释掉.pm字段测试：

  static struct platform_driver snvs_mc_driver = {
          .driver = {
                  .name = "snvs_mc",
                  // .pm   = &snvs_mc_pm_ops,
                  .of_match_table = snvs_mc_ids,
          },
          .probe      = snvs_mc_probe,
  };
  

内容的提问来源于stack exchange，提问作者OfficeMan