如何在Linux上调试无法绑定到设备的驱动程序？

我试图弄清楚为什么我的Creator CI20上的驱动程序未安装以下设备。供参考，我使用Linux内核v4.13.0并在本地进行编译：

make ARCH=mips ci20_defconfig
make -j8 ARCH=mips CROSS_COMPILE=mipsel-linux-gnu- uImage

从正在运行的系统中，我可以看到：

ci20@ci20:~# find /sys | grep rng
/sys/firmware/devicetree/base/jz4780-cgu@10000000/rng@d8
/sys/firmware/devicetree/base/jz4780-cgu@10000000/rng@d8/compatible
/sys/firmware/devicetree/base/jz4780-cgu@10000000/rng@d8/name
/sys/bus/platform/drivers/jz4780-rng
/sys/bus/platform/drivers/jz4780-rng/bind
/sys/bus/platform/drivers/jz4780-rng/unbind
/sys/bus/platform/drivers/jz4780-rng/uevent

因此内核在运行时可以看到该设备，现在缺少的部分是为什么驱动程序从未绑定？我本来期望这样的事情：

/sys/bus/platform/drivers/jz4780-rng/100000d8.rng

我确实找到了其他一些文章来解释如何调试正在运行的系统，例如：

• /programming/28406776/driver-binding-using-device-tree-without-compatible-string-in-the-driver
• /programming/35580862/device-tree-mismatch-probe-never-所谓
• /programming/41446737/platform-device-driver-autoloading-mechanism
• 是否可以使用正在运行的内核的/ sys获取设备树的信息？

尽管这些帖子的信息准确无误，但对我来说却不是很有帮助。由于我是在本地构建内核（我printk在jz4780-rng驱动程序的probe函数中添加了），所以我的问题是：

• 我应该在编译时打开什么选项，以便内核在无法调用jz4780-rng驱动程序的probe函数时输出准确的信息？
• 特别是我该如何打印经过测试的总线/驱动器的完整列表driver_probe_device？

我printk可以在代码中的任何地方添加调试它。问题在于：哪个函数正在遍历设备树并调用probe / init函数？

以供参考：

$ dtc -I fs -O dts /sys/firmware/devicetree/base | grep -A 1 rng
              rng@d8 {
                      compatible = "ingenic,jz4780-rng";
              };

兼容字符串声明为：

cgu: jz4780-cgu@10000000 {
    compatible = "ingenic,jz4780-cgu", "syscon";
    reg = <0x10000000 0x100>;

    clocks = <&ext>, <&rtc>;
    clock-names = "ext", "rtc";

    #clock-cells = <1>;

    rng: rng@d8 {
        compatible = "ingenic,jz4780-rng";
    };
};

并在驱动程序中为：

static const struct of_device_id jz4780_rng_dt_match[] = {
    {
        .compatible = "ingenic,jz4780-rng",
    },
    { },
};
MODULE_DEVICE_TABLE(of, jz4780_rng_dt_match);

static struct platform_driver jz4780_rng_driver = {
    .driver     = {
        .name   = "jz4780-rng",
        .of_match_table = jz4780_rng_dt_match,
    },
    .probe      = jz4780_rng_probe,
    .remove     = jz4780_rng_remove,
};
module_platform_driver(jz4780_rng_driver);

更新1：

当我使用构建内核时CONFIG_DEBUG_DRIVER=y，可以看到以下内容：

# grep driver_probe_device syslog
Sep  6 10:08:07 ci20 kernel: [    0.098280] bus: 'platform': driver_probe_device: matched device 10031000.serial with driver ingenic-uart
Sep  6 10:08:07 ci20 kernel: [    0.098742] bus: 'platform': driver_probe_device: matched device 10033000.serial with driver ingenic-uart
Sep  6 10:08:07 ci20 kernel: [    0.099209] bus: 'platform': driver_probe_device: matched device 10034000.serial with driver ingenic-uart
Sep  6 10:08:07 ci20 kernel: [    0.106945] bus: 'platform': driver_probe_device: matched device 1b000000.nand-controller with driver jz4780-nand
Sep  6 10:08:07 ci20 kernel: [    0.107282] bus: 'platform': driver_probe_device: matched device 134d0000.bch with driver jz4780-bch
Sep  6 10:08:07 ci20 kernel: [    0.107470] bus: 'platform': driver_probe_device: matched device 16000000.dm9000 with driver dm9000
Sep  6 10:08:07 ci20 kernel: [    0.165618] bus: 'platform': driver_probe_device: matched device 10003000.rtc with driver jz4740-rtc
Sep  6 10:08:07 ci20 kernel: [    0.166177] bus: 'platform': driver_probe_device: matched device 10002000.jz4780-watchdog with driver jz4740-wdt
Sep  6 10:08:07 ci20 kernel: [    0.170930] bus: 'platform': driver_probe_device: matched device 1b000000.nand-controller with driver jz4780-nand

但是只有：

# grep rng syslog
Sep  6 10:08:07 ci20 kernel: [    0.166842] bus: 'platform': add driver jz4780-rng
Sep  6 10:08:42 ci20 kernel: [   54.584451] random: crng init done

附带说明一下，此处未引用rng顶级节点：cgu，但有一个jz4780-cgu驱动程序。

更新2：

如果将rng节点声明移到顶级cgu节点之外，至少可以看到最后发生了一些绑定：

# grep rng /var/log/syslog 
Sep  6 10:30:57 ci20 kernel: [    0.167017] bus: 'platform': add driver jz4780-rng
Sep  6 10:30:57 ci20 kernel: [    0.167033] bus: 'platform': driver_probe_device: matched device 10000000.rng with driver jz4780-rng
Sep  6 10:30:57 ci20 kernel: [    0.167038] bus: 'platform': really_probe: probing driver jz4780-rng with device 10000000.rng
Sep  6 10:30:57 ci20 kernel: [    0.167050] jz4780-rng 10000000.rng: no pinctrl handle
Sep  6 10:30:57 ci20 kernel: [    0.167066] devices_kset: Moving 10000000.rng to end of list
Sep  6 10:30:57 ci20 kernel: [    0.172774] jz4780-rng: probe of 10000000.rng failed with error -22
Sep  6 10:31:32 ci20 kernel: [   54.802794] random: crng init done

使用：

    rng: rng@100000d8 {
        compatible = "ingenic,jz4780-rng";
    };

我还可以验证：

# find /sys/ | grep rng
/sys/devices/platform/10000000.rng
/sys/devices/platform/10000000.rng/subsystem
/sys/devices/platform/10000000.rng/driver_override
/sys/devices/platform/10000000.rng/modalias
/sys/devices/platform/10000000.rng/uevent
/sys/devices/platform/10000000.rng/of_node
/sys/firmware/devicetree/base/rng@100000d8
/sys/firmware/devicetree/base/rng@100000d8/compatible
/sys/firmware/devicetree/base/rng@100000d8/status
/sys/firmware/devicetree/base/rng@100000d8/reg
/sys/firmware/devicetree/base/rng@100000d8/name
/sys/bus/platform/devices/10000000.rng
/sys/bus/platform/drivers/jz4780-rng
/sys/bus/platform/drivers/jz4780-rng/bind
/sys/bus/platform/drivers/jz4780-rng/unbind
/sys/bus/platform/drivers/jz4780-rng/uevent

使驱动程序绑定到设备的可行解决方案是：

cgublock: jz4780-cgublock@10000000 {
    compatible = "simple-bus", "syscon";

    #address-cells = <1>;
    #size-cells = <1>;

    reg = <0x10000000 0x100>;
    ranges;

    cgu: jz4780-cgu@10000000 {
        compatible = "ingenic,jz4780-cgu";
        reg = <0x10000000 0x100>;

        clocks = <&ext>, <&rtc>;
        clock-names = "ext", "rtc";

        #clock-cells = <1>;
    };

    rng: rng@d8 {
        compatible = "ingenic,jz4780-rng";
        reg = <0x100000d8 0x8>;
    };
};

盯着其他例子可以发现这一点。我希望能得到正确诊断的解决方案，以便能正确解释为什么先前的尝试不正确。