Help, please, with getting a custom I2C real time clock module to load

[Lee D]

Hi Everyone,

I have written a new I2C driver (for the Xilinx Zynq) and a new real
time clock chip driver (for the ST M41T82) to use with hardware on my
custom board.  This is for 11.0.1.

The I2C driver works fine, but I can't seem to get my RTC driver to
load.  The m41t82_probe() function is never even called.

Both are loaded with kldload at the moment.

I think the problem is something in DRIVER_MODULE macro that is
preventing the kernel from even trying to let it probe.  One clue is
that if I change "iicbus" to "simplebus" in the DRIVER_MODULE macro
of the RTC, it will then at least call m41t82_probe().

It's like the kernel thinks that I have no iicbus driver and thus
won't even try to load the RTC module.

I have turned on "device iic" and "device iicbus" in my kernel config
file.

No messages are given when I try to load the m41t82 module.  It just
silently loads and does nothing.

Here is a code snippet from my I2C driver:
------------------------------------------

static driver_t i2c_driver = {
  "i2c",
  i2c_methods,
  sizeof(struct i2c_softc),
};
static devclass_t  i2c_devclass;

DRIVER_MODULE(iicbus, i2c, iicbus_driver, iicbus_devclass, 0, 0);
DRIVER_MODULE(i2c, simplebus, i2c_driver, i2c_devclass, 0, 0);

And here is a code snippet from my RTC driver:
----------------------------------------------

static device_method_t m41t82_methods[] = {
  DEVMETHOD(device_probe,         m41t82_probe),
  DEVMETHOD(device_attach,        m41t82_attach),
  DEVMETHOD(device_detach,        m41t82_detach),

  DEVMETHOD(clock_gettime,        m41t82_gettime),
  DEVMETHOD(clock_settime,        m41t82_settime),

  DEVMETHOD_END
};

static driver_t m41t82_driver = {
  "m41t82",
  m41t82_methods,
  sizeof(struct m41t82_softc),
};

static devclass_t m41t82_devclass;

DRIVER_MODULE(m41t82, iicbus, m41t82_driver, m41t82_devclass, NULL, NULL);
MODULE_VERSION(m41t82, 1);
MODULE_DEPEND(m41t82, iicbus, 1, 1, 1);

This is the relevant portion of my DTS file:
--------------------------------------------

  ps7io at e0000000 {
    device_type = "soc";
    compatible = "simple-bus";
    #address-cells = <0x1>;
    #size-cells = <0x1>;
    ranges = <0x0 0xe0000000 0x300000>;

    ... Other hardware ...

    i2c at 4000 {
      compatible = "xlnx,zy7_i2c";
      status = "okay";
      reg = <0x4000 0x1000>;
      #address-cells = <0x1>;
      #size-cells = <0x0>;

      rtc at d0 {
        status = "okay";
        compatible = "st,m41t82";
        reg = <0xd0>;
      };

    };
 };

Any clues about how to go about debugging this problem would be very
helpful.

Thanks,

Lee