Have you checked if the 82576LM PHY is powered and alive? I.e. does the PHY link after power-up? Do LEDs turn on? I"m asking in order to rule out any hardware issue with the PHY that might prevent it from responding to your code in your test.
Have you checked your code against our e1000e open source driver? Specifically comparing the PHY and semaphore usage when accessing MDIC register against our code. This needs to be followed exactly as the Intel driver.
You can get a copy of e1000e driver here:
Hope this is helpful. Let us know if there further questions.