[coreboot] USB EHCI power management

[Аладышев Константин]

I have a problem with USB EHCI on board with Lynxpoint-LP southbridge.

First of all system doesn't wakeup from USB devices from S3. EHCI controller
is listed in "/proc/acpi/wakeup" as "enabled" and GPE number is seemed to be
configured correctly to PME_B0, but it doesn't work.

More troubling issue that USB stops working after wakeup (for example from
power button).

In attempt to solve this issue I started to  investigate how exactly EHCI
works in S3 suspend/resume sequence.

And I have some questions:

1) PCI_config: PWR_CNTL_STS register (54-55h)

What power state should enter EHCI controller when system enters S3?   D0
state or D3hot ?

2) MEM_BASE: USB2.0_CMD (20-23h)

Is it correct, that system disables "Run/Stop (RS)" bit when system enters
S3?  

3) MEM_BASE: RMHPORTSTSN (F0h)

Is it correct, that all ports became suspended when system enters S3?

4) Who is responsible to set "Run/Stop (RS)" and bring USB ports from
suspended state? BIOS or OS?

5) Is there any board in coreboot that has USB EHCI working correctly with
S3 suspend/resume?