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Re: kern/37279: usb and cdrom don't work after resume on PM branch

Some more information on the USB issue.

It appears that the Thinkpad's \_WAK method is responsible for powering off the external ports. I haven't had success powering them back on, as the ICH8 spec claims its EHCI doesn't support per-port power controls.

Here are a few theories of what we can try:

  1. Before we call AcpiLeaveSleepState on resume (which is responsible
     for invoking \_WAK), look for all EHCI devices and if the legacy
     capability is present, acquire the semaphore (see
     ehci_pci.c:ehci_get_ownership). With any luck, this will prevent
     SMI from turning the ports off on us.

  2. Failing #1, we need to decypher what method call in \_WAK is
     triggering the ports to power off and see if there is an AML method
     we can invoke to reverse the effect.


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