Hi Mario & Mathias,
According to xHCI spec v1.2: A.1.2 Power State Definitions:
Software shall place each downstream USB port with power
enabled into the Suspend or Disabled state before it
attempts to move the xHC out of the D0 power state.
But I have not found any USB core code does it, do you have any ideas
about it?
We have added the similar codes at non-PCI USB platform, but met above
concerns. In fact, we met kernel dump that the thread usb-storage try
to access the port status when the platform xHCI code has already put
the controller to D3.
Best regards,
Peter
This is pretty tangential to my patch. But FWIW in case you missed we're
going to discard this patch in favor of another approach in PCI core.
Regarding your point though If I'm not mistaken this should be handled by
the Linux parent/child device model. Each of the ports should be children
of the hub they're connected to and the hub a child of the controller. So
when doing any actions that start runtime PM on the host controller the
children need to first be in runtime PM.
It seems there is no runtime PM suspend for xhci and USB core at
.shutdown currently. Alan & Mathias, please correct me if I was wrong.
I think you are right. At shutdown we only halt the xHC.
We don't force ports to suspend or disable state.
We only put some selected xHC to D3
USB 2 ports might suspend themselves if there is no activity.
Doesn't seem like usb core hcd code, or hub driver does anything either.
Thanks
Mathias
