On Mon, 7 Mar 2011, Sarah Sharp wrote: > The hcd->flags are in a sorry state. Some of them are clearly specific to > the particular roothub (HCD_POLL_RH, HCD_POLL_PENDING, and > HCD_WAKEUP_PENDING), but some flags are related to PCI device state > (HCD_HW_ACCESSIBLE and HCD_SAW_IRQ). This is an issue when one PCI device > can have two roothubs that share the same IRQ line and hardware. Okay, this patch is going to need a major overhaul in light of the changes to hcd->state. One simplification can be made easily enough. We should guarantee that usb_hc_died() always affects both hcds when called for a shared hcd. > Make sure to set HCD_FLAG_SAW_IRQ for both roothubs when an interrupt is > serviced, or an URB is unlinked without an interrupt. (We can't tell if > the host actually serviced an interrupt for a particular bus, but we can > tell it serviced some interrupt.) The SAW_IRQ stuff can all be removed later. > HCD_HW_ACCESSIBLE is set once by usb_add_hcd(), which is set for both > roothubs as they are added, so it doesn't need to be modified. > HCD_POLL_RH and HCD_POLL_PENDING are only checked by the USB core, and > they are never set by the xHCI driver, since the roothub never needs to be > polled. > > The usb_hcd's state field is a similar mess. Sometimes the state applies > to the underlying hardware: HC_STATE_HALT, HC_STATE_RUNNING, and > HC_STATE_QUIESCING. But sometimes the state refers to the roothub state: > HC_STATE_RESUMING and HC_STATE_SUSPENDED. > > This poses an issue with the xHCI split roothub, where two buses are > registered for one PCI device. Each bus in the xHCI split roothub can be > suspended separately, but both buses must be suspended before the PCI > device can be suspended. Therefore, make sure that the USB core checks > hcd->state equals HC_STATE_SUSPENDED for both roothubs before suspending > the PCI host. > > Make sure to kill off the shared roothub when the PCI resume fails. > > The xHCI driver will need to ensure that HC_STATE_HALT, HC_STATE_RUNNING, > and HC_STATE_QUIESCING will be set for both the roothubs. Fortunately this is no longer necessary, unless xhci-hcd uses hcd->state internally. > I'm not quite sure if the code in hcd_pci_suspend_noirq() is correct, > please check. If one roothub is halted, then both roothubs should be > halted (since they share the same hardware). But I suppose there could be > a race condition where one usb_hcd->state is set to HC_STATE_HALT, but the > other isn't yet? No, there's no race condition because by the time hcd_pci_suspend_noirq() is called, everything is quiescent. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
