Messages in this thread |  | | Subject | Re: [PATCH 2/3] xhci: Wait until link state trainsits to U0 after setting USB_SS_PORT_LS_U0 | From | Mathias Nyman <> | Date | Tue, 14 Jan 2020 16:48:40 +0200 |
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On 13.1.2020 11.18, Kai-Heng Feng wrote: > On Fri, Jan 10, 2020 at 11:27 PM Mathias Nyman > <mathias.nyman@linux.intel.com> wrote: >> >> On 3.1.2020 10.40, Kai-Heng Feng wrote: >>> Like U3 case, xHCI spec doesn't specify the upper bound of U0 transition >>> time. The 20ms is not enough for some devices. >>> >>> Intead of polling PLS or PLC, we can facilitate the port change event to >>> know that the link transits to U0 is completed. >>> >>> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com> >>> --- >>> drivers/usb/host/xhci-hub.c | 8 +++++++- >>> drivers/usb/host/xhci-mem.c | 1 + >>> drivers/usb/host/xhci-ring.c | 1 + >>> drivers/usb/host/xhci.h | 1 + >>> 4 files changed, 10 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c >>> index 2b2e9d004dbf..07886a1bce62 100644 >>> --- a/drivers/usb/host/xhci-hub.c >>> +++ b/drivers/usb/host/xhci-hub.c >>> @@ -1310,11 +1310,17 @@ int xhci_hub_control(struct usb_hcd *hcd, u16 typeReq, u16 wValue, >>> spin_lock_irqsave(&xhci->lock, flags); >>> } >>> } >>> + if (link_state == USB_SS_PORT_LS_U0) >>> + reinit_completion(&ports[wIndex]->link_state_changed); >> >> All the other suspend and resume related port flags/completions are >> in struct xhci_bus_state. See for example rexit_done[]. >> Not sure that is a better place but at least it would be consistent. >> >> Could actually make sense to move more of them to the xhci_port structure, >> but perhaps in some later suspend/resume rework patch. > > Ok. Should I keep this part of the patch as is? Or move it to > xhci_bus_state and probably move it back to xhci_port in later rework > patch?
Maybe move it to xhci_bus_state for now.
> >>> >>> xhci_set_link_state(xhci, ports[wIndex], link_state); >>> >>> spin_unlock_irqrestore(&xhci->lock, flags); >>> - msleep(20); /* wait device to enter */ >>> + if (link_state == USB_SS_PORT_LS_U0) { >>> + if (!wait_for_completion_timeout(&ports[wIndex]->link_state_changed, msecs_to_jiffies(100))) >>> + xhci_dbg(xhci, "missing U0 port change event for port %d-%d\n", hcd->self.busnum, wIndex + 1); >> >> We might be waiting for completion here in unnecessary. >> No completion is called if port is already in U0, either set by >> xhci_bus_resume(), or we race with a device initiated resume. > > Is there a way to know if device initiated resume is inplace?
Yes, before xhci interrupt handler handles the device initiated resume PLS is XDEV_RESUME and PLC is set.
After the interrupt handler PLS goes from XDEV_RESUME to XDEV_RECOVERY to XDEV_U0. A bit is set for bus_state->port_remote_wakeup, and on usb core side also bus->resuming_ports |= bit is set, (having both may be a bit redundant, we might be able to get rid of bus_state->port_remote_wakeup, but not right now)
> >> >> Maybe read the current port link state first, and don't do anything if it's >> already in U0, or fail if it's in a state where we can't resume to U0. > > What happens if device initiated resume happens right after we query the PLS?
Not sure, fortunately the drivers task is to write XDEV_U0 to PLS both when we want a host initiated resume, or when we want to react on a device initiated resume. So hopefully that's ok, but this race exists.
Better keep calling completion for both host and device initiated resume cases when port reaches U0/U1/U2 to avoid waiting for the completion unnecessary, like you current patch does. -Mathias
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