Commit eb002726 authored Mar 12, 2020 by Kai-Heng Feng Committed by Greg Kroah-Hartman Mar 12, 2020

xhci: Ensure link state is U3 after setting USB_SS_PORT_LS_U3



The xHCI spec doesn't specify the upper bound of U3 transition time. For
some devices 20ms is not enough, so we need to make sure the link state
is in U3 before further actions.

I've tried to use U3 Entry Capability by setting U3 Entry Enable in
config register, however the port change event for U3 transition
interrupts the system suspend process.

For now let's use the less ideal method by polling PLS.

[use usleep_range(), and shorten the delay time while polling -Mathias]
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20200312144517.1593-7-mathias.nyman@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent cbb23d55

drivers/usb/host/xhci-hub.c

+10 −1

Original line number	Diff line number	Diff line
		@@ -1324,7 +1324,16 @@ int xhci_hub_control(struct usb_hcd *hcd, u16 typeReq, u16 wValue,
		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_U3) {
		int retries = 16;

		while (retries--) {
		usleep_range(4000, 8000);
		temp = readl(ports[wIndex]->addr);
		if ((temp & PORT_PLS_MASK) == XDEV_U3)
		break;
		}
		}
		spin_lock_irqsave(&xhci->lock, flags);

		temp = readl(ports[wIndex]->addr);

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