patch "xhci: fix oops when xhci resumes from hibernate with hw lpm capable" added to usb tree

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This is a note to let you know that I've just added the patch titled

    xhci: fix oops when xhci resumes from hibernate with hw lpm capable

to my usb git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.

If you have any questions about this process, please let me know.


>From 96044694b8511bc2b04df0776b4ba295cfe005c0 Mon Sep 17 00:00:00 2001
From: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
Date: Thu, 11 Sep 2014 13:55:50 +0300
Subject: xhci: fix oops when xhci resumes from hibernate with hw lpm capable
 devices

Resuming from hibernate (S4) will restart and re-initialize xHC.
The device contexts are freed and will be re-allocated later during device reset.

Usb core will disable link pm in device resume before device reset, which will
try to change the max exit latency, accessing the device contexts before they are re-allocated.

There is no need to zero (disable) the max exit latency when disabling hw lpm
for a freshly re-initialized xHC. So check that device context exists before
doing anything. The max exit latency will be set again after device reset when usb core
enables the link pm.

Reported-by: Imre Deak <imre.deak@xxxxxxxxx>
Tested-by: Imre Deak <imre.deak@xxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/usb/host/xhci.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index c020b094fe7d..c4a8fca8ae93 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -3971,13 +3971,21 @@ static int __maybe_unused xhci_change_max_exit_latency(struct xhci_hcd *xhci,
 	int ret;
 
 	spin_lock_irqsave(&xhci->lock, flags);
-	if (max_exit_latency == xhci->devs[udev->slot_id]->current_mel) {
+
+	virt_dev = xhci->devs[udev->slot_id];
+
+	/*
+	 * virt_dev might not exists yet if xHC resumed from hibernate (S4) and
+	 * xHC was re-initialized. Exit latency will be set later after
+	 * hub_port_finish_reset() is done and xhci->devs[] are re-allocated
+	 */
+
+	if (!virt_dev || max_exit_latency == virt_dev->current_mel) {
 		spin_unlock_irqrestore(&xhci->lock, flags);
 		return 0;
 	}
 
 	/* Attempt to issue an Evaluate Context command to change the MEL. */
-	virt_dev = xhci->devs[udev->slot_id];
 	command = xhci->lpm_command;
 	ctrl_ctx = xhci_get_input_control_ctx(xhci, command->in_ctx);
 	if (!ctrl_ctx) {
-- 
2.1.0


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