This is a note to let you know that I've just added the patch titled
xhci: Fix a race in usb2 LPM resume, blocking U3 for usb2 devices
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 dad67d5f3d0efe01d38c6cebcb6698280e51927b Mon Sep 17 00:00:00 2001
From: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
Date: Wed, 18 Nov 2015 10:48:22 +0200
Subject: xhci: Fix a race in usb2 LPM resume, blocking U3 for usb2 devices
Clear device initiated resume variables once device is fully up and running
in U0 state.
Resume needs to be signaled for 20ms for usb2 devices before they can be
moved to U0 state.
An interrupt is triggered if a device initiates resume. As we handle the
event in interrupt context we can not sleep for 20ms, so we instead set
a resume flag, a timestamp, and start the roothub polling.
The roothub code will later move the port to U0 when it finds a port in
resume state with the resume flag set, and timestamp passed by 20ms.
A host initiated resume is however not done in interrupt context, and
host initiated resume code will directly signal resume, wait 20ms and then
move the port to U0.
These two codepaths can race, if we are in the middle of a host initated
resume, while sleeping for 20ms, we may handle a port event and find the
port in resume state. The port event handling code will assume the resume
was device initiated and set the resume flag and timestamp.
Root hub code will however not catch the port in resume state again as the
host initated resume code has already moved the port to U0.
The resume flag and timestamp will remain set for this port preventing port
from suspending again (LPM setting port to U3)
Fix this for now by always clearing the device initated resume parameters
once port is in U0
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/host/xhci-hub.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
index 5d2d7e954bd4..0230965fb78c 100644
--- a/drivers/usb/host/xhci-hub.c
+++ b/drivers/usb/host/xhci-hub.c
@@ -782,12 +782,15 @@ static u32 xhci_get_port_status(struct usb_hcd *hcd,
status |= USB_PORT_STAT_SUSPEND;
}
}
- if ((raw_port_status & PORT_PLS_MASK) == XDEV_U0
- && (raw_port_status & PORT_POWER)
- && (bus_state->suspended_ports & (1 << wIndex))) {
- bus_state->suspended_ports &= ~(1 << wIndex);
- if (hcd->speed < HCD_USB3)
- bus_state->port_c_suspend |= 1 << wIndex;
+ if ((raw_port_status & PORT_PLS_MASK) == XDEV_U0 &&
+ (raw_port_status & PORT_POWER)) {
+ if (bus_state->suspended_ports & (1 << wIndex)) {
+ bus_state->suspended_ports &= ~(1 << wIndex);
+ if (hcd->speed < HCD_USB3)
+ bus_state->port_c_suspend |= 1 << wIndex;
+ }
+ bus_state->resume_done[wIndex] = 0;
+ clear_bit(wIndex, &bus_state->resuming_ports);
}
if (raw_port_status & PORT_CONNECT) {
status |= USB_PORT_STAT_CONNECTION;
--
2.6.2
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