linux-kernel - [PATCH 3.2 126/200] USB: EHCI: add delay during suspend to prevent erroneous wakeups

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <lsq.1396221815.380407735@decadent.org.uk>
Date:	Mon, 31 Mar 2014 00:23:35 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Alan Stern" <stern@...land.harvard.edu>,
	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
	"Peter Chen" <Peter.Chen@...escale.com>
Subject: [PATCH 3.2 126/200] USB: EHCI: add delay during suspend to
 prevent erroneous wakeups

3.2.56-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Alan Stern <stern@...land.harvard.edu>

commit 3e8d6d85adedc59115a564c0a54b36e42087c4d9 upstream.

High-speed USB connections revert back to full-speed signalling when
the device goes into suspend.  This takes several milliseconds, and
during that time it's not possible to tell reliably whether the device
has been disconnected.

On some platforms, the Wake-On-Disconnect circuitry gets confused
during this intermediate state.  It generates a false wakeup signal,
which can prevent the controller from going to sleep.

To avoid this problem, this patch adds a 5-ms delay to the
ehci_bus_suspend() routine if any ports have to switch over to
full-speed signalling.  (Actually, the delay was already present for
devices using a particular kind of PHY power management; the patch
merely causes the delay to be used more widely.)

Signed-off-by: Alan Stern <stern@...land.harvard.edu>
Reviewed-by: Peter Chen <Peter.Chen@...escale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
[bwh: Backported to 3.2:
 - Adjust context
 - s/has_tdi_phy_lpm/has_hostpc/
 - Always re-lock ehci->lock after the sleep]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/drivers/usb/host/ehci-hub.c
+++ b/drivers/usb/host/ehci-hub.c
@@ -207,6 +207,7 @@ static int ehci_bus_suspend (struct usb_
 	int			port;
 	int			mask;
 	int			changed;
+	bool			fs_idle_delay;
 
 	ehci_dbg(ehci, "suspend root hub\n");
 
@@ -249,6 +250,7 @@ static int ehci_bus_suspend (struct usb_
 	ehci->bus_suspended = 0;
 	ehci->owned_ports = 0;
 	changed = 0;
+	fs_idle_delay = false;
 	port = HCS_N_PORTS(ehci->hcs_params);
 	while (port--) {
 		u32 __iomem	*reg = &ehci->regs->port_status [port];
@@ -279,16 +281,34 @@ static int ehci_bus_suspend (struct usb_
 		if (t1 != t2) {
 			ehci_vdbg (ehci, "port %d, %08x -> %08x\n",
 				port + 1, t1, t2);
+			/*
+			 * On some controllers, Wake-On-Disconnect will
+			 * generate false wakeup signals until the bus
+			 * switches over to full-speed idle.  For their
+			 * sake, add a delay if we need one.
+			 */
+			if ((t2 & PORT_WKDISC_E) &&
+					ehci_port_speed(ehci, t2) ==
+						USB_PORT_STAT_HIGH_SPEED)
+				fs_idle_delay = true;
 			ehci_writel(ehci, t2, reg);
 			changed = 1;
 		}
 	}
+	spin_unlock_irq(&ehci->lock);
+
+	if ((changed && ehci->has_hostpc) || fs_idle_delay) {
+		/*
+		 * Wait for HCD to enter low-power mode or for the bus
+		 * to switch to full-speed idle.
+		 */
+		usleep_range(5000, 5500);
+	}
+
+	spin_lock_irq(&ehci->lock);
 
 	if (changed && ehci->has_hostpc) {
-		spin_unlock_irq(&ehci->lock);
-		msleep(5);	/* 5 ms for HCD to enter low-power mode */
 		spin_lock_irq(&ehci->lock);
-
 		port = HCS_N_PORTS(ehci->hcs_params);
 		while (port--) {
 			u32 __iomem	*hostpc_reg;

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/