usb: Don't enable USB 2.0 Link PM by default.

How it's supposed to work:
--------------------------

USB 2.0 Link PM is a lower power state that some newer USB 2.0 devices
support.  USB 3.0 devices certified by the USB-IF are required to
support it if they are plugged into a USB 2.0 only port, or a USB 2.0
cable is used.  USB 2.0 Link PM requires both a USB device and a host
controller that supports USB 2.0 hardware-enabled LPM.

USB 2.0 Link PM is designed to be enabled once by software, and the host
hardware handles transitions to the L1 state automatically.  The premise
of USB 2.0 Link PM is to be able to put the device into a lower power
link state when the bus is idle or the device NAKs USB IN transfers for
a specified amount of time.

...but hardware is broken:
--------------------------

It turns out many USB 3.0 devices claim to support USB 2.0 Link PM (by
setting the LPM bit in their USB 2.0 BOS descriptor), but they don't
actually implement it correctly.  This manifests as the USB device
refusing to respond to transfers when it is plugged into a USB 2.0 only
port under the Haswell-ULT/Lynx Point LP xHCI host.

These devices pass the xHCI driver's simple test to enable USB 2.0 Link
PM, wait for the port to enter L1, and then bring it back into L0.  They
only start to break when L1 entry is interleaved with transfers.

Some devices then fail to respond to the next control transfer (usually
a Set Configuration).  This results in devices never enumerating.

Other mass storage devices (such as a later model Western Digital My
Passport USB 3.0 hard drive) respond fine to going into L1 between
control transfers.  They ACK the entry, come out of L1 when the host
needs to send a control transfer, and respond properly to those control
transfers.  However, when the first READ10 SCSI command is sent, the
device NAKs the data phase while it's reading from the spinning disk.
Eventually, the host requests to put the link into L1, and the device
ACKs that request.  Then it never responds to the data phase of the
READ10 command.  This results in not being able to read from the drive.

Some mass storage devices (like the Corsair Survivor USB 3.0 flash
drive) are well behaved.  They ACK the entry into L1 during control
transfers, and when SCSI commands start coming in, they NAK the requests
to go into L1, because they need to be at full power.

Not all USB 3.0 devices advertise USB 2.0 link PM support.  My Point
Grey USB 3.0 webcam advertises itself as a USB 2.1 device, but doesn't
have a USB 2.0 BOS descriptor, so we don't enable USB 2.0 Link PM.  I
suspect that means the device isn't certified.

What do we do about it?
-----------------------

There's really no good way for the kernel to test these devices.
Therefore, the kernel needs to disable USB 2.0 Link PM by default, and
distros will have to enable it by writing 1 to the sysfs file
/sys/bus/usb/devices/../power/usb2_hardware_lpm.  Rip out the xHCI Link
PM test, since it's not sufficient to detect these buggy devices, and
don't automatically enable LPM after the device is addressed.

This patch should be backported to kernels as old as 3.11, that
contain the commit a558ccd "usb: xhci:
add USB2 Link power management BESL support".  Without this fix, some
USB 3.0 devices will not enumerate or work properly under USB 2.0 ports
on Haswell-ULT systems.

Signed-off-by: Sarah Sharp <[email protected]>
Cc: [email protected]

Author: Sarah Sharp

drivers/usb/core/driver.c

@@ -1790,6 +1790,9 @@ int usb_set_usb2_hardware_lpm(struct usb_device *udev, int enable)
 	struct usb_hcd *hcd = bus_to_hcd(udev->bus);
 	int ret = -EPERM;
 
+	if (enable && !udev->usb2_hw_lpm_allowed)
+		return 0;
+
 	if (hcd->driver->set_usb2_hw_lpm) {
 		ret = hcd->driver->set_usb2_hw_lpm(hcd, udev, enable);
 		if (!ret)

drivers/usb/core/hub.c

@@ -5203,6 +5203,7 @@ static int usb_reset_and_verify_device(struct usb_device *udev)
 
 done:
 	/* Now that the alt settings are re-installed, enable LTM and LPM. */
+	usb_set_usb2_hardware_lpm(udev, 1);
 	usb_unlocked_enable_lpm(udev);
 	usb_enable_ltm(udev);
 	usb_release_bos_descriptor(udev);

drivers/usb/core/sysfs.c

@@ -458,7 +458,7 @@ static ssize_t usb2_hardware_lpm_show(struct device *dev,
 	struct usb_device *udev = to_usb_device(dev);
 	const char *p;
 
-	if (udev->usb2_hw_lpm_enabled == 1)
+	if (udev->usb2_hw_lpm_allowed == 1)
 		p = "enabled";
 	else
 		p = "disabled";
@@ -478,8 +478,10 @@ static ssize_t usb2_hardware_lpm_store(struct device *dev,
 
 	ret = strtobool(buf, &value);
 
-	if (!ret)
+	if (!ret) {
+		udev->usb2_hw_lpm_allowed = value;
 		ret = usb_set_usb2_hardware_lpm(udev, value);
+	}
 
 	usb_unlock_device(udev);
 

drivers/usb/host/xhci-mem.c

@@ -1693,9 +1693,7 @@ void xhci_free_command(struct xhci_hcd *xhci,
 void xhci_mem_cleanup(struct xhci_hcd *xhci)
 {
 	struct pci_dev	*pdev = to_pci_dev(xhci_to_hcd(xhci)->self.controller);
-	struct dev_info	*dev_info, *next;
 	struct xhci_cd  *cur_cd, *next_cd;
-	unsigned long	flags;
 	int size;
 	int i, j, num_ports;
 
@@ -1756,13 +1754,6 @@ void xhci_mem_cleanup(struct xhci_hcd *xhci)
 
 	scratchpad_free(xhci);
 
-	spin_lock_irqsave(&xhci->lock, flags);
-	list_for_each_entry_safe(dev_info, next, &xhci->lpm_failed_devs, list) {
-		list_del(&dev_info->list);
-		kfree(dev_info);
-	}
-	spin_unlock_irqrestore(&xhci->lock, flags);
-
 	if (!xhci->rh_bw)
 		goto no_bw;
 
@@ -2231,7 +2222,6 @@ int xhci_mem_init(struct xhci_hcd *xhci, gfp_t flags)
 	u32 page_size, temp;
 	int i;
 
-	INIT_LIST_HEAD(&xhci->lpm_failed_devs);
 	INIT_LIST_HEAD(&xhci->cancel_cmd_list);
 
 	page_size = xhci_readl(xhci, &xhci->op_regs->page_size);

drivers/usb/host/xhci.c

@@ -4013,133 +4013,6 @@ static int xhci_calculate_usb2_hw_lpm_params(struct usb_device *udev)
 	return PORT_BESLD(besld) | PORT_L1_TIMEOUT(l1) | PORT_HIRDM(hirdm);
 }
 
-static int xhci_usb2_software_lpm_test(struct usb_hcd *hcd,
-					struct usb_device *udev)
-{
-	struct xhci_hcd	*xhci = hcd_to_xhci(hcd);
-	struct dev_info	*dev_info;
-	__le32 __iomem	**port_array;
-	__le32 __iomem	*addr, *pm_addr;
-	u32		temp, dev_id;
-	unsigned int	port_num;
-	unsigned long	flags;
-	int		hird;
-	int		ret;
-
-	if (hcd->speed == HCD_USB3 || !xhci->sw_lpm_support ||
-			!udev->lpm_capable)
-		return -EINVAL;
-
-	/* we only support lpm for non-hub device connected to root hub yet */
-	if (!udev->parent || udev->parent->parent ||
-			udev->descriptor.bDeviceClass == USB_CLASS_HUB)
-		return -EINVAL;
-
-	spin_lock_irqsave(&xhci->lock, flags);
-
-	/* Look for devices in lpm_failed_devs list */
-	dev_id = le16_to_cpu(udev->descriptor.idVendor) << 16 |
-			le16_to_cpu(udev->descriptor.idProduct);
-	list_for_each_entry(dev_info, &xhci->lpm_failed_devs, list) {
-		if (dev_info->dev_id == dev_id) {
-			ret = -EINVAL;
-			goto finish;
-		}
-	}
-
-	port_array = xhci->usb2_ports;
-	port_num = udev->portnum - 1;
-
-	if (port_num > HCS_MAX_PORTS(xhci->hcs_params1)) {
-		xhci_dbg(xhci, "invalid port number %d\n", udev->portnum);
-		ret = -EINVAL;
-		goto finish;
-	}
-
-	/*
-	 * Test USB 2.0 software LPM.
-	 * FIXME: some xHCI 1.0 hosts may implement a new register to set up
-	 * hardware-controlled USB 2.0 LPM. See section 5.4.11 and 4.23.5.1.1.1
-	 * in the June 2011 errata release.
-	 */
-	xhci_dbg(xhci, "test port %d software LPM\n", port_num);
-	/*
-	 * Set L1 Device Slot and HIRD/BESL.
-	 * Check device's USB 2.0 extension descriptor to determine whether
-	 * HIRD or BESL shoule be used. See USB2.0 LPM errata.
-	 */
-	pm_addr = port_array[port_num] + PORTPMSC;
-	hird = xhci_calculate_hird_besl(xhci, udev);
-	temp = PORT_L1DS(udev->slot_id) | PORT_HIRD(hird);
-	xhci_writel(xhci, temp, pm_addr);
-
-	/* Set port link state to U2(L1) */
-	addr = port_array[port_num];
-	xhci_set_link_state(xhci, port_array, port_num, XDEV_U2);
-
-	/* wait for ACK */
-	spin_unlock_irqrestore(&xhci->lock, flags);
-	msleep(10);
-	spin_lock_irqsave(&xhci->lock, flags);
-
-	/* Check L1 Status */
-	ret = xhci_handshake(xhci, pm_addr,
-			PORT_L1S_MASK, PORT_L1S_SUCCESS, 125);
-	if (ret != -ETIMEDOUT) {
-		/* enter L1 successfully */
-		temp = xhci_readl(xhci, addr);
-		xhci_dbg(xhci, "port %d entered L1 state, port status 0x%x\n",
-				port_num, temp);
-		ret = 0;
-	} else {
-		temp = xhci_readl(xhci, pm_addr);
-		xhci_dbg(xhci, "port %d software lpm failed, L1 status %d\n",
-				port_num, temp & PORT_L1S_MASK);
-		ret = -EINVAL;
-	}
-
-	/* Resume the port */
-	xhci_set_link_state(xhci, port_array, port_num, XDEV_U0);
-
-	spin_unlock_irqrestore(&xhci->lock, flags);
-	msleep(10);
-	spin_lock_irqsave(&xhci->lock, flags);
-
-	/* Clear PLC */
-	xhci_test_and_clear_bit(xhci, port_array, port_num, PORT_PLC);
-
-	/* Check PORTSC to make sure the device is in the right state */
-	if (!ret) {
-		temp = xhci_readl(xhci, addr);
-		xhci_dbg(xhci, "resumed port %d status 0x%x\n",	port_num, temp);
-		if (!(temp & PORT_CONNECT) || !(temp & PORT_PE) ||
-				(temp & PORT_PLS_MASK) != XDEV_U0) {
-			xhci_dbg(xhci, "port L1 resume fail\n");
-			ret = -EINVAL;
-		}
-	}
-
-	if (ret) {
-		/* Insert dev to lpm_failed_devs list */
-		xhci_warn(xhci, "device LPM test failed, may disconnect and "
-				"re-enumerate\n");
-		dev_info = kzalloc(sizeof(struct dev_info), GFP_ATOMIC);
-		if (!dev_info) {
-			ret = -ENOMEM;
-			goto finish;
-		}
-		dev_info->dev_id = dev_id;
-		INIT_LIST_HEAD(&dev_info->list);
-		list_add(&dev_info->list, &xhci->lpm_failed_devs);
-	} else {
-		xhci_ring_device(xhci, udev->slot_id);
-	}
-
-finish:
-	spin_unlock_irqrestore(&xhci->lock, flags);
-	return ret;
-}
-
 int xhci_set_usb2_hardware_lpm(struct usb_hcd *hcd,
 			struct usb_device *udev, int enable)
 {
@@ -4267,24 +4140,26 @@ static int xhci_check_usb2_port_capability(struct xhci_hcd *xhci, int port,
 int xhci_update_device(struct usb_hcd *hcd, struct usb_device *udev)
 {
 	struct xhci_hcd	*xhci = hcd_to_xhci(hcd);
-	int		ret;
 	int		portnum = udev->portnum - 1;
 
-	ret = xhci_usb2_software_lpm_test(hcd, udev);
-	if (!ret) {
-		xhci_dbg(xhci, "software LPM test succeed\n");
-		if (xhci->hw_lpm_support == 1 &&
-		    xhci_check_usb2_port_capability(xhci, portnum, XHCI_HLC)) {
-			udev->usb2_hw_lpm_capable = 1;
-			udev->l1_params.timeout = XHCI_L1_TIMEOUT;
-			udev->l1_params.besl = XHCI_DEFAULT_BESL;
-			if (xhci_check_usb2_port_capability(xhci, portnum,
-							    XHCI_BLC))
-				udev->usb2_hw_lpm_besl_capable = 1;
-			ret = xhci_set_usb2_hardware_lpm(hcd, udev, 1);
-			if (!ret)
-				udev->usb2_hw_lpm_enabled = 1;
-		}
+	if (hcd->speed == HCD_USB3 || !xhci->sw_lpm_support ||
+			!udev->lpm_capable)
+		return 0;
+
+	/* we only support lpm for non-hub device connected to root hub yet */
+	if (!udev->parent || udev->parent->parent ||
+			udev->descriptor.bDeviceClass == USB_CLASS_HUB)
+		return 0;
+
+	if (xhci->hw_lpm_support == 1 &&
+			xhci_check_usb2_port_capability(
+				xhci, portnum, XHCI_HLC)) {
+		udev->usb2_hw_lpm_capable = 1;
+		udev->l1_params.timeout = XHCI_L1_TIMEOUT;
+		udev->l1_params.besl = XHCI_DEFAULT_BESL;
+		if (xhci_check_usb2_port_capability(xhci, portnum,
+					XHCI_BLC))
+			udev->usb2_hw_lpm_besl_capable = 1;
 	}
 
 	return 0;

include/linux/usb.h

@@ -475,7 +475,8 @@ struct usb3_lpm_parameters {
  * @lpm_capable: device supports LPM
  * @usb2_hw_lpm_capable: device can perform USB2 hardware LPM
  * @usb2_hw_lpm_besl_capable: device can perform USB2 hardware BESL LPM
- * @usb2_hw_lpm_enabled: USB2 hardware LPM enabled
+ * @usb2_hw_lpm_enabled: USB2 hardware LPM is enabled
+ * @usb2_hw_lpm_allowed: Userspace allows USB 2.0 LPM to be enabled
  * @usb3_lpm_enabled: USB3 hardware LPM enabled
  * @string_langid: language ID for strings
  * @product: iProduct string, if present (static)
@@ -548,6 +549,7 @@ struct usb_device {
 	unsigned usb2_hw_lpm_capable:1;
 	unsigned usb2_hw_lpm_besl_capable:1;
 	unsigned usb2_hw_lpm_enabled:1;
+	unsigned usb2_hw_lpm_allowed:1;
 	unsigned usb3_lpm_enabled:1;
 	int string_langid;