USB: Link PM fixes and Latency Tolerance Messaging

Hi Greg,
 
 Here's four bug fix patches for Link PM (LPM), which are marked for
 3.5-stable.  There's also three patches that turn on Latency Tolerance
 Messaging (LTM) for xHCI host controllers and USB 3.0 devices that support
 this low power feature.
 
 Please queue for 3.6.
 
 Sarah Sharp
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Merge tag 'for-usb-next-2012-07-11' of git://git.kernel.org/pub/scm/linux/kernel/git/sarah/xhci into usb-next

USB: Link PM fixes and Latency Tolerance Messaging

Hi Greg,

Here's four bug fix patches for Link PM (LPM), which are marked for
3.5-stable.  There's also three patches that turn on Latency Tolerance
Messaging (LTM) for xHCI host controllers and USB 3.0 devices that support
this low power feature.

Please queue for 3.6.

Sarah Sharp

Documentation/ABI/testing/sysfs-bus-usb

@@ -208,3 +208,15 @@ Description:
 		such as ACPI. This file will read either "removable" or
 		"fixed" if the information is available, and "unknown"
 		otherwise.
+
+What:		/sys/bus/usb/devices/.../ltm_capable
+Date:		July 2012
+Contact:	Sarah Sharp <sarah.a.sharp@linux.intel.com>
+Description:
+		USB 3.0 devices may optionally support Latency Tolerance
+		Messaging (LTM).  They indicate their support by setting a bit
+		in the bmAttributes field of their SuperSpeed BOS descriptors.
+		If that bit is set for the device, ltm_capable will read "yes".
+		If the device doesn't support LTM, the file will read "no".
+		The file will be present for all speeds of USB devices, and will
+		always read "no" for USB 1.1 and USB 2.0 devices.

drivers/usb/core/hub.c

@@ -2614,6 +2614,50 @@ static int check_port_resume_type(struct usb_device *udev,
 	return status;
 }
 
+int usb_disable_ltm(struct usb_device *udev)
+{
+	struct usb_hcd *hcd = bus_to_hcd(udev->bus);
+
+	/* Check if the roothub and device supports LTM. */
+	if (!usb_device_supports_ltm(hcd->self.root_hub) ||
+			!usb_device_supports_ltm(udev))
+		return 0;
+
+	/* Clear Feature LTM Enable can only be sent if the device is
+	 * configured.
+	 */
+	if (!udev->actconfig)
+		return 0;
+
+	return usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
+			USB_REQ_CLEAR_FEATURE, USB_RECIP_DEVICE,
+			USB_DEVICE_LTM_ENABLE, 0, NULL, 0,
+			USB_CTRL_SET_TIMEOUT);
+}
+EXPORT_SYMBOL_GPL(usb_disable_ltm);
+
+void usb_enable_ltm(struct usb_device *udev)
+{
+	struct usb_hcd *hcd = bus_to_hcd(udev->bus);
+
+	/* Check if the roothub and device supports LTM. */
+	if (!usb_device_supports_ltm(hcd->self.root_hub) ||
+			!usb_device_supports_ltm(udev))
+		return;
+
+	/* Set Feature LTM Enable can only be sent if the device is
+	 * configured.
+	 */
+	if (!udev->actconfig)
+		return;
+
+	usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
+			USB_REQ_SET_FEATURE, USB_RECIP_DEVICE,
+			USB_DEVICE_LTM_ENABLE, 0, NULL, 0,
+			USB_CTRL_SET_TIMEOUT);
+}
+EXPORT_SYMBOL_GPL(usb_enable_ltm);
+
 #ifdef	CONFIG_USB_SUSPEND
 
 /*
@@ -2709,6 +2753,11 @@ int usb_port_suspend(struct usb_device *udev, pm_message_t msg)
 	if (udev->usb2_hw_lpm_enabled == 1)
 		usb_set_usb2_hardware_lpm(udev, 0);
 
+	if (usb_disable_ltm(udev)) {
+		dev_err(&udev->dev, "%s Failed to disable LTM before suspend\n.",
+				__func__);
+		return -ENOMEM;
+	}
 	if (usb_unlocked_disable_lpm(udev)) {
 		dev_err(&udev->dev, "%s Failed to disable LPM before suspend\n.",
 				__func__);
@@ -2738,7 +2787,8 @@ int usb_port_suspend(struct usb_device *udev, pm_message_t msg)
 		if (udev->usb2_hw_lpm_capable == 1)
 			usb_set_usb2_hardware_lpm(udev, 1);
 
-		/* Try to enable USB3 LPM again */
+		/* Try to enable USB3 LTM and LPM again */
+		usb_enable_ltm(udev);
 		usb_unlocked_enable_lpm(udev);
 
 		/* System sleep transitions should never fail */
@@ -2939,7 +2989,8 @@ int usb_port_resume(struct usb_device *udev, pm_message_t msg)
 		if (udev->usb2_hw_lpm_capable == 1)
 			usb_set_usb2_hardware_lpm(udev, 1);
 
-		/* Try to enable USB3 LPM */
+		/* Try to enable USB3 LTM and LPM */
+		usb_enable_ltm(udev);
 		usb_unlocked_enable_lpm(udev);
 	}
 
@@ -3492,6 +3543,15 @@ EXPORT_SYMBOL_GPL(usb_unlocked_disable_lpm);
 
 void usb_unlocked_enable_lpm(struct usb_device *udev) { }
 EXPORT_SYMBOL_GPL(usb_unlocked_enable_lpm);
+
+int usb_disable_ltm(struct usb_device *udev)
+{
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_disable_ltm);
+
+void usb_enable_ltm(struct usb_device *udev) { }
+EXPORT_SYMBOL_GPL(usb_enable_ltm);
 #endif
 
 
@@ -4675,6 +4735,23 @@ static int usb_reset_and_verify_device(struct usb_device *udev)
 	}
 	parent_hub = hdev_to_hub(parent_hdev);
 
+	/* Disable LPM and LTM while we reset the device and reinstall the alt
+	 * settings.  Device-initiated LPM settings, and system exit latency
+	 * settings are cleared when the device is reset, so we have to set
+	 * them up again.
+	 */
+	ret = usb_unlocked_disable_lpm(udev);
+	if (ret) {
+		dev_err(&udev->dev, "%s Failed to disable LPM\n.", __func__);
+		goto re_enumerate;
+	}
+	ret = usb_disable_ltm(udev);
+	if (ret) {
+		dev_err(&udev->dev, "%s Failed to disable LTM\n.",
+				__func__);
+		goto re_enumerate;
+	}
+
 	set_bit(port1, parent_hub->busy_bits);
 	for (i = 0; i < SET_CONFIG_TRIES; ++i) {
 
@@ -4702,22 +4779,11 @@ static int usb_reset_and_verify_device(struct usb_device *udev)
 		goto done;
 
 	mutex_lock(hcd->bandwidth_mutex);
-	/* Disable LPM while we reset the device and reinstall the alt settings.
-	 * Device-initiated LPM settings, and system exit latency settings are
-	 * cleared when the device is reset, so we have to set them up again.
-	 */
-	ret = usb_disable_lpm(udev);
-	if (ret) {
-		dev_err(&udev->dev, "%s Failed to disable LPM\n.", __func__);
-		mutex_unlock(hcd->bandwidth_mutex);
-		goto done;
-	}
 	ret = usb_hcd_alloc_bandwidth(udev, udev->actconfig, NULL, NULL);
 	if (ret < 0) {
 		dev_warn(&udev->dev,
 				"Busted HC?  Not enough HCD resources for "
 				"old configuration.\n");
-		usb_enable_lpm(udev);
 		mutex_unlock(hcd->bandwidth_mutex);
 		goto re_enumerate;
 	}
@@ -4729,7 +4795,6 @@ static int usb_reset_and_verify_device(struct usb_device *udev)
 		dev_err(&udev->dev,
 			"can't restore configuration #%d (error=%d)\n",
 			udev->actconfig->desc.bConfigurationValue, ret);
-		usb_enable_lpm(udev);
 		mutex_unlock(hcd->bandwidth_mutex);
 		goto re_enumerate;
   	}
@@ -4768,17 +4833,18 @@ static int usb_reset_and_verify_device(struct usb_device *udev)
 				desc->bInterfaceNumber,
 				desc->bAlternateSetting,
 				ret);
-			usb_unlocked_enable_lpm(udev);
 			goto re_enumerate;
 		}
 	}
 
-	/* Now that the alt settings are re-installed, enable LPM. */
-	usb_unlocked_enable_lpm(udev);
 done:
+	/* Now that the alt settings are re-installed, enable LTM and LPM. */
+	usb_unlocked_enable_lpm(udev);
+	usb_enable_ltm(udev);
 	return 0;
  
 re_enumerate:
+	/* LPM state doesn't matter when we're about to destroy the device. */
 	hub_port_logical_disconnect(parent_hub, port1);
 	return -ENODEV;
 }

drivers/usb/core/message.c

@@ -1174,6 +1174,8 @@ void usb_disable_device(struct usb_device *dev, int skip_ep0)
 			put_device(&dev->actconfig->interface[i]->dev);
 			dev->actconfig->interface[i] = NULL;
 		}
+		usb_unlocked_disable_lpm(dev);
+		usb_disable_ltm(dev);
 		dev->actconfig = NULL;
 		if (dev->state == USB_STATE_CONFIGURED)
 			usb_set_device_state(dev, USB_STATE_ADDRESS);
@@ -1792,14 +1794,15 @@ free_interfaces:
 	 * installed, so that the xHCI driver can recalculate the U1/U2
 	 * timeouts.
 	 */
-	if (usb_disable_lpm(dev)) {
+	if (dev->actconfig && usb_disable_lpm(dev)) {
 		dev_err(&dev->dev, "%s Failed to disable LPM\n.", __func__);
 		mutex_unlock(hcd->bandwidth_mutex);
 		return -ENOMEM;
 	}
 	ret = usb_hcd_alloc_bandwidth(dev, cp, NULL, NULL);
 	if (ret < 0) {
-		usb_enable_lpm(dev);
+		if (dev->actconfig)
+			usb_enable_lpm(dev);
 		mutex_unlock(hcd->bandwidth_mutex);
 		usb_autosuspend_device(dev);
 		goto free_interfaces;
@@ -1819,7 +1822,7 @@ free_interfaces:
 	if (!cp) {
 		usb_set_device_state(dev, USB_STATE_ADDRESS);
 		usb_hcd_alloc_bandwidth(dev, NULL, NULL, NULL);
-		usb_enable_lpm(dev);
+		/* Leave LPM disabled while the device is unconfigured. */
 		mutex_unlock(hcd->bandwidth_mutex);
 		usb_autosuspend_device(dev);
 		goto free_interfaces;
@@ -1877,6 +1880,8 @@ free_interfaces:
 
 	/* Now that the interfaces are installed, re-enable LPM. */
 	usb_unlocked_enable_lpm(dev);
+	/* Enable LTM if it was turned off by usb_disable_device. */
+	usb_enable_ltm(dev);
 
 	/* Now that all the interfaces are set up, register them
 	 * to trigger binding of drivers to interfaces.  probe()

drivers/usb/core/sysfs.c

@@ -253,6 +253,15 @@ show_removable(struct device *dev, struct device_attribute *attr, char *buf)
 }
 static DEVICE_ATTR(removable, S_IRUGO, show_removable, NULL);
 
+static ssize_t
+show_ltm_capable(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	if (usb_device_supports_ltm(to_usb_device(dev)))
+		return sprintf(buf, "%s\n", "yes");
+	return sprintf(buf, "%s\n", "no");
+}
+static DEVICE_ATTR(ltm_capable, S_IRUGO, show_ltm_capable, NULL);
+
 #ifdef	CONFIG_PM
 
 static ssize_t
@@ -649,6 +658,7 @@ static struct attribute *dev_attrs[] = {
 	&dev_attr_authorized.attr,
 	&dev_attr_remove.attr,
 	&dev_attr_removable.attr,
+	&dev_attr_ltm_capable.attr,
 	NULL,
 };
 static struct attribute_group dev_attr_grp = {

drivers/usb/core/usb.c

@@ -396,6 +396,7 @@ struct usb_device *usb_alloc_dev(struct usb_device *parent,
 	dev->dev.dma_mask = bus->controller->dma_mask;
 	set_dev_node(&dev->dev, dev_to_node(bus->controller));
 	dev->state = USB_STATE_ATTACHED;
+	dev->lpm_disable_count = 1;
 	atomic_set(&dev->urbnum, 0);
 
 	INIT_LIST_HEAD(&dev->ep0.urb_list);

drivers/usb/host/xhci-hub.c

@@ -544,12 +544,18 @@ int xhci_hub_control(struct usb_hcd *hcd, u16 typeReq, u16 wValue,
 		if (hcd->speed != HCD_USB3)
 			goto error;
 
+		/* Set the U1 and U2 exit latencies. */
 		memcpy(buf, &usb_bos_descriptor,
 				USB_DT_BOS_SIZE + USB_DT_USB_SS_CAP_SIZE);
 		temp = xhci_readl(xhci, &xhci->cap_regs->hcs_params3);
 		buf[12] = HCS_U1_LATENCY(temp);
 		put_unaligned_le16(HCS_U2_LATENCY(temp), &buf[13]);
 
+		/* Indicate whether the host has LTM support. */
+		temp = xhci_readl(xhci, &xhci->cap_regs->hcc_params);
+		if (HCC_LTC(temp))
+			buf[8] |= USB_LTM_SUPPORT;
+
 		spin_unlock_irqrestore(&xhci->lock, flags);
 		return USB_DT_BOS_SIZE + USB_DT_USB_SS_CAP_SIZE;
 	case GetPortStatus:

include/linux/usb.h

@@ -561,7 +561,6 @@ struct usb_device {
 	struct usb3_lpm_parameters u1_params;
 	struct usb3_lpm_parameters u2_params;
 	unsigned lpm_disable_count;
-	unsigned hub_initiated_lpm_disable_count;
 };
 #define	to_usb_device(d) container_of(d, struct usb_device, dev)
 
@@ -634,6 +633,17 @@ extern void usb_enable_lpm(struct usb_device *udev);
 extern int usb_unlocked_disable_lpm(struct usb_device *udev);
 extern void usb_unlocked_enable_lpm(struct usb_device *udev);
 
+extern int usb_disable_ltm(struct usb_device *udev);
+extern void usb_enable_ltm(struct usb_device *udev);
+
+static inline bool usb_device_supports_ltm(struct usb_device *udev)
+{
+	if (udev->speed != USB_SPEED_SUPER || !udev->bos || !udev->bos->ss_cap)
+		return false;
+	return udev->bos->ss_cap->bmAttributes & USB_LTM_SUPPORT;
+}
+
+
 /*-------------------------------------------------------------------------*/
 
 /* for drivers using iso endpoints */