USB: Check bandwidth when switching alt settings.

Make the USB core check the bandwidth when switching from one
interface alternate setting to another.  Also check the bandwidth
when resetting a configuration (so that alt setting 0 is used).  If
this check fails, the device's state is unchanged.  If the device
refuses the new alt setting, re-instate the old alt setting in the
host controller hardware.

If a USB device doesn't have an alternate interface setting 0, install
the first alt setting in its descriptors when a new configuration is
requested, or the device is reset.

Add a mutex per root hub to protect bandwidth operations:
adding/reseting/changing configurations, and changing alternate interface
settings.  We want to ensure that the xHCI host controller and the USB
device are set up for the same configurations and alternate settings.
There are two (possibly three) steps to do this:

 1. The host controller needs to check that bandwidth is available for a
    different setting, by issuing and waiting for a configure endpoint
    command.
 2. Once that returns successfully, a control message is sent to the
    device.
 3. If that fails, the host controller must be notified through another
    configure endpoint command.

The mutex is used to make these three operations seem atomic, to prevent
another driver from using more bandwidth for a different device while
we're in the middle of these operations.

While we're touching the bandwidth code, rename usb_hcd_check_bandwidth()
to usb_hcd_alloc_bandwidth().  This function does more than just check
that the bandwidth change won't exceed the bus bandwidth; it actually
changes the bandwidth configuration in the xHCI host controller.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 44 insertions, 12 deletions

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index fc235b0..6dac3b8 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -38,6 +38,7 @@
 #include <asm/unaligned.h>
 #include <linux/platform_device.h>
 #include <linux/workqueue.h>
+#include <linux/mutex.h>
 
 #include <linux/usb.h>
 
@@ -1595,15 +1596,29 @@ rescan:
 	}
 }
 
-/* Check whether a new configuration or alt setting for an interface
- * will exceed the bandwidth for the bus (or the host controller resources).
- * Only pass in a non-NULL config or interface, not both!
- * Passing NULL for both new_config and new_intf means the device will be
- * de-configured by issuing a set configuration 0 command.
+/**
+ * Check whether a new bandwidth setting exceeds the bus bandwidth.
+ * @new_config: new configuration to install
+ * @cur_alt: the current alternate interface setting
+ * @new_alt: alternate interface setting that is being installed
+ *
+ * To change configurations, pass in the new configuration in new_config,
+ * and pass NULL for cur_alt and new_alt.
+ *
+ * To reset a device's configuration (put the device in the ADDRESSED state),
+ * pass in NULL for new_config, cur_alt, and new_alt.
+ *
+ * To change alternate interface settings, pass in NULL for new_config,
+ * pass in the current alternate interface setting in cur_alt,
+ * and pass in the new alternate interface setting in new_alt.
+ *
+ * Returns an error if the requested bandwidth change exceeds the
+ * bus bandwidth or host controller internal resources.
  */
-int usb_hcd_check_bandwidth(struct usb_device *udev,
+int usb_hcd_alloc_bandwidth(struct usb_device *udev,
 		struct usb_host_config *new_config,
-		struct usb_interface *new_intf)
+		struct usb_host_interface *cur_alt,
+		struct usb_host_interface *new_alt)
 {
 	int num_intfs, i, j;
 	struct usb_host_interface *alt = NULL;
@@ -1616,7 +1631,7 @@ int usb_hcd_check_bandwidth(struct usb_device *udev,
 		return 0;
 
 	/* Configuration is being removed - set configuration 0 */
-	if (!new_config && !new_intf) {
+	if (!new_config && !cur_alt) {
 		for (i = 1; i < 16; ++i) {
 			ep = udev->ep_out[i];
 			if (ep)
@@ -1655,10 +1670,10 @@ int usb_hcd_check_bandwidth(struct usb_device *udev,
 		for (i = 0; i < num_intfs; ++i) {
 			/* Set up endpoints for alternate interface setting 0 */
 			alt = usb_find_alt_setting(new_config, i, 0);
-			if (!alt) {
-				printk(KERN_DEBUG "Did not find alt setting 0 for intf %d\n", i);
-				continue;
-			}
+			if (!alt)
+				/* No alt setting 0? Pick the first setting. */
+				alt = &new_config->intf_cache[i]->altsetting[0];
+
 			for (j = 0; j < alt->desc.bNumEndpoints; j++) {
 				ret = hcd->driver->add_endpoint(hcd, udev, &alt->endpoint[j]);
 				if (ret < 0)
@@ -1666,6 +1681,22 @@ int usb_hcd_check_bandwidth(struct usb_device *udev,
 			}
 		}
 	}
+	if (cur_alt && new_alt) {
+		/* Drop all the endpoints in the current alt setting */
+		for (i = 0; i < cur_alt->desc.bNumEndpoints; i++) {
+			ret = hcd->driver->drop_endpoint(hcd, udev,
+					&cur_alt->endpoint[i]);
+			if (ret < 0)
+				goto reset;
+		}
+		/* Add all the endpoints in the new alt setting */
+		for (i = 0; i < new_alt->desc.bNumEndpoints; i++) {
+			ret = hcd->driver->add_endpoint(hcd, udev,
+					&new_alt->endpoint[i]);
+			if (ret < 0)
+				goto reset;
+		}
+	}
 	ret = hcd->driver->check_bandwidth(hcd, udev);
 reset:
 	if (ret < 0)
@@ -1982,6 +2013,7 @@ struct usb_hcd *usb_create_hcd (const struct hc_driver *driver,
 #ifdef CONFIG_PM
 	INIT_WORK(&hcd->wakeup_work, hcd_resume_work);
 #endif
+	mutex_init(&hcd->bandwidth_mutex);
 
 	hcd->driver = driver;
 	hcd->product_desc = (driver->product_desc) ? driver->product_desc :