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, 17 insertions, 2 deletions

diff --git a/drivers/usb/core/hcd.h b/drivers/usb/core/hcd.h
index 79782a1c43f..d8b43aee581 100644
--- a/drivers/usb/core/hcd.h
+++ b/drivers/usb/core/hcd.h
@@ -111,6 +111,20 @@ struct usb_hcd {
 	u64			rsrc_len;	/* memory/io resource length */
 	unsigned		power_budget;	/* in mA, 0 = no limit */
 
+	/* bandwidth_mutex should be taken before adding or removing
+	 * any new bus bandwidth constraints:
+	 *   1. Before adding a configuration for a new device.
+	 *   2. Before removing the configuration to put the device into
+	 *      the addressed state.
+	 *   3. Before selecting a different configuration.
+	 *   4. Before selecting an alternate interface setting.
+	 *
+	 * bandwidth_mutex should be dropped after a successful control message
+	 * to the device, or resetting the bandwidth after a failed attempt.
+	 */
+	struct mutex		bandwidth_mutex;
+
+
 #define HCD_BUFFER_POOLS	4
 	struct dma_pool		*pool [HCD_BUFFER_POOLS];
 
@@ -290,9 +304,10 @@ extern void usb_hcd_disable_endpoint(struct usb_device *udev,
 extern void usb_hcd_reset_endpoint(struct usb_device *udev,
 		struct usb_host_endpoint *ep);
 extern void usb_hcd_synchronize_unlinks(struct usb_device *udev);
-extern int usb_hcd_check_bandwidth(struct usb_device *udev,
+extern int usb_hcd_alloc_bandwidth(struct usb_device *udev,
 		struct usb_host_config *new_config,
-		struct usb_interface *new_intf);
+		struct usb_host_interface *old_alt,
+		struct usb_host_interface *new_alt);
 extern int usb_hcd_get_frame_number(struct usb_device *udev);
 
 extern struct usb_hcd *usb_create_hcd(const struct hc_driver *driver,