usb: xhci: change enumeration scheme to 'new scheme' by default

Change the default enumeration scheme for xhci attached non-SuperSpeed
devices from:

   Reset
   SetAddress [xhci address-device BSR = 0]
   GetDescriptor(8)
   GetDescriptor(18)

...to:

   Reset
   [xhci address-device BSR = 1]
   GetDescriptor(64)
   Reset
   SetAddress [xhci address-device BSR = 0]
   GetDescriptor(18)

...as some devices misbehave when encountering a SetAddress command
prior to GetDescriptor.  There are known legacy devices that require
this scheme, but testing has found at least one USB3 device that fails
enumeration when presented with this ordering.  For now, follow the ehci
case and enable 'new scheme' by default for non-SuperSpeed devices.

To support this enumeration scheme on xhci the AddressDevice operation
needs to be performed twice.  The first instance of the command enables
the HC's device and slot context info for the device, but omits sending
the device a SetAddress command (BSR == block set address request).
Then, after GetDescriptor completes, follow up with the full
AddressDevice+SetAddress operation.

As mentioned before, this ordering of events with USB3 devices causes an
extra state transition to be exposed to xhci.  Previously USB3 devices
would transition directly from 'enabled' to 'addressed' and never need
to underrun responses to 'get descriptor'. We do see the 64-byte
descriptor fetch the correct data, but the following 18-byte descriptor
read after the reset gets:

bLength            = 0
bDescriptorType    = 0
bcdUSB             = 0
bDeviceClass       = 0
bDeviceSubClass    = 0
bDeviceProtocol    = 0
bMaxPacketSize0    = 9

instead of:

bLength            = 12
bDescriptorType    = 1
bcdUSB             = 300
bDeviceClass       = 0
bDeviceSubClass    = 0
bDeviceProtocol    = 0
bMaxPacketSize0    = 9

which results in the discovery process looping until falling back to
'old scheme' enumeration.

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: David Moore <david.moore@gmail.com>
Suggested-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

1 files changed, 43 insertions, 3 deletions

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 32e1035d4f59..6a11eff74d3c 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -2498,6 +2498,21 @@ static unsigned hub_is_wusb(struct usb_hub *hub)
 #define HUB_LONG_RESET_TIME     200
 #define HUB_RESET_TIMEOUT       800
 
+/*
+ * "New scheme" enumeration causes an extra state transition to be
+ * exposed to an xhci host and causes USB3 devices to receive control
+ * commands in the default state.  This has been seen to cause
+ * enumeration failures, so disable this enumeration scheme for USB3
+ * devices.
+ */
+static bool use_new_scheme(struct usb_device *udev, int retry)
+{
+        if (udev->speed == USB_SPEED_SUPER)
+                return false;
+
+        return USE_NEW_SCHEME(retry);
+}
+
 static int hub_port_reset(struct usb_hub *hub, int port1,
                         struct usb_device *udev, unsigned int delay, bool warm);
 
@@ -3956,6 +3971,20 @@ static void hub_set_initial_usb2_lpm_policy(struct usb_device *udev)
         }
 }
 
+static int hub_enable_device(struct usb_device *udev)
+{
+        struct usb_hcd *hcd = bus_to_hcd(udev->bus);
+
+        if (!hcd->driver->enable_device)
+                return 0;
+        if (udev->state == USB_STATE_ADDRESS)
+                return 0;
+        if (udev->state != USB_STATE_DEFAULT)
+                return -EINVAL;
+
+        return hcd->driver->enable_device(hcd, udev);
+}
+
 /* Reset device, (re)assign address, get device descriptor.
  * Device connection must be stable, no more debouncing needed.
  * Returns device in USB_STATE_ADDRESS, except on error.
@@ -4068,7 +4097,7 @@ hub_port_init (struct usb_hub *hub, struct usb_device *udev, int port1,
          * this area, and this is how Linux has done it for ages.
          * Change it cautiously.
          *
-         * NOTE:  If USE_NEW_SCHEME() is true we will start by issuing
+         * NOTE:  If use_new_scheme() is true we will start by issuing
          * a 64-byte GET_DESCRIPTOR request.  This is what Windows does,
          * so it may help with some non-standards-compliant devices.
          * Otherwise we start with SET_ADDRESS and then try to read the
@@ -4076,10 +4105,17 @@ hub_port_init (struct usb_hub *hub, struct usb_device *udev, int port1,
          * value.
          */
         for (i = 0; i < GET_DESCRIPTOR_TRIES; (++i, msleep(100))) {
-                if (USE_NEW_SCHEME(retry_counter) && !(hcd->driver->flags & HCD_USB3)) {
+                bool did_new_scheme = false;
+
+                if (use_new_scheme(udev, retry_counter)) {
                         struct usb_device_descriptor *buf;
                         int r = 0;
 
+                        did_new_scheme = true;
+                        retval = hub_enable_device(udev);
+                        if (retval < 0)
+                                goto fail;
+
 #define GET_DESCRIPTOR_BUFSIZE  64
                         buf = kmalloc(GET_DESCRIPTOR_BUFSIZE, GFP_NOIO);
                         if (!buf) {
@@ -4168,7 +4204,11 @@ hub_port_init (struct usb_hub *hub, struct usb_device *udev, int port1,
                          *  - read ep0 maxpacket even for high and low speed,
                          */
                         msleep(10);
-                        if (USE_NEW_SCHEME(retry_counter) && !(hcd->driver->flags & HCD_USB3))
+                        /* use_new_scheme() checks the speed which may have
+                         * changed since the initial look so we cache the result
+                         * in did_new_scheme
+                         */
+                        if (did_new_scheme)
                                 break;
                 }