Revert "xhci: Set scatter-gather limit to avoid failed block writes."

This reverts commit f2d9b99.

We are ripping out commit 35773da "usb:
xhci: Link TRB must not occur within a USB payload burst" because it's a
hack that caused regressions in the usb-storage and userspace USB
drivers that use usbfs and libusb.  This commit attempted to fix the
issues with that patch.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: stable@vger.kernel.org #3.12

drivers/usb/host/xhci.c

@@ -4730,8 +4730,8 @@ int xhci_gen_setup(struct usb_hcd *hcd, xhci_get_quirks_t get_quirks)
 	struct device		*dev = hcd->self.controller;
 	int			retval;
 
-	/* Limit the block layer scatter-gather lists to half a segment. */
-	hcd->self.sg_tablesize = TRBS_PER_SEGMENT / 2;
+	/* Accept arbitrarily long scatter-gather lists */
+	hcd->self.sg_tablesize = ~0;
 
 	/* XHCI controllers don't stop the ep queue on short packets :| */
 	hcd->self.no_stop_on_short = 1;

drivers/usb/host/xhci.h

@@ -1268,7 +1268,7 @@ union xhci_trb {
  * since the command ring is 64-byte aligned.
  * It must also be greater than 16.
  */
-#define TRBS_PER_SEGMENT	256
+#define TRBS_PER_SEGMENT	64
 /* Allow two commands + a link TRB, along with any reserved command TRBs */
 #define MAX_RSVD_CMD_TRBS	(TRBS_PER_SEGMENT - 3)
 #define TRB_SEGMENT_SIZE	(TRBS_PER_SEGMENT*16)