From 7efb6dbd0d825899955fd4035504823bb5c1124c Mon Sep 17 00:00:00 2001
From: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Date: Tue, 04 Mar 2014 22:28:16 +0000
Subject: Revert "xhci 1.0: Limit arbitrarily-aligned scatter gather."

This reverts commit 247bf557273dd775505fb9240d2d152f4f20d304, since it
causes USB 3.0 mass storage devices to fail on xHCI 1.0 hosts.

The block layer may submit scatter-gather lists with entries that
are multiples of 512-byte blocks.  That's fine for USB 2.0 devices,
where the bulk endpoint max packet size is 512 bytes.  But USB 3.0
devices have bulk endpoints with a 1024 byte max packet size.

That means when the block layer submits a scatter-gather list with one
entry that includes, say, three 512-byte blocks, this code will reject
the URB if it's submitted to a USB 3.0 bulk endpoint:

int usb_submit_urb(struct urb *urb, gfp_t mem_flags)
{
...
        max = usb_endpoint_maxp(&ep->desc);
...
        } else if (urb->num_sgs && !urb->dev->bus->no_sg_constraint &&
                        dev->speed != USB_SPEED_WIRELESS) {
                struct scatterlist *sg;
                int i;

                for_each_sg(urb->sg, sg, urb->num_sgs - 1, i)
                        if (sg->length % max)
                                return -EINVAL;
        }

This results in failures with USB 3.0 drives.  For me, a failure to
auto-mount the device.  For others, a read or write SCSI command
failure.

This commit was put in place so that we could get scatter-gather support
for the ASIX USB ethernet adapter on non-1.0 hosts.  It was a quick fix
until we implemented TD fragments properly in the driver.  Since it
breaks USB 3.0 mass storage, we need to revert it, and revert
scatter-gather support for the ASIX devices.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: stable@vger.kernel.org # 3.12
---
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 652be21..8fe4e12 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -4762,6 +4762,9 @@ int xhci_gen_setup(struct usb_hcd *hcd, xhci_get_quirks_t get_quirks)
 	/* Accept arbitrarily long scatter-gather lists */
 	hcd->self.sg_tablesize = ~0;
 
+	/* support to build packet from discontinuous buffers */
+	hcd->self.no_sg_constraint = 1;
+
 	/* XHCI controllers don't stop the ep queue on short packets :| */
 	hcd->self.no_stop_on_short = 1;
 
@@ -4786,14 +4789,6 @@ int xhci_gen_setup(struct usb_hcd *hcd, xhci_get_quirks_t get_quirks)
 		/* xHCI private pointer was set in xhci_pci_probe for the second
 		 * registered roothub.
 		 */
-		xhci = hcd_to_xhci(hcd);
-		/*
-		 * Support arbitrarily aligned sg-list entries on hosts without
-		 * TD fragment rules (which are currently unsupported).
-		 */
-		if (xhci->hci_version < 0x100)
-			hcd->self.no_sg_constraint = 1;
-
 		return 0;
 	}
 
@@ -4822,9 +4817,6 @@ int xhci_gen_setup(struct usb_hcd *hcd, xhci_get_quirks_t get_quirks)
 	if (xhci->hci_version > 0x96)
 		xhci->quirks |= XHCI_SPURIOUS_SUCCESS;
 
-	if (xhci->hci_version < 0x100)
-		hcd->self.no_sg_constraint = 1;
-
 	/* Make sure the HC is halted. */
 	retval = xhci_halt(xhci);
 	if (retval)
--
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