USB: make urb scatter-gather support more generic

The WHCI HCD will also support urbs with scatter-gather lists.  Add a
usb_bus field to indicated how many sg list elements are supported by
the HCD.  Use this to decide whether to pass the scatter-list to the HCD
or not.

Make the usb-storage driver use this new field.

Signed-off-by: David Vrabel <david.vrabel@csr.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: Matthew Dharm <mdharm-usb@one-eyed-alien.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

4 files changed, 14 insertions, 7 deletions

diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index e80f1af438c8..8d874cad6581 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -393,13 +393,7 @@ int usb_sg_init(struct usb_sg_request *io, struct usb_device *dev,
         if (io->entries <= 0)
                 return io->entries;
 
-        /* If we're running on an xHCI host controller, queue the whole scatter
-         * gather list with one call to urb_enqueue().  This is only for bulk,
-         * as that endpoint type does not care how the data gets broken up
-         * across frames.
-         */
-        if (usb_pipebulk(pipe) &&
-                        bus_to_hcd(dev->bus)->driver->flags & HCD_USB3) {
+        if (dev->bus->sg_tablesize > 0) {
                 io->urbs = kmalloc(sizeof *io->urbs, mem_flags);
                 use_sg = true;
         } else {
diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
index 06595ec27bb7..e097008d6fb1 100644
--- a/drivers/usb/host/xhci-pci.c
+++ b/drivers/usb/host/xhci-pci.c
@@ -54,6 +54,8 @@ static int xhci_pci_setup(struct usb_hcd *hcd)
         struct pci_dev          *pdev = to_pci_dev(hcd->self.controller);
         int                     retval;
 
+        hcd->self.sg_tablesize = TRBS_PER_SEGMENT - 1;
+
         xhci->cap_regs = hcd->regs;
         xhci->op_regs = hcd->regs +
                 HC_LENGTH(xhci_readl(xhci, &xhci->cap_regs->hc_capbase));
diff --git a/drivers/usb/storage/usb.c b/drivers/usb/storage/usb.c
index 01e43a13a6bf..1599d86154c4 100644
--- a/drivers/usb/storage/usb.c
+++ b/drivers/usb/storage/usb.c
@@ -843,6 +843,15 @@ static int usb_stor_scan_thread(void * __us)
         complete_and_exit(&us->scanning_done, 0);
 }
 
+static unsigned int usb_stor_sg_tablesize(struct usb_interface *intf)
+{
+        struct usb_device *usb_dev = interface_to_usbdev(intf);
+
+        if (usb_dev->bus->sg_tablesize) {
+                return usb_dev->bus->sg_tablesize;
+        }
+        return SG_ALL;
+}
 
 /* First part of general USB mass-storage probing */
 int usb_stor_probe1(struct us_data **pus,
@@ -871,6 +880,7 @@ int usb_stor_probe1(struct us_data **pus,
          * Allow 16-byte CDBs and thus > 2TB
          */
         host->max_cmd_len = 16;
+        host->sg_tablesize = usb_stor_sg_tablesize(intf);
         *pus = us = host_to_us(host);
         memset(us, 0, sizeof(struct us_data));
         mutex_init(&(us->dev_mutex));
diff --git a/include/linux/usb.h b/include/linux/usb.h
index a34fa89f1474..6e91ee4f5b81 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -331,6 +331,7 @@ struct usb_bus {
         u8 otg_port;                    /* 0, or number of OTG/HNP port */
         unsigned is_b_host:1;           /* true during some HNP roleswitches */
         unsigned b_hnp_enable:1;        /* OTG: did A-Host enable HNP? */
+        unsigned sg_tablesize;          /* 0 or largest number of sg list entries */
 
         int devnum_next;                /* Next open device number in
                                          * round-robin allocation */