USB: ehci refcounts work on ppc7448

Remove atomic operations on the reference counter for EHCI queue heads.
On various platforms (including ppc7448), atomic operations are unusable
with dma-coherent memory.

Signed-off-by: Steven J. Hill <sjhill1@rockwellcollins.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 14 insertions, 6 deletions

diff --git a/drivers/usb/host/ehci-mem.c b/drivers/usb/host/ehci-mem.c
index bdb29e618058..8816d09903d0 100644
--- a/drivers/usb/host/ehci-mem.c
+++ b/drivers/usb/host/ehci-mem.c
@@ -64,9 +64,8 @@ static inline void ehci_qtd_free (struct ehci_hcd *ehci, struct ehci_qtd *qtd)
 }
 
 
-static void qh_destroy (struct kref *kref)
+static void qh_destroy(struct ehci_qh *qh)
 {
-        struct ehci_qh *qh = container_of(kref, struct ehci_qh, kref);
         struct ehci_hcd *ehci = qh->ehci;
 
         /* clean qtds first, and know this is not linked */
@@ -90,7 +89,7 @@ static struct ehci_qh *ehci_qh_alloc (struct ehci_hcd *ehci, gfp_t flags)
                 return qh;
 
         memset (qh, 0, sizeof *qh);
-        kref_init(&qh->kref);
+        qh->refcount = 1;
         qh->ehci = ehci;
         qh->qh_dma = dma;
         // INIT_LIST_HEAD (&qh->qh_list);
@@ -112,13 +111,15 @@ static struct ehci_qh *ehci_qh_alloc (struct ehci_hcd *ehci, gfp_t flags)
 /* to share a qh (cpu threads, or hc) */
 static inline struct ehci_qh *qh_get (struct ehci_qh *qh)
 {
-        kref_get(&qh->kref);
+        WARN_ON(!qh->refcount);
+        qh->refcount++;
         return qh;
 }
 
 static inline void qh_put (struct ehci_qh *qh)
 {
-        kref_put(&qh->kref, qh_destroy);
+        if (!--qh->refcount)
+                qh_destroy(qh);
 }
 
 /*-------------------------------------------------------------------------*/
diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h
index 79ad2af5ef6a..6ef9d775775b 100644
--- a/drivers/usb/host/ehci.h
+++ b/drivers/usb/host/ehci.h
@@ -457,7 +457,14 @@ struct ehci_qh {
         struct ehci_qh          *reclaim;       /* next to reclaim */
 
         struct ehci_hcd         *ehci;
-        struct kref             kref;
+
+        /*
+         * Do NOT use atomic operations for QH refcounting. On some CPUs
+         * (PPC7448 for example), atomic operations cannot be performed on
+         * memory that is cache-inhibited (i.e. being used for DMA).
+         * Spinlocks are used to protect all QH fields.
+         */
+        u32                     refcount;
         unsigned                stamp;
 
         u8                      qh_state;