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>

diff --git a/drivers/usb/host/ehci-mem.c b/drivers/usb/host/ehci-mem.c
index bdb29e6..8816d09 100644 (file)
--- 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 79ad2af..6ef9d77 100644 (file)
--- 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;