From: David Brownell <david-b@pacbell.net>
Date: Thu, 17 May 2007 19:21:19 +0000 (-0700)
Subject: USB: ehci refcounts work on ppc7448
X-Git-Tag: v2.6.23-rc1~1083^2~131
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9c033e810eef0aff6d4d3bf028aa1e583c074f93;p=linux-2.6

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 bdb29e6180..8816d09903 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 79ad2af5ef..6ef9d77577 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;