[PATCH] USB: ehci: microframe handling fix

This patch has a one line oops fix, plus related cleanups.

 - The bugfix uses microframe scheduling data given to the hardware to
   test "is this a periodic QH", rather than testing for nonzero period.
   (Prevents an oops by providing the correct answer.)

 - The cleanup going along with the patch should make it clearer what's
   going on whenever those bitfields are accessed.

The bug came about when, around January, two new kinds of EHCI interrupt
scheduling operation were added, involving both the high speed (24 KBytes
per millisec) and low/full speed (1-64 bytes per millisec) microframe
scheduling.  A driver for the Edirol UA-1000 Audio Capture Unit ran into
the oops; it used one of the newly supported high speed modes.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 6 deletions

diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index 9af4f64532a9..b56f25864ed6 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -301,7 +301,7 @@ static int qh_link_periodic (struct ehci_hcd *ehci, struct ehci_qh *qh)
 
 	dev_dbg (&qh->dev->dev,
 		"link qh%d-%04x/%p start %d [%d/%d us]\n",
-		period, le32_to_cpup (&qh->hw_info2) & 0xffff,
+		period, le32_to_cpup (&qh->hw_info2) & (QH_CMASK | QH_SMASK),
 		qh, qh->start, qh->usecs, qh->c_usecs);
 
 	/* high bandwidth, or otherwise every microframe */
@@ -385,7 +385,8 @@ static void qh_unlink_periodic (struct ehci_hcd *ehci, struct ehci_qh *qh)
 
 	dev_dbg (&qh->dev->dev,
 		"unlink qh%d-%04x/%p start %d [%d/%d us]\n",
-		qh->period, le32_to_cpup (&qh->hw_info2) & 0xffff,
+		qh->period,
+		le32_to_cpup (&qh->hw_info2) & (QH_CMASK | QH_SMASK),
 		qh, qh->start, qh->usecs, qh->c_usecs);
 
 	/* qh->qh_next still "live" to HC */
@@ -411,7 +412,7 @@ static void intr_deschedule (struct ehci_hcd *ehci, struct ehci_qh *qh)
 	 * active high speed queues may need bigger delays...
 	 */
 	if (list_empty (&qh->qtd_list)
-			|| (__constant_cpu_to_le32 (0x0ff << 8)
+			|| (__constant_cpu_to_le32 (QH_CMASK)
 					& qh->hw_info2) != 0)
 		wait = 2;
 	else
@@ -533,7 +534,7 @@ static int qh_schedule (struct ehci_hcd *ehci, struct ehci_qh *qh)
 
 	/* reuse the previous schedule slots, if we can */
 	if (frame < qh->period) {
-		uframe = ffs (le32_to_cpup (&qh->hw_info2) & 0x00ff);
+		uframe = ffs (le32_to_cpup (&qh->hw_info2) & QH_SMASK);
 		status = check_intr_schedule (ehci, frame, --uframe,
 				qh, &c_mask);
 	} else {
@@ -569,10 +570,10 @@ static int qh_schedule (struct ehci_hcd *ehci, struct ehci_qh *qh)
 		qh->start = frame;
 
 		/* reset S-frame and (maybe) C-frame masks */
-		qh->hw_info2 &= __constant_cpu_to_le32 (~0xffff);
+		qh->hw_info2 &= __constant_cpu_to_le32(~(QH_CMASK | QH_SMASK));
 		qh->hw_info2 |= qh->period
 			? cpu_to_le32 (1 << uframe)
-			: __constant_cpu_to_le32 (0xff);
+			: __constant_cpu_to_le32 (QH_SMASK);
 		qh->hw_info2 |= c_mask;
 	} else
 		ehci_dbg (ehci, "reused qh %p schedule\n", qh);