[PATCH] USB: EHCI and full-speed ISO-OUT

This is a minor update to the patch I sent out about a week ago.
The key change is to use the I/O watchdog while doing ISO streaming.
Bernd Porr reports that a VT8235 system needs that; it seems like
IDE activity can interfere with the delivery of USB IRQs.


EHCI periodic scheduling updates.

 - Initial version of full speed ISO transaction support.  This
   should handle OUT transactions, such as those for usb speakers.
   For now, it's controlled using an EXPERIMENTAL config option:

   * I've run into interesting differences in how different USB 2.0
     hub silicon (the transaction translators) handle some older
     audio devices.  Needs more investigation.

   * Interrupt transfer scheduling doesn't yet cope well with schedules
     where every slot already has activity.  For now, don't plug in
     devices like hubs, mice, or keyboards while EHCI is streaming.

 - Protect freelist for highspeed ITDs, using spinlock.  Could be
   an issue for some drivers.

 - Kick in the I/O watchdog timer (5 msec) for periodic transfers.
   In this case, IDE activity on a VT8235 lost the IRQs which should
   have kept the ISO stream active.  Queues shorter than 5 msec are
   not going to work on all USB hosts.

 - Simplified the ISO scheduler:  doesn't attempt to re-schedule
   after lossage, or to short-circuit scanning.  (Rescheduling will
   probably come back later ... for now, the "hard" error here is
   highlighting problems that need attention.)

drivers/usb/host/Kconfig

@@ -29,6 +29,15 @@ config USB_EHCI_HCD
 	  To compile this driver as a module, choose M here: the
 	  module will be called ehci-hcd.
 
+config USB_EHCI_SPLIT_ISO
+	bool "Full speed ISO transactions (EXPERIMENTAL)"
+	depends on USB_EHCI_HCD && EXPERIMENTAL
+	default n
+	---help---
+	  This code is new and hasn't been used with many different
+	  EHCI or USB 2.0 transaction translator implementations.
+	  It should work for ISO-OUT transfers, like audio.
+
 config USB_OHCI_HCD
 	tristate "OHCI HCD support"
 	depends on USB

drivers/usb/host/ehci-dbg.c

@@ -579,7 +579,11 @@ show_periodic (struct class_device *class_dev, char *buf)
 				break;
 			case Q_TYPE_SITD:
 				temp = scnprintf (next, size,
-					" sitd/%p", p.sitd);
+					" sitd%d-%04x/%p",
+					p.sitd->stream->interval,
+					le32_to_cpup (&p.sitd->hw_uframe)
+						& 0x0000ffff,
+					p.sitd);
 				tag = Q_NEXT_TYPE (p.sitd->hw_next);
 				p = p.sitd->sitd_next;
 				break;

drivers/usb/host/ehci-hcd.c

@@ -106,8 +106,6 @@ static const char	hcd_name [] = "ehci_hcd";
 #undef EHCI_VERBOSE_DEBUG
 #undef EHCI_URB_TRACE
 
-// #define have_split_iso
-
 #ifdef DEBUG
 #define EHCI_STATS
 #endif
@@ -676,6 +674,7 @@ static void ehci_work (struct ehci_hcd *ehci, struct pt_regs *regs)
 
 	/* the IO watchdog guards against hardware or driver bugs that
 	 * misplace IRQs, and should let us run completely without IRQs.
+	 * such lossage has been observed on both VT6202 and VT8235. 
 	 */
 	if ((ehci->async->qh_next.ptr != 0) || (ehci->periodic_sched != 0))
 		timer_action (ehci, TIMER_IO_WATCHDOG);
@@ -796,13 +795,8 @@ static int ehci_urb_enqueue (
 	case PIPE_ISOCHRONOUS:
 		if (urb->dev->speed == USB_SPEED_HIGH)
 			return itd_submit (ehci, urb, mem_flags);
-#ifdef have_split_iso
 		else
 			return sitd_submit (ehci, urb, mem_flags);
-#else
-		dbg ("no split iso support yet");
-		return -ENOSYS;
-#endif /* have_split_iso */
 	}
 }
 

drivers/usb/host/ehci.h

@@ -492,16 +492,16 @@ struct ehci_itd {
 /*
  * EHCI Specification 0.95 Section 3.4 
  * siTD, aka split-transaction isochronous Transfer Descriptor
- *       ... describe low/full speed iso xfers through TT in hubs
+ *       ... describe full speed iso xfers through TT in hubs
  * see Figure 3-5 "Split-transaction Isochronous Transaction Descriptor (siTD)
  */
 struct ehci_sitd {
 	/* first part defined by EHCI spec */
 	u32			hw_next;
 /* uses bit field macros above - see EHCI 0.95 Table 3-8 */
-	u32			hw_fullspeed_ep;	/* see EHCI table 3-9 */
-	u32			hw_uframe;		/* see EHCI table 3-10 */
-	u32			hw_results;		/* see EHCI table 3-11 */
+	u32			hw_fullspeed_ep;	/* EHCI table 3-9 */
+	u32			hw_uframe;		/* EHCI table 3-10 */
+	u32			hw_results;		/* EHCI table 3-11 */
 #define	SITD_IOC	(1 << 31)	/* interrupt on completion */
 #define	SITD_PAGE	(1 << 30)	/* buffer 0/1 */
 #define	SITD_LENGTH(x)	(0x3ff & ((x)>>16))
@@ -515,8 +515,8 @@ struct ehci_sitd {
 
 #define SITD_ACTIVE	__constant_cpu_to_le32(SITD_STS_ACTIVE)
 
-	u32			hw_buf [2];		/* see EHCI table 3-12 */
-	u32			hw_backpointer;		/* see EHCI table 3-13 */
+	u32			hw_buf [2];		/* EHCI table 3-12 */
+	u32			hw_backpointer;		/* EHCI table 3-13 */
 	u32			hw_buf_hi [2];		/* Appendix B */
 
 	/* the rest is HCD-private */
@@ -552,8 +552,6 @@ struct ehci_fstn {
 
 /*-------------------------------------------------------------------------*/
 
-#define SUBMIT_URB(urb,mem_flags) usb_submit_urb(urb,mem_flags)
-
 #ifndef DEBUG
 #define STUB_DEBUG_FILES
 #endif	/* DEBUG */