Improve the realtime properties of USB transfers for embedded systems

like RPI-B and RPI-2.

Description of problem:
USB transfers can process data in their callbacks sometimes causing
unacceptable latency for other USB transfers. Separate BULK completion
callbacks from CONTROL, INTERRUPT and ISOCHRONOUS callbacks, and give
BULK completion callbacks lesser execution priority than the
others. This way USB audio won't be interfered by heavy USB ethernet
usage for example.

Further serve USB transfer completion in a round robin fashion,
instead of only serving the most CPU hungry. This has been done by
adding a third flag to USB transfer queue structure which keeps track
of looping callbacks. The "command" callback function then decides
what to do when looping.

MFC after:		2 weeks

1 files changed, 42 insertions, 16 deletions

diff --git a/sys/dev/usb/usb_transfer.c b/sys/dev/usb/usb_transfer.c
index 56507905e14e..0e8f0ab0ee0d 100644
--- a/sys/dev/usb/usb_transfer.c
+++ b/sys/dev/usb/usb_transfer.c
@@ -872,6 +872,19 @@ done:
 	}
 }
 
+static uint8_t
+usbd_transfer_setup_has_bulk(const struct usb_config *setup_start,
+    uint16_t n_setup)
+{
+	while (n_setup--) {
+		uint8_t type = setup_start[n_setup].type;
+		if (type == UE_BULK || type == UE_BULK_INTR ||
+		    type == UE_TYPE_ANY)
+			return (1);
+	}
+	return (0);
+}
+
 /*------------------------------------------------------------------------*
  *	usbd_transfer_setup - setup an array of USB transfers
  *
@@ -1013,9 +1026,12 @@ usbd_transfer_setup(struct usb_device *udev,
 			else if (xfer_mtx == &Giant)
 				info->done_p =
 				    USB_BUS_GIANT_PROC(udev->bus);
+			else if (usbd_transfer_setup_has_bulk(setup_start, n_setup))
+				info->done_p =
+				    USB_BUS_NON_GIANT_BULK_PROC(udev->bus);
 			else
 				info->done_p =
-				    USB_BUS_NON_GIANT_PROC(udev->bus);
+				    USB_BUS_NON_GIANT_ISOC_PROC(udev->bus);
 		}
 		/* reset sizes */
 
@@ -2280,10 +2296,8 @@ usbd_callback_ss_done_defer(struct usb_xfer *xfer)
 	         * will have a Lock Order Reversal, LOR, if we try to
 	         * proceed !
 	         */
-		if (usb_proc_msignal(info->done_p,
-		    &info->done_m[0], &info->done_m[1])) {
-			/* ignore */
-		}
+		(void) usb_proc_msignal(info->done_p,
+		    &info->done_m[0], &info->done_m[1]);
 	} else {
 		/* clear second recurse flag */
 		pq->recurse_2 = 0;
@@ -2307,23 +2321,26 @@ usbd_callback_wrapper(struct usb_xfer_queue *pq)
 	struct usb_xfer_root *info = xfer->xroot;
 
 	USB_BUS_LOCK_ASSERT(info->bus, MA_OWNED);
-	if (!mtx_owned(info->xfer_mtx) && !SCHEDULER_STOPPED()) {
+	if ((pq->recurse_3 != 0 || mtx_owned(info->xfer_mtx) == 0) &&
+	    SCHEDULER_STOPPED() == 0) {
 		/*
 	       	 * Cases that end up here:
 		 *
 		 * 5) HW interrupt done callback or other source.
+		 * 6) HW completed transfer during callback
 		 */
-		DPRINTFN(3, "case 5\n");
+		DPRINTFN(3, "case 5 and 6\n");
 
 		/*
 	         * We have to postpone the callback due to the fact we
 	         * will have a Lock Order Reversal, LOR, if we try to
-	         * proceed !
+	         * proceed!
+		 *
+		 * Postponing the callback also ensures that other USB
+		 * transfer queues get a chance.
 	         */
-		if (usb_proc_msignal(info->done_p,
-		    &info->done_m[0], &info->done_m[1])) {
-			/* ignore */
-		}
+		(void) usb_proc_msignal(info->done_p,
+		    &info->done_m[0], &info->done_m[1]);
 		return;
 	}
 	/*
@@ -2694,7 +2711,7 @@ usbd_pipe_start(struct usb_xfer_queue *pq)
 			} else if (udev->ctrl_xfer[1]) {
 				info = udev->ctrl_xfer[1]->xroot;
 				usb_proc_msignal(
-				    USB_BUS_NON_GIANT_PROC(info->bus),
+				    USB_BUS_CS_PROC(info->bus),
 				    &udev->cs_msg[0], &udev->cs_msg[1]);
 			} else {
 				/* should not happen */
@@ -3019,9 +3036,11 @@ usb_command_wrapper(struct usb_xfer_queue *pq, struct usb_xfer *xfer)
 
 	if (!pq->recurse_1) {
 
-		do {
+		/* clear third recurse flag */
+		pq->recurse_3 = 0;
 
-			/* set both recurse flags */
+		do {
+			/* set two first recurse flags */
 			pq->recurse_1 = 1;
 			pq->recurse_2 = 1;
 
@@ -3040,6 +3059,12 @@ usb_command_wrapper(struct usb_xfer_queue *pq, struct usb_xfer *xfer)
 			(pq->command) (pq);
 			DPRINTFN(6, "cb %p (leave)\n", pq->curr);
 
+			/*
+			 * Set third recurse flag to indicate
+			 * recursion happened:
+			 */
+			pq->recurse_3 = 1;
+
 		} while (!pq->recurse_2);
 
 		/* clear first recurse flag */
@@ -3315,7 +3340,8 @@ usbd_transfer_poll(struct usb_xfer **ppxfer, uint16_t max)
 		USB_BUS_CONTROL_XFER_PROC(udev->bus)->up_msleep = 0;
 		USB_BUS_EXPLORE_PROC(udev->bus)->up_msleep = 0;
 		USB_BUS_GIANT_PROC(udev->bus)->up_msleep = 0;
-		USB_BUS_NON_GIANT_PROC(udev->bus)->up_msleep = 0;
+		USB_BUS_NON_GIANT_ISOC_PROC(udev->bus)->up_msleep = 0;
+		USB_BUS_NON_GIANT_BULK_PROC(udev->bus)->up_msleep = 0;
 
 		/* poll USB hardware */
 		(udev->bus->methods->xfer_poll) (udev->bus);