staging: dwc2: add microframe scheduler from downstream Pi kernel

The transfer scheduler in the dwc2 driver is pretty basic, not to
mention buggy. It works fairly well with just a couple of devices
plugged in, but if you add, say, multiple devices with periodic
endpoints, the scheduler breaks down and can't even enumerate all
the devices.

To improve this, import the "microframe scheduler" patch from the
driver in the downstream Raspberry Pi kernel, which is based on
the Synopsys vendor driver. The original patch came from Denx
(http://git.denx.de/?p=linux-denx.git) and was commited to the
raspberrypi.org git tree by "popcornmix" (Dom Cobley).

I have added a driver parameter for this, enabled by default, in
case anyone has problems with it and needs to disable it. I don't
think we should add a DT binding for that, though, since I plan
to remove the option once any bugs are fixed.

[raspberrypi.org patch from Dom Cobley]
Signed-off-by: Dom Cobley <popcornmix@gmail.com>
[adapted to dwc2 driver by Paul Zimmerman]
Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 186 insertions, 13 deletions

diff --git a/drivers/staging/dwc2/hcd_queue.c b/drivers/staging/dwc2/hcd_queue.c
index c09b2db2c89a..f200f1f6e1c6 100644
--- a/drivers/staging/dwc2/hcd_queue.c
+++ b/drivers/staging/dwc2/hcd_queue.c
@@ -324,6 +324,146 @@ static int dwc2_check_periodic_bandwidth(struct dwc2_hsotg *hsotg,
 }
 
 /**
+ * Microframe scheduler
+ * track the total use in hsotg->frame_usecs
+ * keep each qh use in qh->frame_usecs
+ * when surrendering the qh then donate the time back
+ */
+static const unsigned short max_uframe_usecs[] = {
+	100, 100, 100, 100, 100, 100, 30, 0
+};
+
+void dwc2_hcd_init_usecs(struct dwc2_hsotg *hsotg)
+{
+	int i;
+
+	for (i = 0; i < 8; i++)
+		hsotg->frame_usecs[i] = max_uframe_usecs[i];
+}
+
+static int dwc2_find_single_uframe(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
+{
+	unsigned short utime = qh->usecs;
+	int done = 0;
+	int i = 0;
+	int ret = -1;
+
+	while (!done) {
+		/* At the start hsotg->frame_usecs[i] = max_uframe_usecs[i] */
+		if (utime <= hsotg->frame_usecs[i]) {
+			hsotg->frame_usecs[i] -= utime;
+			qh->frame_usecs[i] += utime;
+			ret = i;
+			done = 1;
+		} else {
+			i++;
+			if (i == 8)
+				done = 1;
+		}
+	}
+
+	return ret;
+}
+
+/*
+ * use this for FS apps that can span multiple uframes
+ */
+static int dwc2_find_multi_uframe(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
+{
+	unsigned short utime = qh->usecs;
+	unsigned short xtime;
+	int t_left = utime;
+	int done = 0;
+	int i = 0;
+	int j;
+	int ret = -1;
+
+	while (!done) {
+		if (hsotg->frame_usecs[i] <= 0) {
+			i++;
+			if (i == 8) {
+				ret = -1;
+				done = 1;
+			}
+			continue;
+		}
+
+		/*
+		 * we need n consecutive slots so use j as a start slot
+		 * j plus j+1 must be enough time (for now)
+		 */
+		xtime = hsotg->frame_usecs[i];
+		for (j = i + 1; j < 8; j++) {
+			/*
+			 * if we add this frame remaining time to xtime we may
+			 * be OK, if not we need to test j for a complete frame
+			 */
+			if (xtime + hsotg->frame_usecs[j] < utime) {
+				if (hsotg->frame_usecs[j] <
+							max_uframe_usecs[j]) {
+					ret = -1;
+					break;
+				}
+			}
+			if (xtime >= utime) {
+				ret = i;
+				break;
+			}
+			/* add the frame time to x time */
+			xtime += hsotg->frame_usecs[j];
+			/* we must have a fully available next frame or break */
+			if (xtime < utime &&
+			   hsotg->frame_usecs[j] == max_uframe_usecs[j]) {
+				ret = -1;
+				break;
+			}
+		}
+		if (ret >= 0) {
+			t_left = utime;
+			for (j = i; t_left > 0 && j < 8; j++) {
+				t_left -= hsotg->frame_usecs[j];
+				if (t_left <= 0) {
+					qh->frame_usecs[j] +=
+						hsotg->frame_usecs[j] + t_left;
+					hsotg->frame_usecs[j] = -t_left;
+					ret = i;
+					done = 1;
+				} else {
+					qh->frame_usecs[j] +=
+						hsotg->frame_usecs[j];
+					hsotg->frame_usecs[j] = 0;
+				}
+			}
+		} else {
+			i++;
+			if (i == 8) {
+				ret = -1;
+				done = 1;
+			}
+		}
+	}
+
+	return ret;
+}
+
+static int dwc2_find_uframe(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
+{
+	int ret;
+
+	if (qh->dev_speed == USB_SPEED_HIGH) {
+		/* if this is a hs transaction we need a full frame */
+		ret = dwc2_find_single_uframe(hsotg, qh);
+	} else {
+		/*
+		 * if this is a fs transaction we may need a sequence
+		 * of frames
+		 */
+		ret = dwc2_find_multi_uframe(hsotg, qh);
+	}
+	return ret;
+}
+
+/**
  * dwc2_check_max_xfer_size() - Checks that the max transfer size allowed in a
  * host channel is large enough to handle the maximum data transfer in a single
  * (micro)frame for a periodic transfer
@@ -367,15 +507,35 @@ static int dwc2_schedule_periodic(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
 {
 	int status;
 
-	status = dwc2_periodic_channel_available(hsotg);
-	if (status) {
-		dev_dbg(hsotg->dev,
-			"%s: No host channel available for periodic transfer\n",
-			__func__);
-		return status;
+	if (hsotg->core_params->uframe_sched > 0) {
+		int frame = -1;
+
+		status = dwc2_find_uframe(hsotg, qh);
+		if (status == 0)
+			frame = 7;
+		else if (status > 0)
+			frame = status - 1;
+
+		/* Set the new frame up */
+		if (frame > -1) {
+			qh->sched_frame &= ~0x7;
+			qh->sched_frame |= (frame & 7);
+		}
+
+		if (status != -1)
+			status = 0;
+	} else {
+		status = dwc2_periodic_channel_available(hsotg);
+		if (status) {
+			dev_info(hsotg->dev,
+				 "%s: No host channel available for periodic transfer\n",
+				 __func__);
+			return status;
+		}
+
+		status = dwc2_check_periodic_bandwidth(hsotg, qh);
 	}
 
-	status = dwc2_check_periodic_bandwidth(hsotg, qh);
 	if (status) {
 		dev_dbg(hsotg->dev,
 			"%s: Insufficient periodic bandwidth for periodic transfer\n",
@@ -399,8 +559,9 @@ static int dwc2_schedule_periodic(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
 		list_add_tail(&qh->qh_list_entry,
 			      &hsotg->periodic_sched_inactive);
 
-	/* Reserve periodic channel */
-	hsotg->periodic_channels++;
+	if (hsotg->core_params->uframe_sched <= 0)
+		/* Reserve periodic channel */
+		hsotg->periodic_channels++;
 
 	/* Update claimed usecs per (micro)frame */
 	hsotg->periodic_usecs += qh->usecs;
@@ -418,13 +579,22 @@ static int dwc2_schedule_periodic(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
 static void dwc2_deschedule_periodic(struct dwc2_hsotg *hsotg,
 				     struct dwc2_qh *qh)
 {
-	list_del_init(&qh->qh_list_entry);
+	int i;
 
-	/* Release periodic channel reservation */
-	hsotg->periodic_channels--;
+	list_del_init(&qh->qh_list_entry);
 
 	/* Update claimed usecs per (micro)frame */
 	hsotg->periodic_usecs -= qh->usecs;
+
+	if (hsotg->core_params->uframe_sched > 0) {
+		for (i = 0; i < 8; i++) {
+			hsotg->frame_usecs[i] += qh->frame_usecs[i];
+			qh->frame_usecs[i] = 0;
+		}
+	} else {
+		/* Release periodic channel reservation */
+		hsotg->periodic_channels--;
+	}
 }
 
 /**
@@ -581,7 +751,10 @@ void dwc2_hcd_qh_deactivate(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh,
 			 * Remove from periodic_sched_queued and move to
 			 * appropriate queue
 			 */
-			if (qh->sched_frame == frame_number)
+			if ((hsotg->core_params->uframe_sched > 0 &&
+			     dwc2_frame_num_le(qh->sched_frame, frame_number))
+			 || (hsotg->core_params->uframe_sched <= 0 &&
+			     qh->sched_frame == frame_number))
 				list_move(&qh->qh_list_entry,
 					  &hsotg->periodic_sched_ready);
 			else