V4L/DVB (9596): cx18: Further changes to improve mailbox protocol integrity & performnce

All waits for cx18 mailbox API commands are now uninterruptable.  Added
code to collect mailbox ack statistics.  Tweaked timeouts based on collected
stats and video vertical frame and field rates.

Signed-off-by: Andy Walls <awalls@radix.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 30 insertions, 17 deletions

diff --git a/drivers/media/video/cx18/cx18-mailbox.c b/drivers/media/video/cx18/cx18-mailbox.c
index 0de4b9a7bbc..35f7188d4d3 100644
--- a/drivers/media/video/cx18/cx18-mailbox.c
+++ b/drivers/media/video/cx18/cx18-mailbox.c
@@ -118,6 +118,12 @@ long cx18_mb_ack(struct cx18 *cx, const struct cx18_mailbox *mb, int rpu)
 	return 0;
 }
 
+static void cx18_api_log_ack_delay(struct cx18 *cx, int msecs)
+{
+	if (msecs > CX18_MAX_MB_ACK_DELAY)
+		msecs = CX18_MAX_MB_ACK_DELAY;
+	atomic_inc(&cx->mbox_stats.mb_ack_delay[msecs]);
+}
 
 static int cx18_api_call(struct cx18 *cx, u32 cmd, int args, u32 data[])
 {
@@ -127,8 +133,7 @@ static int cx18_api_call(struct cx18 *cx, u32 cmd, int args, u32 data[])
 	u32 __iomem *xpu_state;
 	wait_queue_head_t *waitq;
 	struct mutex *mb_lock;
-	int timeout = 100;
-	long unsigned int j, ret;
+	long int timeout, ret;
 	int i;
 
 	if (info == NULL) {
@@ -176,18 +181,18 @@ static int cx18_api_call(struct cx18 *cx, u32 cmd, int args, u32 data[])
 	 */
 	state = cx18_readl(cx, xpu_state);
 	req = cx18_readl(cx, &mb->request);
-	j = msecs_to_jiffies(timeout);
+	timeout = msecs_to_jiffies(20); /* 1 field at 50 Hz vertical refresh */
 	ret = wait_event_timeout(*waitq,
 				 (ack = cx18_readl(cx, &mb->ack)) == req,
-				 j);
+				 timeout);
 	if (req != ack) {
 		/* waited long enough, make the mbox "not busy" from our end */
 		cx18_writel(cx, req, &mb->ack);
 		CX18_ERR("mbox was found stuck busy when setting up for %s; "
 			 "clearing busy and trying to proceed\n", info->name);
-	} else if (ret != j)
+	} else if (ret != timeout)
 		CX18_DEBUG_API("waited %u usecs for busy mbox to be acked\n",
-			       jiffies_to_usecs(j-ret));
+			       jiffies_to_usecs(timeout-ret));
 
 	/* Build the outgoing mailbox */
 	req = ((req & 0xfffffffe) == 0xfffffffe) ? 1 : req + 1;
@@ -199,24 +204,28 @@ static int cx18_api_call(struct cx18 *cx, u32 cmd, int args, u32 data[])
 	cx18_writel(cx, req, &mb->request);
 	cx18_writel(cx, req - 1, &mb->ack); /* ensure ack & req are distinct */
 
-	/* Notify the XPU and wait for it to send an Ack back */
-	if (info->flags & API_FAST)
-		timeout /= 2;
-	j = msecs_to_jiffies(timeout);
+	/*
+	 * Notify the XPU and wait for it to send an Ack back
+	 * 21 ms = ~ 0.5 frames at a frame rate of 24 fps
+	 * 42 ms = ~ 1 frame at a frame rate of 24 fps
+	 */
+	timeout = msecs_to_jiffies((info->flags & API_FAST) ? 21 : 42);
 
 	CX18_DEBUG_HI_IRQ("sending interrupt SW1: %x to send %s\n",
 			  irq, info->name);
 	cx18_write_reg_expect(cx, irq, SW1_INT_SET, irq, irq);
 
-	ret = wait_event_interruptible_timeout(
+	ret = wait_event_timeout(
 		       *waitq,
 		       cx18_readl(cx, &mb->ack) == cx18_readl(cx, &mb->request),
-		       j);
+		       timeout);
 	if (ret == 0) {
 		/* Timed out */
 		mutex_unlock(mb_lock);
-		CX18_ERR("sending %s timed out waiting for RPU "
-			 "acknowledgement\n", info->name);
+		i = jiffies_to_msecs(timeout);
+		cx18_api_log_ack_delay(cx, i);
+		CX18_WARN("sending %s timed out waiting %d msecs for RPU "
+			  "acknowledgement\n", info->name, i);
 		return -EINVAL;
 	} else if (ret < 0) {
 		/* Interrupted */
@@ -224,9 +233,13 @@ static int cx18_api_call(struct cx18 *cx, u32 cmd, int args, u32 data[])
 		CX18_WARN("sending %s was interrupted waiting for RPU"
 			  "acknowledgement\n", info->name);
 		return -EINTR;
-	} else if (ret != j)
-		CX18_DEBUG_HI_API("waited %u usecs for %s to be acked\n",
-				  jiffies_to_usecs(j-ret), info->name);
+	}
+
+	i = jiffies_to_msecs(timeout-ret);
+	cx18_api_log_ack_delay(cx, i);
+	if (ret != timeout)
+		CX18_DEBUG_HI_API("waited %u msecs for %s to be acked\n",
+				  i, info->name);
 
 	/* Collect data returned by the XPU */
 	for (i = 0; i < MAX_MB_ARGUMENTS; i++)