V4L: ivtv: Add locking to ensure stream setup is atomic

Starting an MPEG and VBI capture simultaneously caused errors in
the VBI setup: this setup was done twice when it should be done
only for the first stream that is opened.
Added a mutex to prevent this from happening.

(cherry picked from commit f8859691)
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>

drivers/media/video/ivtv/ivtv-driver.c

@@ -622,6 +622,7 @@ static int __devinit ivtv_init_struct1(struct ivtv *itv)
 	itv->enc_mbox.max_mbox = 2; /* the encoder has 3 mailboxes (0-2) */
 	itv->dec_mbox.max_mbox = 1; /* the decoder has 2 mailboxes (0-1) */
 
+	mutex_init(&itv->serialize_lock);
 	mutex_init(&itv->i2c_bus_lock);
 	mutex_init(&itv->udma.lock);
 

drivers/media/video/ivtv/ivtv-driver.h

@@ -722,6 +722,7 @@ struct ivtv {
 	int search_pack_header;
 
 	spinlock_t dma_reg_lock; /* lock access to DMA engine registers */
+	struct mutex serialize_lock;  /* lock used to serialize starting streams */
 
 	/* User based DMA for OSD */
 	struct ivtv_user_dma udma;

drivers/media/video/ivtv/ivtv-streams.c

@@ -446,6 +446,9 @@ int ivtv_start_v4l2_encode_stream(struct ivtv_stream *s)
 	if (s->v4l2dev == NULL)
 		return -EINVAL;
 
+	/* Big serialization lock to ensure no two streams are started
+	   simultaneously: that can give all sorts of weird results. */
+	mutex_lock(&itv->serialize_lock);
 	IVTV_DEBUG_INFO("Start encoder stream %s\n", s->name);
 
 	switch (s->type) {
@@ -487,6 +490,7 @@ int ivtv_start_v4l2_encode_stream(struct ivtv_stream *s)
 			0, sizeof(itv->vbi.sliced_mpeg_size));
 		break;
 	default:
+		mutex_unlock(&itv->serialize_lock);
 		return -EINVAL;
 	}
 	s->subtype = subtype;
@@ -568,6 +572,7 @@ int ivtv_start_v4l2_encode_stream(struct ivtv_stream *s)
 	if (ivtv_vapi(itv, CX2341X_ENC_START_CAPTURE, 2, captype, subtype))
 	{
 		IVTV_DEBUG_WARN( "Error starting capture!\n");
+		mutex_unlock(&itv->serialize_lock);
 		return -EINVAL;
 	}
 
@@ -583,6 +588,7 @@ int ivtv_start_v4l2_encode_stream(struct ivtv_stream *s)
 
 	/* you're live! sit back and await interrupts :) */
 	atomic_inc(&itv->capturing);
+	mutex_unlock(&itv->serialize_lock);
 	return 0;
 }
 
@@ -762,17 +768,6 @@ int ivtv_stop_v4l2_encode_stream(struct ivtv_stream *s, int gop_end)
 	/* when: 0 =  end of GOP  1 = NOW!, type: 0 = mpeg, subtype: 3 = video+audio */
 	ivtv_vapi(itv, CX2341X_ENC_STOP_CAPTURE, 3, stopmode, cap_type, s->subtype);
 
-	/* only run these if we're shutting down the last cap */
-	if (atomic_read(&itv->capturing) - 1 == 0) {
-		/* event notification (off) */
-		if (test_and_clear_bit(IVTV_F_I_DIG_RST, &itv->i_flags)) {
-			/* type: 0 = refresh */
-			/* on/off: 0 = off, intr: 0x10000000, mbox_id: -1: none */
-			ivtv_vapi(itv, CX2341X_ENC_SET_EVENT_NOTIFICATION, 4, 0, 0, IVTV_IRQ_ENC_VIM_RST, -1);
-			ivtv_set_irq_mask(itv, IVTV_IRQ_ENC_VIM_RST);
-		}
-	}
-
 	then = jiffies;
 
 	if (!test_bit(IVTV_F_S_PASSTHROUGH, &s->s_flags)) {
@@ -840,17 +835,30 @@ int ivtv_stop_v4l2_encode_stream(struct ivtv_stream *s, int gop_end)
 	/* Clear capture and no-read bits */
 	clear_bit(IVTV_F_S_STREAMING, &s->s_flags);
 
+	/* ensure these global cleanup actions are done only once */
+	mutex_lock(&itv->serialize_lock);
+
 	if (s->type == IVTV_ENC_STREAM_TYPE_VBI)
 		ivtv_set_irq_mask(itv, IVTV_IRQ_ENC_VBI_CAP);
 
 	if (atomic_read(&itv->capturing) > 0) {
+		mutex_unlock(&itv->serialize_lock);
 		return 0;
 	}
 
 	/* Set the following Interrupt mask bits for capture */
 	ivtv_set_irq_mask(itv, IVTV_IRQ_MASK_CAPTURE);
 
+	/* event notification (off) */
+	if (test_and_clear_bit(IVTV_F_I_DIG_RST, &itv->i_flags)) {
+		/* type: 0 = refresh */
+		/* on/off: 0 = off, intr: 0x10000000, mbox_id: -1: none */
+		ivtv_vapi(itv, CX2341X_ENC_SET_EVENT_NOTIFICATION, 4, 0, 0, IVTV_IRQ_ENC_VIM_RST, -1);
+		ivtv_set_irq_mask(itv, IVTV_IRQ_ENC_VIM_RST);
+	}
+
 	wake_up(&s->waitq);
+	mutex_unlock(&itv->serialize_lock);
 
 	return 0;
 }