V4L/DVB (9804): cx18: Avoid making firmware API calls with the queue lock held

cx18: Avoid making firmware API calls with the queue lock held.  The source
of MPEG strem corruption when not holding the queue lock was found to be that
the MPEG buffer could be retrieved by the user app before it was sync'ed for
the host cpu.  Incoming buffers are now sync'ed before being put on q_full and
releasing the queue lock.  We can thus avoid the sometimes lengthy call to
the firmware for CPU_DE_SET_MDL while holding the queue lock, so we can get
better performance.

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

1 files changed, 14 insertions, 23 deletions

diff --git a/drivers/media/video/cx18/cx18-streams.c b/drivers/media/video/cx18/cx18-streams.c
index d2690ccdf327..9ead4591b1d2 100644
--- a/drivers/media/video/cx18/cx18-streams.c
+++ b/drivers/media/video/cx18/cx18-streams.c
@@ -419,31 +419,22 @@ struct cx18_queue *cx18_stream_put_buf_fw(struct cx18_stream *s,
 	return q;
 }
 
-/* Must hold s->qlock when calling */
-void cx18_stream_load_fw_queue_nolock(struct cx18_stream *s)
+void cx18_stream_load_fw_queue(struct cx18_stream *s)
 {
+	struct cx18_queue *q;
 	struct cx18_buffer *buf;
-	struct cx18 *cx = s->cx;
 
-	/* Move from q_free to q_busy notifying the firmware: 63 buf limit */
-	while (s->handle != CX18_INVALID_TASK_HANDLE &&
-	       test_bit(CX18_F_S_STREAMING, &s->s_flags) &&
-	       atomic_read(&s->q_busy.buffers) < 63 &&
-	       !list_empty(&s->q_free.list)) {
-
-		/* Move from q_free to q_busy */
-		buf = list_entry(s->q_free.list.next, struct cx18_buffer, list);
-		list_move_tail(&buf->list, &s->q_busy.list);
-		buf->bytesused = buf->readpos = buf->b_flags = buf->skipped = 0;
-		atomic_dec(&s->q_free.buffers);
-		atomic_inc(&s->q_busy.buffers);
-
-		/* Notify firmware */
-		cx18_buf_sync_for_device(s, buf);
-		cx18_vapi(cx, CX18_CPU_DE_SET_MDL, 5, s->handle,
-		  (void __iomem *) &cx->scb->cpu_mdl[buf->id] - cx->enc_mem,
-		  1, buf->id, s->buf_size);
-	}
+	if (atomic_read(&s->q_free.buffers) == 0 ||
+	    atomic_read(&s->q_busy.buffers) >= 63)
+		return;
+
+	/* Move from q_free to q_busy notifying the firmware, until the limit */
+	do {
+		buf = cx18_dequeue(s, &s->q_free);
+		if (buf == NULL)
+			break;
+		q = cx18_stream_put_buf_fw(s, buf);
+	} while (atomic_read(&s->q_busy.buffers) < 63 && q == &s->q_busy);
 }
 
 int cx18_start_v4l2_encode_stream(struct cx18_stream *s)
@@ -543,8 +534,8 @@ int cx18_start_v4l2_encode_stream(struct cx18_stream *s)
 					&cx->scb->cpu_mdl[buf->id].paddr);
 		cx18_writel(cx, s->buf_size, &cx->scb->cpu_mdl[buf->id].length);
 	}
-	cx18_stream_load_fw_queue_nolock(s);
 	mutex_unlock(&s->qlock);
+	cx18_stream_load_fw_queue(s);
 
 	/* begin_capture */
 	if (cx18_vapi(cx, CX18_CPU_CAPTURE_START, 1, s->handle)) {