cx18: Avoid making firmware API calls with the queue lock held

From: Andy Walls <awalls@radix.net>

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.

Priority: normal

Signed-off-by: Andy Walls <awalls@radix.net>

1 files changed, 9 insertions, 6 deletions

diff --git a/linux/drivers/media/video/cx18/cx18-mailbox.c b/linux/drivers/media/video/cx18/cx18-mailbox.c
index 2f7060cc1..eb5c31af6 100644
--- a/linux/drivers/media/video/cx18/cx18-mailbox.c
+++ b/linux/drivers/media/video/cx18/cx18-mailbox.c
@@ -163,7 +163,7 @@ static void epu_dma_done(struct cx18 *cx, struct cx18_epu_work_order *order)
 		 * it's filled in).
 		 *
 		 * cx18_queue_get buf() will detect the lost buffers
-		 * and put them back in rotation eventually.
+		 * and send them back to q_free for fw rotation eventually.
 		 */
 		if ((order->flags & CX18_F_EWO_MB_STALE_UPON_RECEIPT) &&
 		    !(id >= s->mdl_offset &&
@@ -174,24 +174,27 @@ static void epu_dma_done(struct cx18 *cx, struct cx18_epu_work_order *order)
 			break;
 		}
 		buf = cx18_queue_get_buf(s, id, mdl_ack->data_used);
+
 		CX18_DEBUG_HI_DMA("DMA DONE for %s (buffer %d)\n", s->name, id);
 		if (buf == NULL) {
 			CX18_WARN("Could not find buf %d for stream %s\n",
 				  id, s->name);
+			/* Put as many buffers as possible back into fw use */
+			cx18_stream_load_fw_queue(s);
 			continue;
 		}
 
-		cx18_buf_sync_for_cpu(s, buf);
 		if (s->type == CX18_ENC_STREAM_TYPE_TS && s->dvb.enabled) {
 			CX18_DEBUG_HI_DMA("TS recv bytesused = %d\n",
 					  buf->bytesused);
-
 			dvb_dmx_swfilter(&s->dvb.demux, buf->buf,
 					 buf->bytesused);
-
+		}
+		/* Put as many buffers as possible back into fw use */
+		cx18_stream_load_fw_queue(s);
+		/* Put back TS buffer, since it was removed from all queues */
+		if (s->type == CX18_ENC_STREAM_TYPE_TS)
 			cx18_stream_put_buf_fw(s, buf);
-		} else
-			set_bit(CX18_F_B_NEED_BUF_SWAP, &buf->b_flags);
 	}
 	wake_up(&cx->dma_waitq);
 	if (s->id != -1)