V4L/DVB (9166): ivtv - Fix potential race condition in yuv handler

Modified yuv register update handling to remove a potential race condition
which could occur with the first video frame.

Also removed a forced yuv position update, since changing the source video
dimensions or interlace settings doesn't affect the frame already being
displayed.

Signed-off-by: Ian Armstrong <ian@iarmst.demon.co.uk>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/drivers/media/video/ivtv/ivtv-irq.c b/drivers/media/video/ivtv/ivtv-irq.c
index 34f3ab827858..f5d00ec5da73 100644
--- a/drivers/media/video/ivtv/ivtv-irq.c
+++ b/drivers/media/video/ivtv/ivtv-irq.c
@@ -753,7 +753,7 @@ static void ivtv_irq_vsync(struct ivtv *itv)
          */
         unsigned int frame = read_reg(0x28c0) & 1;
         struct yuv_playback_info *yi = &itv->yuv_info;
-        int last_dma_frame = atomic_read(&itv->yuv_info.next_dma_frame);
+        int last_dma_frame = atomic_read(&yi->next_dma_frame);
         struct yuv_frame_info *f = &yi->new_frame_info[last_dma_frame];
 
         if (0) IVTV_DEBUG_IRQ("DEC VSYNC\n");
@@ -772,6 +772,7 @@ static void ivtv_irq_vsync(struct ivtv *itv)
                                 next_dma_frame = (next_dma_frame + 1) % IVTV_YUV_BUFFERS;
                                 atomic_set(&yi->next_dma_frame, next_dma_frame);
                                 yi->fields_lapsed = -1;
+                                yi->running = 1;
                         }
                 }
         }
@@ -804,9 +805,11 @@ static void ivtv_irq_vsync(struct ivtv *itv)
                 }
 
                 /* Check if we need to update the yuv registers */
-                if ((yi->yuv_forced_update || f->update) && last_dma_frame != -1) {
+                if (yi->running && (yi->yuv_forced_update || f->update)) {
                         if (!f->update) {
-                                last_dma_frame = (u8)(last_dma_frame - 1) % IVTV_YUV_BUFFERS;
+                                last_dma_frame =
+                                        (u8)(atomic_read(&yi->next_dma_frame) -
+                                                 1) % IVTV_YUV_BUFFERS;
                                 f = &yi->new_frame_info[last_dma_frame];
                         }