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>

4 files changed, 9 insertions, 5 deletions

diff --git a/drivers/media/video/ivtv/ivtv-driver.h b/drivers/media/video/ivtv/ivtv-driver.h
index be2d779dba12..bc29436e8a3c 100644
--- a/drivers/media/video/ivtv/ivtv-driver.h
+++ b/drivers/media/video/ivtv/ivtv-driver.h
@@ -506,6 +506,8 @@ struct yuv_playback_info
         struct v4l2_rect main_rect;
         u32 v4l2_src_w;
         u32 v4l2_src_h;
+
+        u8 running; /* Have any frames been displayed */
 };
 
 #define IVTV_VBI_FRAMES 32
diff --git a/drivers/media/video/ivtv/ivtv-ioctl.c b/drivers/media/video/ivtv/ivtv-ioctl.c
index 3c2628a63015..8696527ab134 100644
--- a/drivers/media/video/ivtv/ivtv-ioctl.c
+++ b/drivers/media/video/ivtv/ivtv-ioctl.c
@@ -644,8 +644,6 @@ static int ivtv_s_fmt_vid_out(struct file *file, void *fh, struct v4l2_format *f
                 itv->dma_data_req_size =
                         1080 * ((yi->v4l2_src_h + 31) & ~31);
 
-        /* Force update of yuv registers */
-        yi->yuv_forced_update = 1;
         return 0;
 }
 
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];
                         }
 
diff --git a/drivers/media/video/ivtv/ivtv-yuv.c b/drivers/media/video/ivtv/ivtv-yuv.c
index 3092ff1d00a0..ee91107376c7 100644
--- a/drivers/media/video/ivtv/ivtv-yuv.c
+++ b/drivers/media/video/ivtv/ivtv-yuv.c
@@ -1147,6 +1147,7 @@ void ivtv_yuv_close(struct ivtv *itv)
         IVTV_DEBUG_YUV("ivtv_yuv_close\n");
         ivtv_waitq(&itv->vsync_waitq);
 
+        yi->running = 0;
         atomic_set(&yi->next_dma_frame, -1);
         atomic_set(&yi->next_fill_frame, 0);