bcm2835-camera: Fix timestamp calculation problem (raspberrypi#2214)

* bcm2835-camera: Fix timestamp calculation problem

Use div_s64_rem() to convert usec timestamp to timeval
to avoid integer signedness bug.

* bcm2835-camera: Store kernel start time in NSEC instead of USEC

* bcm2835-camera: Reword debug message for clarity

drivers/media/platform/bcm2835/bcm2835-camera.c

@@ -363,37 +363,17 @@ static void buffer_cb(struct vchiq_mmal_instance *instance,
  buf->vb.vb2_buf.timestamp);
 
  } else if(pts != 0) {
- struct timeval timestamp;
  s64 runtime_us = pts -
  dev->capture.vc_start_timestamp;
- u32 div = 0;
- u32 rem = 0;
-
- div =
- div_u64_rem(runtime_us, USEC_PER_SEC, &rem);
- timestamp.tv_sec =
- dev->capture.kernel_start_ts.tv_sec + div;
- timestamp.tv_usec =
- dev->capture.kernel_start_ts.tv_usec + rem;
-
- if (timestamp.tv_usec >=
- USEC_PER_SEC) {
- timestamp.tv_sec++;
- timestamp.tv_usec -=
- USEC_PER_SEC;
- }
+ buf->vb.vb2_buf.timestamp = (runtime_us * NSEC_PER_USEC) +
+ dev->capture.kernel_start_timestamp;
  v4l2_dbg(1, bcm2835_v4l2_debug, &dev->v4l2_dev,
- "Convert start time %d.%06d and %llu "
- "with offset %llu to %d.%06d\n",
- (int)dev->capture.kernel_start_ts.
- tv_sec,
- (int)dev->capture.kernel_start_ts.
- tv_usec,
- dev->capture.vc_start_timestamp, pts,
- (int)timestamp.tv_sec,
- (int)timestamp.tv_usec);
- buf->vb.vb2_buf.timestamp = timestamp.tv_sec * 1000000000ULL +
- timestamp.tv_usec * 1000ULL;
+ "Buffer time set as converted timestamp - %llu "
+ "= (pts [%lld usec] - vc start time [%llu usec]) "
+ "+ kernel start time [%llu nsec]\n",
+ buf->vb.vb2_buf.timestamp,
+ pts, dev->capture.vc_start_timestamp,
+ dev->capture.kernel_start_timestamp);
  } else {
  if (dev->capture.last_timestamp) {
  buf->vb.vb2_buf.timestamp = dev->capture.last_timestamp;
@@ -403,8 +383,7 @@ static void buffer_cb(struct vchiq_mmal_instance *instance,
  }
  else {
  buf->vb.vb2_buf.timestamp =
- dev->capture.kernel_start_ts.tv_sec * 1000000000ULL +
- dev->capture.kernel_start_ts.tv_usec * 1000ULL;
+ dev->capture.kernel_start_timestamp;
  v4l2_dbg(1, bcm2835_v4l2_debug, &dev->v4l2_dev,
  "Buffer time set as start timestamp - %lld",
  buf->vb.vb2_buf.timestamp);
@@ -586,7 +565,7 @@ static int start_streaming(struct vb2_queue *vq, unsigned int count)
 
  dev->capture.last_timestamp = 0;
 
- v4l2_get_timestamp(&dev->capture.kernel_start_ts);
+ dev->capture.kernel_start_timestamp = ktime_get_ns();
 
  /* enable the camera port */
  dev->capture.port->cb_ctx = dev;

drivers/media/platform/bcm2835/bcm2835-camera.h

@@ -92,7 +92,7 @@ struct bm2835_mmal_dev {
  /* VC start timestamp for streaming */
  s64 vc_start_timestamp;
  /* Kernel start timestamp for streaming */
- struct timeval kernel_start_ts;
+ u64 kernel_start_timestamp;
  /* Timestamp of last frame */
  u64 last_timestamp;