Does AGX Xavier's vi5 driver have a low latency mode?

Autonomous Machines Jetson & Embedded Systems Jetson AGX Xavier
#1

In the R32.4.3 BSP kernel sources , I see that vi4 has a low-latency mode, which should improve the real-time performance of the system. Does vi5 have a corresponding mode? It is measured that there is a delay of about 100ms when using vi5 to transport images.
here is the low-latency mode code in vi4_fops.c:

    chan->sequence = 0;
     chan->timeout = msecs_to_jiffies(200);
    if (!chan->low_latency)///////*CONFIG LOW LATENCY*
	  tegra_channel_init_ring_buffer(chan);

INIT_WORK(&chan->error_work, tegra_channel_error_worker);
INIT_WORK(&chan->status_work, tegra_channel_status_worker);

if (chan->low_latency) {///////*CONFIG LOW LATENCY*
	/* Start thread to release buffers */
	chan->kthread_release = kthread_run(
				tegra_channel_kthread_release,
				chan, chan->video->name);
	if (IS_ERR(chan->kthread_release)) {
		dev_err(&chan->video->dev,
			"failed to run kthread for release\n");
		ret = PTR_ERR(chan->kthread_release);
		goto error_capture_setup;
	}
}

and here:

  static int tegra_channel_capture_frame(struct tegra_channel *chan,
			struct tegra_channel_buffer *buf)
  {
     int ret = 0;

     if (chan->low_latency)///////*CONFIG LOW LATENCY*
	ret = tegra_channel_capture_frame_multi_thread(chan, buf);
      else
	ret = tegra_channel_capture_frame_single_thread(chan, buf);

      return ret;
 }
#4

Looks like vi5 didn’t implement it. Need to confirm it internally.

#5

hello BugaoxingIguana,

as you can see,
low latency mode is using two threads approach to gather frames. one thread for the frame-start, the other for the frame-end.
Xavier’s VI-5 driver already implemented as the two threads approach. the idea is similar to VI-4,
it’s using kthread_capture_enqueue(), and kthread_capture_dequeue() for gathering capture frames and populate to user-space.
thanks

#7