Cannot capture MIPI-CSI camera of low framerate(low_latency_mode=0)

[t.kato1]

Hello NVIDIA,

We have a Jetson Nano developer kit(B01) and develop our own driver of CSI-MIPI camera.

We have developed a RGB888 driver and have successfully captured images from the CSI-MIPI camera at a normal framerate but it was not possible to capture image at a low framerate.

  normal framerate = 13.5fps
  low framerate = 3fps or less

However, it is improved by setting of low_latency_mode.

  v4l2-ctl -d /dev/video0 --set-ctrl low_latency_mode=0 : low framerate is NG
  v4l2-ctl -d /dev/video0 --set-ctrl low_latency_mode=1 : low framerate is OK

Can you tell what changed by changing the low latency mode setting?

[ShaneCCC]

Please increase the timeout in vi2_fops.c to try.

static void tegra_channel_ec_init(struct tegra_channel *chan)
{
        /*
         * error recover initialization sequence
         * set timeout as 200 ms, use default if fps not available
         * Time limit allow CSI to capture good frames and drop error frames
         * TODO: Get frame rate from sub-device and adopt timeout
         */
        chan->timeout = msecs_to_jiffies(200);

        /*
         * Sync point FIFO full blocks host interface
         * Below setting enables SW to process error recovery
         */
        tegra_channel_write(chan, TEGRA_VI_CFG_VI_INCR_SYNCPT_CNTRL, 0x100);
}