Use low_latency_mode=1 v4l2 is block

Robotics & Edge Computing Jetson & Embedded Systems Jetson TX2
1

we use the TX2-NX board on Version 32.7.2
we use the camera ISX019，10fps， Due to hardware reasons, when we use the trigger signal, there will be a loss of 5 frames

while we use the normal v4l-ctl common like this

v4l2-ctl --set-ctrl --set-ctrl bypass_mode=0 --stream-mmap  -d /dev/video0

it can see like that

<<<<<<<<<< 10fps
<<<<<<<< 9fps
<<<<<<< 8fps
<<<<<<<<<< 9fps

This is reasonable and what we expected

while we use the low_latency_mode v4l-ctl common like this

v4l2-ctl --set-ctrl low_latency_mode=1 --set-ctrl bypass_mode=0 --stream-mmap  -d /dev/video0

it can see like that

<<<<<<<<<< 10fps
<<<<<

This will be blocked here

and dmesg show that always

tgra-vi4 15700000.vi: PXL_SOF syncpt timeout! err = -11
tgra-vi4 15700000.vi: PXL_SOF syncpt timeout! err = -11
tgra-vi4 15700000.vi: PXL_SOF syncpt timeout! err = -11
tgra-vi4 15700000.vi: ATMOP_FE syncpy timeout! err = -11
tgra-vi4 15700000.vi: PXL_SOF syncpt timeout! err = -11
......

But we can observe the mipi signal using an oscilloscope

3

Increase the timeout to try.

./vi/vi4_fops.c:        chan->timeout = msecs_to_jiffies(200);
1 Like
4

Thank you , the problem have be sloved

5

I would like to know if this modification will have any other negative effects

6

I don’t come out any negative effects, but we didn’t have complete test for the low latency mode.

7

By the way, is there no issue of two frames delay after version 35.0 on other platfrom like orin nx?

8

As my previous comment we don’t have a test case for the low latency mode for each release.

Thanks

9

Sorry, I may have misunderstood, only TEGRA_ 19x architecture does not require the use of low_latency_mode

10

Suppose yes, due to the VI5 driver implement is different with VI2/VI4.

11

thank you

13

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