About the frame rate reduction problem of capture processing using CSI of Jetson TX2

We are having trouble with the following issues:
In our project, we are receiving data at 60fps from a device connected via the Jetson TX2’s CSI interface.
30fps for the expected frame rate
Will be.
There seem to be other similar cases, but no useful information is available from them.
We confirmed with TX1 and there is no problem.
It seems that it is caused by the difference in kernel version.
Now, what we know, there is an unknown latency when calling the dequeue ioctrl.
Does anyone know a solution?

Did you probe the sensor signal make sure to output is 60fps?

Thank you for your reply
It was measured. The frequency of the signal seems to be correct.
Also, when the same device was operated on TX1, the frame rate was 60 fps.
The connected device (FPGA) does not handshake. It sends data unilaterally and does not use I2C.
We think there is a problem with V4L2 of kernel Ver4.9.
Do you have any hints?

Have boost the nvcsi/vi clocks to try.

https://elinux.org/Jetson_TX2_Camera_BringUp

Thank you for your quick reply.
I will refer to the URL you gave me.
please tell me. What can you expect from trying Clock Boost?

Hello, ShaneCCC

I asked our members.
I’ve tried raising the clock to Max, but it didn’t improve.
We check the kernel log trace.
When receiving one frame of data, V4L2 considers to receive the following five events within 16 msec. But that doesn’t seem to be the case.
Are there any other points to note?

ATOMP_FS
CHANSEL_PXL_SOF
CHANSEL_LOAD_FRAMED
CHANSEL_PXL_EOF
ATOMP_FE

Could you try to increase the V blanking to try.

Thank you for your support.
I don’t understand Vertical blanking.
Does this mean Tegra settings?
Or is it compatible with the device (FPGA)?

It’s the sensor(FPGA) settings

Thank you for your support.
It means changing the Vertical blanking setting of the sensor (FPGA).
I’ll give it a try.

Hello, ShaneCCC

Following your advice, I changed the VBLANK of the sensor (FPGA).
However, it could not be improved.

The details of the changes are as follows.
1920x1200x60Hz
472.8113879us (VBLANK) 59.93950589Hz (Frame Rate)

1920x1200x55Hz
1958.790036us (VBLANK) 55.03739017Hz (Frame Rate)

Is there anything that can be considered from this result?
Also, are there any other measures you can try?

Please give me some advice.