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iMX7D : CSI MIPI configuration

Question asked by dh29 on Jul 6, 2018
Latest reply on Jul 11, 2018 by dh29

Linux Kernel: v4.9.11

 

I am now successfully capturing PROGRESSIVE video using a PAL camera via an ADV7820M. The image is clear and stable. According to the ADV7820M the PAL output should be at 50 fps...BUT...I am measuring 40 fps ??? [I am using gstreamer-1.0 with its fpsdisplaysink plug-in to capture the video and measure the received video's fps.] 

 

This difference of 40 fps instead of 50 fps lends me to think that something may not be setup correctly within CSI-MIPI of the iMX7?? The documentation for the iMX7 CSI-MIPI seems very sparse. This leads to a number of questions:

 

  • MIPI-CSI device tree has an entry for clock-frequency but where does this value come from and what's its purpose?
  • MIPI-CSI device tree has an entry for csis-wclk. The documentation states this enables use of the WRAP_CLK but what exactly is it and should I be enabling it?
  • iMX6 application notes talk of configuring the MIPI-CSI PHY clock rate to be within range of the sensor's differential clock (216 MHz in my case), but I can see nothing that states this for the iMX7, or any code that attempts to do this. Should the MIPI-CSI PHY clock be related to the sensor clock?

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