EMC Problem on armstoneA9r2 @250Mhz

    Hello,

    after upgrading to linux kernel 5.15 and running the GPU with etnaviv driver (before it was disabled), i see in EMC (german "EMV-Messung") a sharp spike at almost exactly 250Mhz, which i cannot see in the software version before (linux 4.9 with no graphic acceleration). I tried to find the PLL/clock causing this via /sys but i couldn't find any hint.


    Do you have a guess (linux kernel or gpu or something else)?


    Thank you in advance.


    Greetings,

    André Wagner

    Hello,


    with the command

    Code
    1. cat /sys/kernel/debug/clk/clk_summary


    You get an overview of all configured clocks and their actual rates. Maybe You can spot a clock that matches your measurement.


    Do you use a LVDS Display? LVDS_Clock/7=Pixelclock, so 250Mhz/7 = 35MHz which would be roughly the Pixelckock of a 7" Display.

    Gigabit Ethernet would use a 125MHz clock which would be half your measured frequency.


    Also did you try to disable different peripheries, like GPU or Ethernet an checked, if the peak is influenced?


    Did you measure the frequency in the laboratory or with a measuring probe?


    Your F&S Support Team