Drivers Nouveau , Wayland plasma and OM Lx 43

hello

i have a strange result with choice plasma connexion
Kwin - wayland is using 120% cpu ( 20% by core cpu ) in idle
startplasma-waylandsesssion for user 1001 lanunched by kwin-wayland is using to much cpu

i have also to report these errors

nov. 13 07:53:47 omv kernel: MXM: GUID detected in BIOS
nov. 13 07:53:47 omv kernel: nouveau 0000:07:00.0: bus: MMIO write of 8000012c FAULT at 10eb14 [ PRIVRING ]
nov. 13 07:53:47 omv kernel: nouveau 0000:07:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0015 address=0x0 flags=0x0000]
nov. 13 07:53:47 omv kernel: nouveau 0000:07:00.0: DRM: failed to create kernel channel, -22

Amd-vi should work ( this is a X570 motherboard with 3600XT cpu & Nvidia 970 card ) and not interfere with nouveau

Maybe llvmpipe is used instead opensource NVIDIA driver?
Llvmpipe is implementation working on cpu, so this can explain big cpu usage.

Please run:
glxinfo | grep renderer

and paste output. If you see command not found, install first glxinfo

result

 glxinfo | grep renderer
    GLX_MESA_query_renderer, GLX_MESA_swap_control, GLX_NV_float_buffer, 
    GLX_MESA_query_renderer, GLX_OML_swap_method, GLX_SGIS_multisample, 
Extended renderer info (GLX_MESA_query_renderer):
OpenGL renderer string: llvmpipe (LLVM 13.0.0, 256 bits)

so nouveau is not working