Screen tearing pi4

[jcforbes]

Pi Model or other hardware: Pi4 8gb B Rev 1.5
Power Supply used: Official
RetroPie Version Used (eg 3.6, 3.8.1, 4.1 - do not write latest): 5.10.103-v71+
Built From: Raspberry Pi Imager
USB Devices connected: None
Controller used: Xbox Series X
Error messages received: None
Verbose log (if relevant):
Guide used: Every forum post I could find, but all are old
Emulator: gamegear, megadrive, NES
How to replicate the problem: Play games
Display: LG C3 4k TV via HDMI

I'm having big screen tearing issues. This is a new build as of yesterday, all updates run. I first noticed issues in Sonic the Hedgehog on gamegear. Turning on smoothing helped. I later overclocked in an attempt to get N64 going, and tearing got worse again and expanded to NES games like Mario 3 and megadrive Sonic 1. I tried going to KMS, but it caused crashes when loading a game. I found a forum thread that mentioned that is related to the newer kernals and audio; I was able to confirm that it doesn't crash with dtparam=audio=off, but games run at ludicrous speed and also of course no audio.

In attempting to diagnose I have removed the GPU overclock and set arm_freq=1500 which hasn't improved anything.

All info I could find on anything related is at least 12+ months old. Whats the latest best practice with KMS vs FKMS? Whats the latest advice on fixing tearing?

Confix.txt:

# For more options and information see
# http://rpf.io/configtxt
# Some settings may impact device functionality. See link above for details

# uncomment if you get no picture on HDMI for a default "safe" mode
#hdmi_safe=1

# uncomment this if your display has a black border of unused pixels visible
# and your display can output without overscan
disable_overscan=1

# uncomment the following to adjust overscan. Use positive numbers if console
# goes off screen, and negative if there is too much border
#overscan_left=16
#overscan_right=16
#overscan_top=16
#overscan_bottom=16

# uncomment to force a console size. By default it will be display's size minus
# overscan.
#framebuffer_width=1280
#framebuffer_height=720

# uncomment if hdmi display is not detected and composite is being output
#hdmi_force_hotplug=1

# uncomment to force a specific HDMI mode (this will force VGA)
#hdmi_group=1
#hdmi_mode=1

# uncomment to force a HDMI mode rather than DVI. This can make audio work in
# DMT (computer monitor) modes
#hdmi_drive=2

# uncomment to increase signal to HDMI, if you have interference, blanking, or
# no display
#config_hdmi_boost=4

# uncomment for composite PAL
#sdtv_mode=2

#uncomment to overclock the arm. 700 MHz is the default.
#over_voltage=6
arm_freq=1500
#gpu_freq=750

# Uncomment some or all of these to enable the optional hardware interfaces
#dtparam=i2c_arm=on
#dtparam=i2s=on
#dtparam=spi=on

# Uncomment this to enable infrared communication.
#dtoverlay=gpio-ir,gpio_pin=17
#dtoverlay=gpio-ir-tx,gpio_pin=18

# Additional overlays and parameters are documented /boot/overlays/README

# Enable audio (loads snd_bcm2835)
dtparam=audio=off

[pi4]
# Enable DRM VC4 V3D driver on top of the dispmanx display stack
dtoverlay=vc4-kms-v3d,noaudio
# dtoverlay=vc4-fkms-v3d
max_framebuffers=2

[all]
dtoverlay=vc4-kms-v3d,noaudio
#dtoverlay=vc4-fkms-v3d
#overscan_scale=1
#hdmi_enable_4kp60=1

[mitu]

@jcforbes said in Screen tearing pi4:

All info I could find on anything related is at least 12+ months old. Whats the latest best practice with KMS vs FKMS? Whats the latest advice on fixing tearing?

For the buster version of RetroPie (which comes with the RetroPie image), using fkms is recommended. Lower the resolution to 1080p (see the docs) and check again if you still have the issue.

If you wish to use the 'full' KMS driver, you'll need to manually install over the latest RaspiOS (based on Debian bookworm) since that version contains the updated kernel for KMS on the Pi4 (and later) model. Just changing from fkms to kms in the config.txt is not going to be enough.

[jcforbes]

@mitu thanks, the issue is now resolved. I believed I disabled 4k at various points but I thought that framebuffer_width and height were sufficient for that. Using hdmi_group=1 and hdmi_mode=16 resolved the issue.