Set screen resolution KMS

lostless

I just upgraded to a 4k tv and using a pi 4. I set the pi to use kms instead of fkms. I can’t find a way to set to 1080p. Raspian config gives me no options other than have monitor set resolution and i manually configured the config.txt in the boot directory to 1080p. It still wants to use 4k at 30fps and and can tell the lag. Any help?

mitu

You'll need to modify the /boot/cmdline.txt and specify the resolution there. When using the kms overlay, the resolution options in config.txt are no longer in effect.
See here for the kernel parameter syntax or here on how to apply it on a Raspberry Pi.

lostless

I made a mistake. While i am using KMS, I guess somehow in my config.txt file, the changes I made to force 1080P got commented. Maybe the raspiconfig did it when I selected to have my monitor set resolution. Anyway, I uncommented the forced resolution and now the pi is working in in 1080P. Not sure if that's how its supposed to work?