Saturday, April 3, 2010

Disabling Radeon KMS

Kernel Mode Setting (KMS) for the ATI Radeon RV280 chip is not ready for primetime yet so i decided to disable KMS and revert to User Mode Setting (UMS) for now. KMS is the future but it is too immature on the Radeon hardware. Now, how do I disable KMS?

First I changed /etc/modprobe.d/radeon-kms.conf to
option radeon modeset=0
Then I ran update-initramfs -u to copy the change into the boot RAM filesystem, and rebooted. For some reason that doesn't disable KMS. Hmm. Figure out why or find another way? Door number two please.

Next, I added the kernel parameter nomodeset in /boot/grub/menu.lst. Run update-grub and reboot. Nope. KMS is still enabled. Hmm. Figure out why or find another way? Door number two please.

Next I replaced the nomodeset kernel parameter with radeon.modeset=0, again in /boot/grub/menu.lst. Run update-grub and reboot. Ding ding ding, we have a winner! Phew! Pant, pant!

It should be abundantly clear that KMS in the Radeon driver is a work-in-progress when disabling it takes that much effort. ^_^
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2 comments:

  1. AnonymousOctober 29, 2010 at 5:55 PM

    Thank you very much for this hint, it saved my day :-)
    radeon.modeset=0 brought my x-server back to life.

    ReplyDelete
  2. darkestkhanFebruary 3, 2011 at 1:51 PM

    in case of GRUB2 I was adding nomodesetting in kernel parameter list and it worked

    ReplyDelete

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