/etc/default/grub

GRUB_CMDLINE_LINUX_DEFAULT="radeon.runpm=0"

sudo update-grub

Voir https://bbs.archlinux.org/viewtopic.php?id=177254

/etc/modprobe.d/boot_radeon.conf

options radeon dpm=1
options radeon audio=1
options radeon runpm=0

sudo update-initramfs -k all -u

cat /sys/kernel/debug/vgaswitcheroo/switch
echo OFF > /sys/kernel/debug/vgaswitcheroo/switch
echo DIS > /sys/kernel/debug/vgaswitcheroo/switch