I have a Mobility Radeon X1400 (RV500 Family) on my dell inspiron 6400 (or it's called inspiron 1501 or 1505 elsewhere). I use Open-source drivers and they work for me and I have no problem with anything except the powermanagement at kernel level. When I want to activate powersaving feature I use these commands: 1. when I use this command: echo dynpm > /sys/class/drm/card0/device/power_method nothing happens. I mean GPU frequency remain high. I even do not use a GUI. I'm in the shell. 2. when I use these commands echo profile > /sys/class/drm/card0/device/power_method echo low > /sys/class/drm/card0/device/power_profile I receive these error: kernel:[ 192.253008] NMI: PCI system error (SERR) for reason b1 on CPU 0. kernel:[ 192.253016] Dazed and confused, but trying to continue I have noticed that the kernel do not changes the GPU and Vram frequencies correctly in the profile mode. This is what I get when I set it to mid: # echo mid > /sys/class/drm/card0/device/power_profile # cat /sys/kernel/debug/dri/0/radeon_pm_info default engine clock: 432000 kHz current engine clock: 209250 kHz default memory clock: 396000 kHz current memory clock: 135000 kHz PCIE lanes: 1 This is what I get when I set it to low: # echo low > /sys/class/drm/card0/device/power_profile # cat /sys/kernel/debug/dri/0/radeon_pm_info default engine clock: 432000 kHz current engine clock: 324000 kHz default memory clock: 396000 kHz current memory clock: 135000 kHz PCIE lanes: 1 This is what I get when I set it to high: # echo high > /sys/class/drm/card0/device/power_profile # cat /sys/kernel/debug/dri/0/radeon_pm_info default engine clock: 432000 kHz current engine clock: 432000 kHz default memory clock: 396000 kHz current memory clock: 396000 kHz PCIE lanes: 0 If you look at the above values, it is obvious that the current clock of mid and low profiles should be replaced with each other. I've tested this in different distribution of GNU/Linux with different kernel versions: Including Ubuntu, LMDE, Archlinux and Chakra. with these kernel versions: 2.6.38, 2.6.39, 3.0.0 RC5, 3.0.0-1-amd64 in LMDE, and lately with 3.4.55 LTS in ubuntu 12.04.2.
I've seen the same things on my Inspiron 6400 with Radeon X1400 graphics, running 64-bit Ubuntu 16.10 with kernel 4.8.0-26-generic. Though while playing with it I saw some variations in behaviour. Sometimes in dynpm, reported frequencies were from the last profile that was used. Sometimes, changing a profile had no effect. Using vblank_mode=0 glxgears, Chrome and Firefox I am unable to see a performance difference between low and mid. There is a very definite difference between those and high profile. Performance of dynpm and high profile is identical or very close. Playing with these settings can introduce instability. After switching among profiles, going back to dynpm usually causes brief bright flashes of the screen. Those flashes never happen after setting dynpm in /etc/rc.local. Also, changing to high profile caused a total hang once, where even Magic SysRq didn't help. Yes, I also see NMIs switching to low, but those seem to have no ill effect.
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