Wow thanks for sharing that, its certainly useful information about the kernel Radeon driver I didn't know.
I wonder if its true for the AMD fusion as well or does it scale based on the CPU frequency since the are on the same die? Looks like I have some experiments to do latter.
-- Sent from my HP Pre3
On Mar 18, 2013 3:47 AM, Steven Haigh <net...@crc.id.au> wrote:
Hi all,
I've been on a path of discovery lately regarding the state of play for
ATI graphics cards. I started off using the ATI binary driver due to the
high fan speed (resulting from high power usage) of the open source driver.
I decided to take a different approach today and stick with the open
source 'radeon' driver. I managed to find that by default, the OSS
driver keeps the card in a 'high power / performance' state.
This can be changed by using the sysfs entries exposed.
I found that using the following puts the card in low power mode:
echo profile > /sys/class/drm/card0/device/power_method
echo low > /sys/class/drm/card0/device/power_profile
Now, this is great to shut the fan up, and works on multi-head systems
(more than one screen).
If you only use one screen, then you're in luck.
echo dynpm > /sys/class/drm/card0/device/power_method
The "dynpm" method dynamically changes the clocks based on the number of
pending fences, so performance is ramped up when running GPU intensive
apps, and ramped down when the GPU is idle. The reclocking is attemped
during vertical blanking periods, but due to the timing of the
reclocking functions, doesn't not always complete in the blanking
period, which can lead to flicker in the display. Due to this, dynpm
only works when a single head is active.
If you are like me and have multiple screens, you have the following
options to get power_profile to:
"default" uses the default clocks and does not change the power state.
This is the default behavior.
"auto" selects between "mid" and "high" power states based on the
whether the system is on battery power or not. The "low" power state are
selected when the monitors are in the dpms off state.
"low" forces the gpu to be in the low power state all the time. Note
that "low" can cause display problems on some laptops; this is why auto
does not use "low" when displays are active.
"mid" forces the gpu to be in the "mid" power state all the time. The
"low" power state is selected when the monitors are in the dpms off state.
"high" forces the gpu to be in the "high" power state all the time. The
"low" power state is selected when the monitors are in the dpms off state.
I've found that the 'low' setting seems to work fine in every day
desktop tasks - and it certainly causes the fan to be much, much quieter
than the default profile.
References:
* http://www.x.org/wiki/RadeonFeature
--
Steven Haigh
Email: net...@crc.id.au
Web: https://www.crc.id.au
Phone: (03) 9001 6090 - 0412 935 897
Fax: (03) 8338 0299
