Garten Eden

#linux #programming #android #online #stuff

Radeon News in Kernel 2.6.35

As chances are that the Kernel Team is going through the ultimate RC, I will provide you interesting pieces of information out of the graphic segment for ATI/AMD cards and also trivia from other areas.

One of the biggest changes are related to the management of the kernel development itself. So Linus Torvalds is not willing to allow large commits after the merge window anymore. Let’s see if it will come off this time...

Graphics: We have really great news in this area—especially for notebook users. After having seen basic power management support for the KMS-mode of ATI cards out of the generations R300 and later (HD2000/3000/4000) in the previous kernel 2.6.34, we can now look forward to mentionable enhancements here: Not only added the developers a profile-based power-saving-system which is able to adjust the grade of power consumption automatically/dynamically, but you can also choose a profile setting the GPU into one of the modes default, low, high and auto. While low and high activate the lowest performance (highest power consumption) or aggressive power saving (lowest performance), default keeps the chips standard clock and voltage without adjusting at all. auto on the other hand alternates between low and high performance controlled by the state of power supply. You can enable these manual modes by simply echo profile in /sys/class/drm/card0/device/power_method so you can choose between the modes listed above in the file /sys/class/drm/card0/device/power_profile.
In order to let the driver decide automatically, an echo dynpm into the first file answers this purpose. Henceforward it will change the clock by checking the graphic load (this is done by determining the waiting fences). However, graphics developer Alex Deucher cautions against errors and artifacts while using this mode.

This great news notwithstanding, certainly ATI+Linux users would appreciate the ability of adjusting the core voltage as well instead of just the clock*.

Besides: There are several optimization patches in the network stack increasing speed mainly for servers and multicore systems. Moreover, AMDs Turbo-Core for six-core processors also experiences essential improvements. Worth mentioning is the new “Memory Compaction” function allowing the kernel to defragment the RAM and thus expand the contiguous free space.

As a matter of course, one can find more enhancements and progressive work done which I am not capable of providing sufficiently here. By mentioning the constant updates on Btrfs, I invite you receive information from LKML.org, the official Linux Kernel Mailing List where you can find any discussion and cutting-edge announcements. Additionally, you can read Linus summary about the previous RCs.

Installation on Ubuntu

For quite a long time Canonical offers pre-compiled current kernels. Attention should be paid to the fact that new available kernels are not supported in all Ubuntu versions. A suffix indicates the version the kernel is related to (e.g. -lucid). The folders without any suffix are Vanilla-Kernels and should work on most releases.

In order to install a kernel, you have to download one from the Kernel Teams site and install it as usual. Having this done, it should be listed on top in Grub so you can boot it. In case you appearance problems, you just have choose the old kernel from Grubs boot list and deinstall the new one in your packaging tool like Synaptic.

Looking on the updated Feature Matrix of the radeon driver, you can see that voltage adjusting is ready as well! So lets hope well find the changes in kernel 2.6.36.

People keep asking me why sudo echo X > file does not work. Well, there are two parts in this expression and the pipe is the one needing root access. In order to achieve that you have again two possibilities: Either you start a login-root-shell with sudo su -l or—and this is the favorite way—you redirect your echo part with tee:

echo "auto" | sudo tee /sys/class/drm/card0/device/power_profile

That way you run in auto mode.

updated Jul-29/2010 01:10pm

updated Nov-09/2010 22:29pm

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