Ubuntu – I can not find /sys/kernel/debug/vgaswitcheroo/switch

kernelvgaswitcheroo

I have enable switcheroo in kernel config .
Why is there not /sys/kernel/debug/vgaswitcheroo/switch ?

Linux ubuntu-raid-w500 2.6.38-10-generic #46-Ubuntu SMP Tue Jun 28 15:07:17 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux

My computer is Thinkpad W500 . One graphic card is ATI Mobility FireGL V5700 (512 MB). The other one is Intel Graphics Media Accelerator 4500MHD .

I am using official kernel 2.6.38-10, I do NOT customize it. I add kernel option pcie_aspm=force in GRUB_CMDLINE_LINUX_DEFAULT of /etc/default/grub

Setting modeset=1 doesn't seem to help
Here is the output of kern.log
Here is my entire bootup.

Best Answer

In Ubuntu 10.10 and up, vgaswitchheroo is already enabled so you don't need extra settings. And /sys/kernel/debug is already mounted, however you need root permissions to read the contents of /sys/kernel/debug, so using sudo su should work.

If there's still no switch, run lspci | grep VGA and make sure both cards are outputted. If one is missing a BIOS setting might be the cause, so check that.

Console example:

sergio@Sergio-L:~$ ls /sys/kernel/debug/vgaswitcheroo
ls: impossível aceder a /sys/kernel/debug/vgaswitcheroo: Permissão negada
sergio@Sergio-L:~$ sudo su
[sudo] password for sergio: 
root@Sergio-L:/home/sergio#
root@Sergio-L:/home/sergio# ls /sys/kernel/debug/vgaswitcheroo/
switch
root@Sergio-L:/home/sergio#

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Ubuntu – /sys/kernel/debug/vgaswitcheroo missing

I had the same problem: the folder vgaswitcheroo was missing. I found a solution: deactivate all proprietary drivers of your graphic card and then reboot. After that, the folder reappeared onto "/sys/kernel/debug". I hope it will help you !

Ubuntu – No vga/vgaswitcheroo in /sys/kernel/debug (Ubuntu 13.10)

I found this

There are two versions of hybrd graphics: MUXed and MUX-less. MUXed have a 
display MUX to switch the displays between the discrete and integrated cards. 
MUXed systems can be switched using vgaswitcheroo. MUX-less do not have a 
display MUX and the displays are only connected to the integrated card. On 
MUX-less systems, the discrete card is solely for rendering, not display. X 
Server 1.14 is required to support rendering and display from different cards. 
Most new laptops (2011+) are MUX-less.

So I think it's highly likely that my system (being a very recent laptop) is MUX-less (i.e. only the Intel card is actually connected to the display), and although I can "switch" through the AMD Catalyst Control Centre (should I be brave/foolish enough to install fglrx) this really just amounts to: "High performance" -> outsource hard graphics calculations to dGPU then reroute them back through the iGPU for display, "Low performance/good battery" -> do calcs on iGPU, then send directly to display. I also have no ability to switch GPUs in the BIOS, which also suggests MUX-less.

Thus, I probably will never be able to use VGA switcheroo.

One other consideration is that the radeon driver does not officially support my card yet (the 8670M code name Mars XT solar system series, not to be confused with OLAND). Thus when I boot up with open source drivers I get messages like No screens found for the radeon. Given that switcheroo needs radeon and intel both to there, it could be somehow failing because the radeon driver doesn't support my card.

If this is true, it leads to the question of how does one switch between ATI/Intel cards (without fglrx) in a MUX-less system.

Best Answer

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