[blfs-support] Unable to find vgaswitcheroo to disable discrete gpu

Sebastien Fievet sebastien.fievet at free.fr
Sat Sep 7 11:44:40 PDT 2013


On Sat, 7 Sep 2013 12:18:12 +0200 (CEST)
joao.moreira at free.fr wrote:

> Hi all,
> 
> I've built an LFS system on an HP Pavilion laptop, which overheats enormously
> due to the high-performance discrete gpu. I'd like to disable it and use only
> the low-power integrated gpu. I managed to this under Fedora, by writing
> to /sys/kernel/debug/vgaswitcheroo/switch, but I don't have this file under
> LFS.
> 
> I had already determined that my 3.2.6 kernel did not have vgaswitcheroo
> enabled, so I recompiled it with CONFIG_VGA_SWITCHEROO=y. I also did not have
> debugfs mounted, so I added that in /etc/fstab. So now when I boot I see :
> 
> root [ /sys/kernel/debug ]# pwd
> /sys/kernel/debug
> root [ /sys/kernel/debug ]# ls -l
> total 0
> drwxr-xr-x  2 root root 0 Sep  7  2013 acpi
> drwxr-xr-x 30 root root 0 Sep  7  2013 bdi
> drwxr-xr-x  3 root root 0 Sep  7  2013 boot_params
> drwxr-xr-x  4 root root 0 Sep  7  2013 dri
> drwxr-xr-x  3 root root 0 Sep  7  2013 hid
> drwxr-xr-x  3 root root 0 Sep  7  2013 ieee80211
> drwxr-xr-x  2 root root 0 Sep  7  2013 kprobes
> drwxr-xr-x  2 root root 0 Sep  7  2013 mce
> -r--r--r--  1 root root 0 Sep  7  2013 suspend_stats
> drwxr-xr-x  5 root root 0 Sep  7  2013 tracing
> drwxr-xr-x  6 root root 0 Sep  7  2013 usb
> -r--r--r--  1 root root 0 Sep  7  2013 wakeup_sources
> drwxr-xr-x  2 root root 0 Sep  7  2013 x86
> root [ /sys/kernel/debug ]#
> 
> There is no vgaswitcheroo directory. Any idea what's missing ? What do I need
> to do more to make it appear ?
> 
> Thanks in advance for your help,
> 
> Joao
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You also need to have KMS enabled drivers (for both iGPU and dGPU).

Seb.



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