Difference between revisions of "Hybrid graphics"

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(Undo revision 521142 by Lf (talk) - trivial hardware-specific script, one specific model is not "many machines")
 
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=== Fully Power Down Discrete GPU ===
 
=== Fully Power Down Discrete GPU ===
  
You may want to turn off the high-performance graphics processor to save battery power, this can be done by installing the {{pkg|acpi_call}} package.
+
You may want to turn off the high-performance graphics processor to save battery power.
 +
 
 +
==== Using bbswitch ====
 +
 
 +
With a NVidia GPU, this can be more safely done using [[bbswitch]],
 +
which consists of a kernel package that automatically and issues the correct
 +
ACPI calls to disable the discrete GPU when not needed, or automatically at boot.
 +
 
 +
==== Using acpi_call ====
 +
 
 +
Otherwise, and for GPUs not supported by bbswitch, the same can be done manually installing the {{pkg|acpi_call}} package.
  
 
{{Tip|For kernels not in the [[Official repositories]], the {{Pkg|acpi_call-dkms}} is an alternative. See also [[DKMS]].}}  
 
{{Tip|For kernels not in the [[Official repositories]], the {{Pkg|acpi_call-dkms}} is an alternative. See also [[DKMS]].}}  
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See the "works"? This means the script found a bus which your GPU sits on and it has now turned off the chip. To confirm this, your battery time remaining should have increased.
 
See the "works"? This means the script found a bus which your GPU sits on and it has now turned off the chip. To confirm this, your battery time remaining should have increased.
 
{{Note|To turn the GPU back on just reboot.}}
 
  
 
Currently, the chip will turn back on with the next reboot. To get around this, add the kernel module to the array of modules to load at boot:
 
Currently, the chip will turn back on with the next reboot. To get around this, add the kernel module to the array of modules to load at boot:
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acpi_call}}
 
acpi_call}}
  
To turn off the GPU at boot we could just run the above script but honestly that is not very elegant so instead lets make use of systemd's tmpfiles.  
+
To turn off the GPU at boot it is possible to use [[Systemd#Temporary files|systemd-tmpfiles]].  
  
 
{{hc|/etc/tmpfiles.d/acpi_call.conf|
 
{{hc|/etc/tmpfiles.d/acpi_call.conf|
  
w /proc/acpi/call - - - - \\_SB.PCI0.PEG0.PEGP._OFF}}
+
w /proc/acpi/call - - - - ''\\_SB.PCI0.PEG0.PEGP._OFF''}}
  
 
The above config will be loaded at boot by systemd. What it does is write the specific OFF signal to the {{ic|/proc/acpi/call}} file. Obviously, replace the {{ic|\_SB.PCI0.PEG0.PEGP._OFF}} with the one which works on your system (please note that you need to escape the backslash).
 
The above config will be loaded at boot by systemd. What it does is write the specific OFF signal to the {{ic|/proc/acpi/call}} file. Obviously, replace the {{ic|\_SB.PCI0.PEG0.PEGP._OFF}} with the one which works on your system (please note that you need to escape the backslash).
  
 
{{Tip| If you are experiencing trouble hibernating or suspending the system after disabling the GPU, try to enable it again by sending the corresponding acpi_call. See also [[Power_management#Suspend.2Fresume_service_files|Suspend/resume service files]].}}
 
{{Tip| If you are experiencing trouble hibernating or suspending the system after disabling the GPU, try to enable it again by sending the corresponding acpi_call. See also [[Power_management#Suspend.2Fresume_service_files|Suspend/resume service files]].}}

Latest revision as of 20:58, 14 May 2018

Hybrid-graphics is a concept involving two graphics cards on same computer. The laptop manufacturers developed new technologies involving two graphic cards in an single computer, with different abilities and power consumptions. Hybrid-graphics is developed to support both high performance and power saving usages.

There are a variety of technologies and each manufacturer developed its own solution to this problem. This technology is well supported on Windows but it's still quite experimental with Linux distributions. Here we try to explain a little about each approach and models and some community solutions to the lack of GNU/Linux systems support.

First Generation Hybrid Model (Basic Switching)

Note: Unless your notebook is from the last decade, it’s most likely using dynamic switching.

The first generation of notebooks with hybrid graphics follow an approach that involves a two graphic card setup with a hardware multiplexer (MUX). It allows power save and low-end 3D rendering by using an Integrated Graphics Processor (IGP); or a major power consumption with 3D rendering performance using a Dedicated/Discrete Graphics Processor (DGP). This model makes the user choose (at boot time or at login time) within the two power/graphics profiles and is almost fixed through all the user session. The switch is done by a similar workflow:

  • Turn off the display
  • Turn on the DGP
  • Switch the multiplexer
  • Turn off the IGP
  • Turn the display on again

This switch is somewhat rough and adds some blinks and black screens in laptops that could do it "on the fly". Later approaches made the transition a little more user-friendly.

Dynamic Switching Model

Note: This model is utilized by most manufacturers as of 2016.

Most of the new Hybrid-graphics technologies involve two graphic cards as the basic switching but now the DGP and IGP are plugged to a framebuffer and there is no hardware multiplexer. The IGP is always on and the DGP is switched on/off when there is a need in power-save or performance-rendering. In most cases there is no way to use only the DGP and all the switching and rendering is controlled by software. At startup, the Linux kernel starts using a video mode and setting up low-level graphic drivers which will be used by the applications. Most of the Linux distributions then use X.org to create a graphical environment. Finally, a few other softwares are launched, first a login manager and then a window manager, and so on. This hierarchical system has been designed to be used in most of cases on a single graphic card.

Note:
Read NVIDIA Optimus and Bumblebee for details about NVidia using hybrid graphics with NVidia’s proprietary driver.
Read PRIME basically everything else (like AMD Radeon and NVidia GPUs with Nouveau driver).

Fully Power Down Discrete GPU

You may want to turn off the high-performance graphics processor to save battery power.

Using bbswitch

With a NVidia GPU, this can be more safely done using bbswitch, which consists of a kernel package that automatically and issues the correct ACPI calls to disable the discrete GPU when not needed, or automatically at boot.

Using acpi_call

Otherwise, and for GPUs not supported by bbswitch, the same can be done manually installing the acpi_call package.

Tip: For kernels not in the Official repositories, the acpi_call-dkms is an alternative. See also DKMS.

Once installed load the kernel module:

# modprobe acpi_call

With the kernel module loaded run the following:

# /usr/share/acpi_call/examples/turn_off_gpu.sh

This script will go through all the known data buses and attempt to turn them off. You will get an output similar to the following:

Trying \_SB.PCI0.P0P1.VGA._OFF: failed
Trying \_SB.PCI0.P0P2.VGA._OFF: failed
Trying \_SB_.PCI0.OVGA.ATPX: failed
Trying \_SB_.PCI0.OVGA.XTPX: failed
Trying \_SB.PCI0.P0P3.PEGP._OFF: failed
Trying \_SB.PCI0.P0P2.PEGP._OFF: failed
Trying \_SB.PCI0.P0P1.PEGP._OFF: failed
Trying \_SB.PCI0.MXR0.MXM0._OFF: failed
Trying \_SB.PCI0.PEG1.GFX0._OFF: failed
Trying \_SB.PCI0.PEG0.GFX0.DOFF: failed
Trying \_SB.PCI0.PEG1.GFX0.DOFF: failed
Trying \_SB.PCI0.PEG0.PEGP._OFF: works!
Trying \_SB.PCI0.XVR0.Z01I.DGOF: failed
Trying \_SB.PCI0.PEGR.GFX0._OFF: failed
Trying \_SB.PCI0.PEG.VID._OFF: failed
Trying \_SB.PCI0.PEG0.VID._OFF: failed
Trying \_SB.PCI0.P0P2.DGPU._OFF: failed
Trying \_SB.PCI0.P0P4.DGPU.DOFF: failed
Trying \_SB.PCI0.IXVE.IGPU.DGOF: failed
Trying \_SB.PCI0.RP00.VGA._PS3: failed
Trying \_SB.PCI0.RP00.VGA.P3MO: failed
Trying \_SB.PCI0.GFX0.DSM._T_0: failed
Trying \_SB.PCI0.LPC.EC.PUBS._OFF: failed
Trying \_SB.PCI0.P0P2.NVID._OFF: failed
Trying \_SB.PCI0.P0P2.VGA.PX02: failed
Trying \_SB_.PCI0.PEGP.DGFX._OFF: failed
Trying \_SB_.PCI0.VGA.PX02: failed

See the "works"? This means the script found a bus which your GPU sits on and it has now turned off the chip. To confirm this, your battery time remaining should have increased.

Currently, the chip will turn back on with the next reboot. To get around this, add the kernel module to the array of modules to load at boot:

/etc/modules-load.d/acpi_call.conf
#Load 'acpi_call.ko' at boot.

acpi_call

To turn off the GPU at boot it is possible to use systemd-tmpfiles.

/etc/tmpfiles.d/acpi_call.conf

w /proc/acpi/call - - - - \\_SB.PCI0.PEG0.PEGP._OFF

The above config will be loaded at boot by systemd. What it does is write the specific OFF signal to the /proc/acpi/call file. Obviously, replace the \_SB.PCI0.PEG0.PEGP._OFF with the one which works on your system (please note that you need to escape the backslash).

Tip: If you are experiencing trouble hibernating or suspending the system after disabling the GPU, try to enable it again by sending the corresponding acpi_call. See also Suspend/resume service files.