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Hybrid graphics

Hybrid-graphics is a concept involving two graphics cards on same computer. Laptop manufacturers have developed new technologies involving two graphic cards with different abilities and power consumptions on a single computer. Hybrid-graphics has been developed to support both high performance and power saving use cases.

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 describe some community solutions to the lack of GNU/Linux systems support.

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First Generation Hybrid Model (Basic Switching)

This section is being considered for removal.

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) between the two power/graphics profiles and is almost fixed throughout the user session. The switch is done in a workflow similar to the following:

• 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

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.

Fully Power Down Discrete GPU

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

Using bbswitch

With an NVidia GPU, this can be more safely done using bbswitch, which consists of a kernel package that automatically 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.

Once installed load the kernel module:

With the kernel module loaded, execute the script at /usr/share/acpi_call/examples/turn_off_gpu.sh

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

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.

Turning off the GPU automatically

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:

At boot

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

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).

After X server initialization

On some systems, turning off the discrete GPU before the X server is initialized may hang the system. In such cases, it may be better to disable the GPU after X server initialization, which is possible with some display managers. In LightDM, for instance, the display-setup-script seat configuration parameter could be used to execute a script as root that disables the GPU.

System76

Some System76 laptops (like the Oryx Pro) have their own unique hybrid graphics option. To make use of it, install system76-power AUR , enable the system76-power service, and run system76-power graphics hybrid .

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Intel graphics

Since Intel provides and supports open source drivers, Intel graphics are essentially plug-and-play.

For a comprehensive list of Intel GPU models and corresponding chipsets and CPUs, see Wikipedia:List of Intel graphics processing units.

Contents

Installation

Install the mesa package, which provides the DRI driver for 3D acceleration.

• For 32-bit application support, also install the lib32-mesa package from the multilib repository.
• For the DDX driver (which provides 2D acceleration in Xorg), install the xf86-video-intel package. (Often not recommended, see note below.)
• For Vulkan support (Ivy Bridge and newer), install the vulkan-intel package.

Loading

The Intel kernel module should load fine automatically on system boot.

If it does not happen, then:

• Make sure you do not have nomodeset or vga= as a kernel parameter, since Intel requires kernel mode-setting.
• Also, check that you have not disabled Intel by using any modprobe blacklisting within /etc/modprobe.d/ or /usr/lib/modprobe.d/ .

Enable early KMS

Kernel mode setting (KMS) is supported by Intel chipsets that use the i915 DRM driver and is mandatory and enabled by default.

Refer to Kernel mode setting#Early KMS start for instructions on how to enable KMS as soon as possible at the boot process.

Enable GuC / HuC firmware loading

On supported Skylake and newer processors, some video features (e.g. CBR rate control on SKL low-power encoding mode) may require the use of an updated GPU firmware,[3] which is loaded by default only on Gen 11+ hardware since Linux 5.4.[4] Enabling GuC/HuC firmware loading can cause issues on some systems; disable it if you experience freezing (for example, after resuming from hibernation).

For processors before Gen 11, it is necessary to add i915.enable_guc=2 to the kernel parameters to enable both GuC and HuC firmware loading. Alternatively, if the initramfs already includes the i915 module (see Kernel mode setting#Early KMS start), you can set these options through a file in /etc/modprobe.d/ , e.g.:

On next boot you can verify both GuC and HuC are enabled by using dmesg:

If they are not supported by your graphics adapter you will see:

Alternatively, check using:

Note that the related warning is not fatal, as explained in [5]:

Xorg configuration

There may be no need for any configuration to run Xorg.

However, if Xorg does not start, and to take advantage of some driver options, you can create an Xorg configuration file similar to the one below:

Additional options are added by the user on new lines below Driver . For the full list of options, see the intel(4) man page.

AccelMethod

You may need to indicate Option «AccelMethod» when creating a configuration file, the classical options are UXA , SNA (default) and BLT .

If you experience issues with default SNA (e.g. pixelated graphics, corrupt text, etc.), try using UXA instead, which can be done by adding the following line to your configuration file:

Module-based options

The i915 kernel module allows for configuration via module options. Some of the module options impact power saving.

A list of all options along with short descriptions and default values can be generated with the following command:

To check which options are currently enabled, run

You will note that many options default to -1, resulting in per-chip powersaving defaults. It is however possible to configure more aggressive powersaving by using module options.

Framebuffer compression (enable_fbc)

Making use of Framebuffer compression (FBC) can reduce power consumption while reducing memory bandwidth needed for screen refreshes.

To enable FBC, use i915.enable_fbc=1 as kernel parameter or set in /etc/modprobe.d/i915.conf :

Enabling frame buffer compression on pre-Sandy Bridge CPUs results in endless error messages:

The solution is to disable frame buffer compression which will imperceptibly increase power consumption (around 0.06 W). In order to disable it add i915.enable_fbc=0 to the kernel line parameters. More information on the results of disabled compression can be found here.

Fastboot

The goal of Intel Fastboot is to preserve the frame-buffer as setup by the BIOS or bootloader to avoid any flickering until Xorg has started.[9][10]

To force enable fastboot on platforms where it is not the default already, set i915.fastboot=1 as kernel parameter or set in /etc/modprobe.d/i915.conf :

Intel GVT-g graphics virtualization support

See Intel GVT-g for details.

Tips and tricks

Setting scaling mode

This can be useful for some full screen applications:

where param can be:

• center : resolution will be kept exactly as defined, no scaling will be made,
• full : scale the resolution so it uses the entire screen or
• full_aspect : scale the resolution to the maximum possible but keep the aspect ratio.

If it does not work, try:

where param is one of «Full» , «Center» or «Full aspect» .

Hardware accelerated H.264 decoding on GMA 4500

The libva-intel-driver package only provides hardware accelerated MPEG-2 decoding for GMA 4500 series GPUs. The H.264 decoding support is maintained in a separated g45-h264 branch, which can be used by installing libva-intel-driver-g45-h264 AUR package. Note, however, that this support is experimental and its development has been abandoned. Using the VA-API with this driver on a GMA 4500 series GPU will offload the CPU but may not result in as smooth a playback as non-accelerated playback. Tests using mplayer showed that using vaapi to play back an H.264 encoded 1080p video halved the CPU load (compared to the XV overlay) but resulted in very choppy playback, while 720p worked reasonably well [12]. This is echoed by other experiences [13]. Setting the preallocated video ram size higher in BIOS results in much better hardware decoded playback. Even 1080p h264 works well if this is done. Smooth playback (1080p/720p) works also with mpv-git AUR in combination with ffmpeg-git AUR and libva-intel-driver-g45-h264 AUR . With MPV and the Firefox plugin «Send to MPV player»[14] it is possible to watch hardware accelerated YouTube videos.

Old OpenGL Driver (i965)

As of Mesa 19.2, a new OpenGL driver, Iris, is available for testing. In Mesa 20.0, the Iris driver is promoted to be the default for Gen8+. Certain applications run faster with it. You may disable it and revert to use the old i965 driver by setting the MESA_LOADER_DRIVER_OVERRIDE=i965 environment variable before starting any OpenGL application. This setting does not affect Vulkan applications.

Overriding reported OpenGL version

The MESA_GL_VERSION_OVERRIDE environment variable can be used to override the reported OpenGL version to any application. For example, setting MESA_GL_VERSION_OVERRIDE=4.5 will report OpenGL 4.5.

Setting brightness and gamma

Troubleshooting

Tearing

The SNA acceleration method causes tearing on some machines. To fix this, enable the TearFree option in the driver by adding the following line to your configuration file:

See the original bug report for more info.

Disable Vertical Synchronization (VSYNC)

• Chomium/Chrome has lags and slow performance due to GPU and runs smoothly with —disable-gpu switch
• glxgears test does not show desired performance

The intel-driver uses Triple Buffering for vertical synchronization; this allows for full performance and avoids tearing. To turn vertical synchronization off (e.g. for benchmarking) use this .drirc in your home directory:

DRI3 issues

DRI3 is the default DRI version in xf86-video-intel . On some systems this can cause issues such as this. To switch back to DRI2 add the following line to your configuration file:

For the modesetting driver, this method of disabling DRI3 does not work. Instead, one can set the environment variable LIBGL_DRI3_DISABLE=1 .

Font and screen corruption in GTK applications (missing glyphs after suspend/resume)

Should you experience missing font glyphs in GTK applications, the following workaround might help. Edit /etc/environment to add the following line:

Blank screen during boot, when «Loading modules»

If using «late start» KMS and the screen goes blank when «Loading modules», it may help to add i915 and intel_agp to the initramfs. See Kernel mode setting#Early KMS start section.

Alternatively, appending the following kernel parameter seems to work as well:

If you need to output to VGA then try this:

X freeze/crash with intel driver

Some issues with X crashing, GPU hanging, or problems with X freezing, can be fixed by disabling the GPU usage with the NoAccel option — add the following lines to your configuration file:

Alternatively, try to disable the 3D acceleration only with the DRI option:

Baytrail complete freeze

If you are using kernel > 3.16 on Baytrail architecture and randomly encounter total system freezes, the following kernel option is a workaround until this bug is fixed in the linux kernel.

This is originally an Intel CPU bug that can be triggered by certain c-state transitions. It can also happen with Linux kernel 3.16 or Windows, though apparently much more rarely. The kernel option will prevent the freeze by avoiding c-state transitions but will also increase power consumption.

Adding undetected resolutions

This issue is covered on the Xrandr page.

Backlight is not adjustable

If after resuming from suspend, the hotkeys for changing the screen brightness do not take effect, check your configuration against the Backlight article.

If the problem persists, try one of the following kernel parameters:

Also make sure you are not using fastboot mode (i915.fastboot kernel parameter), it is known for breaking backlight controls.

Corruption or unresponsiveness in Chromium and Firefox

If you experience corruption, unresponsiveness, lags or slow performance in Chromium and/or Firefox some possible solutions are:

Kernel crashing w/kernels 4.0+ on Broadwell/Core-M chips

A few seconds after X/Wayland loads the machine will freeze and journalctl will log a kernel crash referencing the Intel graphics as below:

This can be fixed by disabling execlist support which was changed to default on with kernel 4.0. Add the following kernel parameter:

This is known to be broken to at least kernel 4.0.5.

Lag in Windows guests

The video output of a Windows guest in VirtualBox sometimes hangs until the host forces a screen update (e.g. by moving the mouse cursor). Removing the enable_fbc=1 option fixes this issue.

Screen flickering

Panel Self Refresh (PSR), a power saving feature used by Intel iGPUs is known to cause flickering in some instances FS#49628 FS#49371 FS#50605. A temporary solution is to disable this feature using the kernel parameter i915.enable_psr=0 .

OpenGL 2.1 with i915 driver

The update of mesa from version 13.x to 17 may break support for OpenGL 2.1 on third gen Intel GPUs (GMA3100, see here), as described in this article, reverting it back to OpenGL 1.4. However this could be restored manually by setting /etc/drirc or

/.drirc options like:

KMS Issue: console is limited to small area

One of the low-resolution video ports may be enabled on boot which is causing the terminal to utilize a small area of the screen. To fix, explicitly disable the port with an i915 module setting with video=SVIDEO-1:d in the kernel command line parameter in the bootloader. See Kernel parameters for more info.

If that does not work, try disabling TV1 or VGA1 instead of SVIDEO-1. Video port names can be listed with xrandr.

Weathered colors (color range problems)

The «Broadcast RGB» property in the Intel driver defines the color range which can be used by the display — either «Limited 16:235» (which limits the color range for some displays that cannot properly process full range color signals) and «Full». Since kernel 3.9, the new default property «Automatic» tries to determine whenever the display supports the full color range, and if it does not/detection fails, color range falls back to «Limited 16:235». If detections faulty falls back to limited color range, it results in weathered colors and grey blacks. On some displays/connectors, despite the full color range being supported properly, automatic detection fails and falls back to the limited color range (upstream bug report, kernels 4.18-4.20).

You can forcefully set the desired color range by running xrandr —output —set «Broadcast RGB» «Full» (replace with the appropriate output device, listed by running xrandr ). There is no way to persist this setting in xorg.conf .

No sound through HDMI on a Haswell CPU

According to a Linux kernel issue, sound will not be output through HDMI if intel_iommu=on . To fix this problem, use the following kernel parameter:

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