Tuning Intel Skylake and beyond for optimal performance and feature level support on Linux:
Note that on Skylake, Kabylake (and the now cancelled "Broxton") SKUs, functionality such as power saving, GPU scheduling and HDMI audio have been moved onto binary-only firmware, and as such, the GuC and the HuC blobs must be loaded at run-time to access this functionality.
Enabling GuC and HuC on Skylake and above requires a few extra parameters be passed to the kernel before boot.
Instructions provided for both Fedora and Ubuntu (including Debian):
Note that the firmware for these GPUs is often packaged by your distributor, and as such, you can confirm the firmware blob's availability by running:
1. On Fedora:
rpm -ql linux-firmware | fgrep i915
Sample output:
/usr/lib/firmware/i915
/usr/lib/firmware/i915/bxt_dmc_ver1_07.bin
/usr/lib/firmware/i915/kbl_dmc_ver1.bin
/usr/lib/firmware/i915/kbl_dmc_ver1_01.bin
/usr/lib/firmware/i915/skl_dmc_ver1_23.bin
/usr/lib/firmware/i915/skl_guc_ver1.bin
/usr/lib/firmware/i915/skl_guc_ver4.bin
/usr/lib/firmware/i915/skl_guc_ver6.bin
/usr/lib/firmware/i915/skl_guc_ver6_1.bin
/usr/share/doc/linux-firmware/LICENSE.i915
2. On Ubuntu:
dpkg -L linux-firmware | fgrep i915
It may be wise to install the linux-firmware-nonfree package as it may contain extra firmware blobs on Ubuntu releases prior to 16.04LTS. Don't install this on 16.04LTS and above.
Now, to the real meat:
GUC loading on Skylake and above:
Add this to the kernel boot parameters on /etc/default/grub:
intel_pstate=skylake_hwp
The intel_pstate=skylake_hwp option enables Intel's Hardware P-States, known commonly by the marketing moniker "SpeedShift".
Note that Intel's IOMMU for VT-d (enabled in the kernel by passing intel_iommu=on to the kernel boot options) cannot be used together with frame buffer compression (i915.enable_fbc=1 argument passed to the i915). Frame Buffer Compression will be disabled automatically to prevent screen tearing in this case.
Then, update grub on Fedora:
(Run commands as root):
For EFI boot (More common):
grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg
And if you're still booting up in legacy BIOS mode on an MBR-style partitioning scheme or with CSM enabled on Fedora for whatever reason:
grub2-mkconfig -o /boot/grub2/grub.cfg
On Ubuntu:
Simply run:
update-grub
Then reboot.
Your Skylake processor graphics will work just fine.
You can also add this to: /etc/modprobe.d/i915.conf
In the following syntax:
options i915.enable_guc_loading=1 i915.enable_guc_submission=1
Other safe options to pass are enable_rc6=1, enable_fbc=1, enable_psr=1, disable_power_well=0 and semaphores=1
Reference:
See modinfo output for i915 for available GuC options:
modinfo i915 | grep guc
Further notes:
A list of all options along with short descriptions and default values can be generated with the following command:
$ modinfo -p i915
To check which options are currently enabled, run:
# systool -m i915 -av
You will note that many options default to -1, resulting in per-chip power-saving defaults. It is however possible to configure more aggressive powersaving by using module options. Warning: Diverting from the defaults will mark the kernel as tainted from Linux 3.18 onwards. This basically implies using other options than the per-chip defaults is considered experimental and not supported by the developers.
The following set of options should be generally safe to enable:
/etc/modprobe.d/i915.conf
options i915.enable_rc6=1 i915.enable_fbc=1 i915.semaphores=1
RC6 sleep modes (enable_rc6):
You can experiment with higher values for enable_rc6, but your GPU may not support them or the activation of the other options:
The available enable_rc6 values are a bitmask with bit values RC6=1, RC6p=2, RC6pp=4[4] - where "RC6p" and "RC6pp" are lower power states.
To confirm the current running RC6 level, you can look in sysfs:
# cat /sys/class/drm/card0/power/rc6_enable
If the value read is a lower number than expected, the other RC6 level are probably not supported. Passing drm.debug=0xe to the kernel boot options will add DRM debugging information to the kernel log - possibly including a line like this:
[drm:sanitize_rc6_option] Adjusting RC6 mask to 1 (requested 7, valid 1)
Framebuffer compression (enable_fbc):
Framebuffer compression may be unreliable or unavailable on Intel GPU generations before Sandy Bridge (generation 6). This results in messages logged to the system journal similar to this one:
kernel: drm: not enough stolen space for compressed buffer, disabling.
Tear-free video:
With the SNA acceleration method enabled, tearing may be observed. To fix this, enable the "TearFree" option in the driver by adding the following line to your xorg.conf (or ideally, a sub-configuration file under xorg.conf.d) configuration file:
Option "TearFree" "true"
Debugging:
Simply inspect dmesg:
dmesg | grep drm
And also look at the output of:
journalctl -b -o short-monotonic -k
Screen corruption observed when waking up from suspend
This is often observed as 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:
/etc/environment
COGL_ATLAS_DEFAULT_BLIT_MODE=framebuffer
See this bug here for more details.
Thanks and regards,
Brainiarc7