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Created September 1, 2023 22:59
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This gist will show you how to tune your Intel-based Skylake, Kabylake and beyond Integrated Graphics Core for performance and reliability through GuC and HuC firmware usage on Linux.
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skylake-tuning-linux.md

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:

See the supported module options:

Let's see if the features we're after are supported:

sudo modinfo i915 | egrep -i "guc|huc|dmc"

firmware:       i915/bxt_dmc_ver1_07.bin
firmware:       i915/skl_dmc_ver1_27.bin
firmware:       i915/kbl_dmc_ver1_04.bin
firmware:       i915/glk_dmc_ver1_04.bin
firmware:       i915/cnl_dmc_ver1_07.bin
firmware:       i915/icl_dmc_ver1_07.bin
firmware:       i915/kbl_guc_ver9_39.bin
firmware:       i915/bxt_guc_ver9_29.bin
firmware:       i915/skl_guc_ver9_33.bin
firmware:       i915/kbl_huc_ver02_00_1810.bin
firmware:       i915/bxt_huc_ver01_8_2893.bin
firmware:       i915/skl_huc_ver01_07_1398.bin
parm:           enable_guc:Enable GuC load for GuC submission and/or HuC load. Required functionality can be selected using bitmask values. (-1=auto, 0=disable [default], 1=GuC submission, 2=HuC load) (int)
parm:           guc_log_level:GuC firmware logging level. Requires GuC to be loaded. (-1=auto [default], 0=disable, 1..4=enable with verbosity min..max) (int)
parm:           guc_firmware_path:GuC firmware path to use instead of the default one (charp)
parm:           huc_firmware_path:HuC firmware path to use instead of the default one (charp)
parm:           dmc_firmware_path:DMC firmware path to use instead of the default one (charp)

Note: The intel_pstate driver is the default since Linux 4.10 on SKL+. Thanks for the updates on this @pcordes and the correction on module options syntax in /etc/modprobe.d/i915.conf, @vinzent. Gr33ts ;-)

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

Then rebuild initramfs:

On Fedora:

dracut --force

On Debian-based distributions:

Simply run:

sudo update-initramfs

update-grub

Then reboot.

Your modern Intel HD Graphics 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=3

Other safe options to pass are enable_fbc=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_fbc=1 enable_guc=3

On Linux 4.16+, GuC firmware loading and submission is now handled by the enable_guc parameter in place of the former enable_guc_loading=1 and enable_guc_submission=1 parameters. Adjust as needed.

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_dc 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"

This is not needed on server-grade SKUs where Xorg is unwelcome.

Debugging:

Simply inspect dmesg:

dmesg | grep drm

And also look at the output of:

journalctl -b -o short-monotonic -k

To confirm that the settings you wanted have been applied, run:

dmesg | grep -iE "huc|guc|dmc"

Output may look like this:

[    2.014699] Setting dangerous option enable_guc - tainting kernel
[    2.019971] [drm] Finished loading DMC firmware i915/kbl_dmc_ver1_04.bin (v1.4)
[    2.030651] [drm] HuC: Loaded firmware i915/kbl_huc_ver02_00_1810.bin (version 2.0)
[    2.040648] [drm] GuC: Loaded firmware i915/kbl_guc_ver9_39.bin (version 9.39)
[    2.051850] i915 0000:00:02.0: GuC firmware version 9.39
[    2.051850] i915 0000:00:02.0: GuC submission enabled
[    2.051851] i915 0000:00:02.0: HuC enabled

Which means you're good to go.

You can also take a look at:

  1. GuC load status:
sudo cat /sys/kernel/debug/dri/0/i915_guc_load_status
GuC firmware: i915/kbl_guc_ver9_39.bin
	status: fetch SUCCESS, load SUCCESS
	version: wanted 9.39, found 9.39
	header: offset 0, size 128
	uCode: offset 128, size 147392
	RSA: offset 147520, size 256

GuC status 0x800330ec:
	Bootrom status = 0x76
	uKernel status = 0x30
	MIA Core status = 0x3

Scratch registers:
	 0: 	0xf0000000
	 1: 	0x1
	 2: 	0xc
	 3: 	0x0
	 4: 	0x2
	 5: 	0x0
	 6: 	0x7f2000
	 7: 	0x8
	 8: 	0x3
	 9: 	0x403240
	10: 	0x0
	11: 	0x0
	12: 	0x0
	13: 	0x0
	14: 	0x0
	15: 	0x0
  1. HuC load status:
sudo cat /sys/kernel/debug/dri/0/i915_huc_load_status
 HuC firmware: i915/kbl_huc_ver02_00_1810.bin
	status: fetch SUCCESS, load SUCCESS
	version: wanted 2.0, found 2.0
	header: offset 0, size 128
	uCode: offset 128, size 218304
	RSA: offset 218432, size 256

HuC status 0x00006080:

Also see: https://01.org/linuxgraphics/downloads/firmware

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

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