Cannot set backlight on Linux 5.11.16

Changing backlight does not reflect on the display. It does show on dmesg that the brightness is being updated.

Note that it does work but requires i915.enable_dpcd_backlight=1 to be set when running on Linux 5.10.37.

When using acpilight and xbacklight -set 10:

sudo dmesg | grep "backlight"
[  342.199776] [drm:intel_backlight_device_update_status [i915]] updating intel_backlight, brightness=6000/60000
[  342.199843] i915 0000:00:02.0: [drm:intel_backlight_device_update_status [i915]] set backlight level = 9176

Setting to lower values does not actually reflect the backlight on the display.

When using acpilight and xbacklight -set 0:

sudo dmesg | grep "backlight"
[  544.123553] [drm:intel_backlight_device_update_status [i915]] updating intel_backlight, brightness=0/60000
[  544.123619] i915 0000:00:02.0: [drm:intel_backlight_device_update_status [i915]] set backlight level = 3529
[  544.123698] i915 0000:00:02.0: [drm:intel_pps_backlight_power [i915]] panel power control backlight disable

Attached below is the dmesg booted with these kernel parameters.

i915.enable_dpcd_backlight=1 drm.debug=0x1e log_buf_len=1M

dmesg_enable_dpcd.log

dmesg_no_dpcd.log

dmesg_lts_dpcd.log

uname -m
x86_64

uname -r
5.12.4-arch1-2

Machine: Clevo N850EP6

lspci -nnk
00:00.0 Host bridge [0600]: Intel Corporation 8th Gen Core Processor Host Bridge/DRAM Registers [8086:3ec4] (rev 07)
	DeviceName: Onboard - Other
	Subsystem: CLEVO/KAPOK Computer Device [1558:8500]
	Kernel driver in use: skl_uncore
00:01.0 PCI bridge [0604]: Intel Corporation 6th-9th Gen Core Processor PCIe Controller (x16) [8086:1901] (rev 07)
	Kernel driver in use: spaceport
00:02.0 VGA compatible controller [0300]: Intel Corporation UHD Graphics 630 (Mobile) [8086:3e9b]
	DeviceName: Onboard - Video
	Subsystem: CLEVO/KAPOK Computer Device [1558:8500]
	Kernel driver in use: i915
	Kernel modules: i915
00:08.0 System peripheral [0880]: Intel Corporation Xeon E3-1200 v5/v6 / E3-1500 v5 / 6th/7th/8th Gen Core Processor Gaussian Mixture Model [8086:1911]
	DeviceName: Onboard - Other
	Subsystem: CLEVO/KAPOK Computer Device [1558:8500]
00:12.0 Signal processing controller [1180]: Intel Corporation Cannon Lake PCH Thermal Controller [8086:a379] (rev 10)
	DeviceName: Onboard - Other
	Subsystem: CLEVO/KAPOK Computer Device [1558:8500]
	Kernel driver in use: intel_pch_thermal
	Kernel modules: intel_pch_thermal
00:14.0 USB controller [0c03]: Intel Corporation Cannon Lake PCH USB 3.1 xHCI Host Controller [8086:a36d] (rev 10)
	DeviceName: Onboard - Other
	Subsystem: CLEVO/KAPOK Computer Device [1558:8500]
	Kernel driver in use: xhci_hcd
	Kernel modules: xhci_pci
00:14.2 RAM memory [0500]: Intel Corporation Cannon Lake PCH Shared SRAM [8086:a36f] (rev 10)
	DeviceName: Onboard - Other
	Subsystem: Intel Corporation Device [8086:7270]
00:16.0 Communication controller [0780]: Intel Corporation Cannon Lake PCH HECI Controller [8086:a360] (rev 10)
	DeviceName: Onboard - Other
	Subsystem: CLEVO/KAPOK Computer Device [1558:8500]
	Kernel driver in use: mei_me
	Kernel modules: mei_me
00:17.0 SATA controller [0106]: Intel Corporation Cannon Lake Mobile PCH SATA AHCI Controller [8086:a353] (rev 10)
	DeviceName: Onboard - SATA
	Subsystem: CLEVO/KAPOK Computer Device [1558:8500]
	Kernel driver in use: ahci
00:1d.0 PCI bridge [0604]: Intel Corporation Cannon Lake PCH PCI Express Root Port #9 [8086:a330] (rev f0)
	Kernel driver in use: pcieport
00:1d.5 PCI bridge [0604]: Intel Corporation Cannon Lake PCH PCI Express Root Port #14 [8086:a335] (rev f0)
	Kernel driver in use: pcieport
00:1d.6 PCI bridge [0604]: Intel Corporation Cannon Lake PCH PCI Express Root Port #15 [8086:a336] (rev f0)
	Kernel driver in use: pcieport
00:1f.0 ISA bridge [0601]: Intel Corporation HM470 Chipset LPC/eSPI Controller [8086:a30d] (rev 10)
	DeviceName: Onboard - Other
	Subsystem: CLEVO/KAPOK Computer Device [1558:8500]
00:1f.3 Audio device [0403]: Intel Corporation Cannon Lake PCH cAVS [8086:a348] (rev 10)
	DeviceName: Onboard - Sound
	Subsystem: CLEVO/KAPOK Computer Device [1558:8500]
	Kernel driver in use: snd_hda_intel
	Kernel modules: snd_hda_intel, snd_soc_skl, snd_sof_pci_intel_cnl
00:1f.4 SMBus [0c05]: Intel Corporation Cannon Lake PCH SMBus Controller [8086:a323] (rev 10)
	DeviceName: Onboard - Other
	Subsystem: CLEVO/KAPOK Computer Device [1558:8500]
	Kernel driver in use: i801_smbus
	Kernel modules: i2c_i801
00:1f.5 Serial bus controller [0c80]: Intel Corporation Cannon Lake PCH SPI Controller [8086:a324] (rev 10)
	DeviceName: Onboard - Other
	Subsystem: CLEVO/KAPOK Computer Device [1558:8500]
03:00.0 Network controller [0280]: Intel Corporation Device [8086:2725] (rev 1a)
	Subsystem: Intel Corporation Device [8086:0024]
	Kernel driver in use: iwlwifi
	Kernel modules: iwlwifi
04:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTL8411B PCI Express Card Reader [10ec:5287] (rev 01)
	Subsystem: CLEVO/KAPOK Computer Device [1558:8500]
	Kernel driver in use: rtsx_pci
	Kernel modules: rtsx_pci
04:00.1 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [10ec:8168] (rev 12)
	Subsystem: CLEVO/KAPOK Computer Device [1558:8500]
	Kernel driver in use: r8169
	Kernel modules: r8169

xrandr.log