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Intel UHD 630 Display Backlight on Sequoia — Dell G3 3579

Why the internal panel goes black at boot on macOS Sequoia, why the brightness keys stop working, and why the configuration here uses -igfxblr.

Symptoms

Configuration Boot Brightness keys
-igfxblt (Sonoma's argument) panel black n/a — cannot test
-igfxblr (this EFI) panel bright do not work (no HUD, no change)

Brightness via the slider / Control Center works with -igfxblr.

Affected configuration

  • Intel UHD Graphics 630 (8086:3E9B, Coffee Lake-H), eDP panel driven by the iGPU
  • macOS Sequoia 15.8.2 (AppleBacklight 180.12)
  • WhateverGreen backlight registers fixes

Cause

macOS 15 (AppleBacklight 180.12) requires the WhateverGreen backlight-registers fix to initialise the eDP backlight:

  • -igfxblt — the alternative registers fix — works on Sonoma (AppleBacklight 180.9) but does not initialise the panel on Sequoia. The boot logo renders, then the panel goes dark as the kernel takes over.
  • -igfxblr — the classic Backlight Registers Fix for KBL/CFL/ICL — lights the panel correctly.

The same registers fix that lights the panel also disables the ACPI brightness-key path: BrightnessKeys performs its adjustment through the standard ACPI backlight methods, which -igfxblr overrides. Measured with an in-boot sampler (AppleBacklightDisplay → bklt): the value does not change on key press with -igfxblr, on a panel that lights correctly.

Firmware side (verified from the DSDT)

The Dell EC handles brightness through a single query method, _Q66, which routes to NEVT and then to \_SB.PCI0.LPCB.ECDV.VGBI.VBDS — a vendor-specific brightness method. The DSDT emits the standard ACPI Video-Extension notifications to the display device:

Notify(\_SB.PCI0.GFX0.LCD_, 0x86)   // increase brightness
Notify(\_SB.PCI0.GFX0.LCD_, 0x87)   // decrease brightness

So the firmware does its part. The failure is in macOS 15's handling of those notifications when the registers fix is active.

Solution

Use -igfxblr and accept the brightness-key trade-off. Everything else that was tested and rejected is documented below.

Tested and rejected

Change Result
Full ACPI/kext parity with the working Sonoma EFI (SSDT-ALSD, SMCLightSensor, exact Sonoma boot-args) panel still black with -igfxblt; keys still dead with -igfxblr
Aligning com.apple.keyboard.fnState with Sonoma no effect on keys
hidutil remap of F11/F12 to brightness usages no effect — the keys are ACPI EC events, not HID events
Re-enabling the USB map fixed Bluetooth (unrelated), keys unaffected

A manual bklt reading showed the driver value stays at its maximum while the panel is dark — macOS requests full brightness and the hardware does not follow, a register-path failure rather than a policy problem.

Applicability to other systems

This applies to Coffee Lake laptops whose panel is driven by the iGPU and whose EC handles brightness in firmware. The working argument depends on the macOS release: -igfxblt was introduced for the 13.4 regression on CFL and still works on Sonoma here; Sequoia needs -igfxblr. Other machines may differ — measure, do not copy.

References