[Bug 2154351] Re: i915 HDMI: External monitor randomly flickers/power cycles - regression across multiple Intel GPU generations

** Tags added: kernel-daily-bug -- You received this bug notification because you are subscribed to linux in Ubuntu. Matching subscriptions: Bgg, Bmail, Nb https://bugs.launchpad.net/bugs/2154351 Title: i915 HDMI: External monitor randomly flickers/power cycles - regression across multiple Intel GPU generations Status in linux package in Ubuntu: New Bug description: ## Summary External HDMI monitor randomly turns off and on (flickers/power cycles). The issue persists across: - **Two different laptops** (both Acer, both Intel i915 HDMI output) - **Two different monitors** (old monitor + new Xiaomi P270CA) - **Multiple HDMI cables** - **Multiple kernel versions** (6.8 through 7.0.9) - **Two Ubuntu versions** (24.04 with kernel 6.8, 26.04 with kernel 7.0) The problem appeared as a **regression** — the old laptop (Acer, i7-7700HQ/Kaby Lake, Intel HD 630) worked perfectly with external HDMI monitors from 2017 until ~2025, then started flickering after a kernel update. ## Hardware ### System 1 (current) - **Laptop**: Acer, Intel Core i7-13700H (Raptor Lake-P) - **GPU**: Intel UHD Graphics (i915) + NVIDIA RTX 3050 Mobile (unused for display) - **Kernel**: 7.0.9-070009-generic (Ubuntu 26.04, Wayland/GNOME) - **Monitor**: Xiaomi P270CA (27", 2560x1440, HDMI) - **Connection**: HDMI (card1-HDMI-A-1) ### System 2 (old) - **Laptop**: Acer, Intel Core i7-7700HQ (Kaby Lake) - **GPU**: Intel HD 630 (i915) + NVIDIA GTX 1050 Mobile (nouveau) - **Kernel**: 6.8.0-101-generic (Ubuntu 24.04) - **Same monitor, same symptoms** ## Symptoms 1. **Intermittent**: Monitor randomly goes black for 1-2 seconds, then comes back. No pattern — can happen every few seconds or be fine for hours. 2. **Severe symptom** (2026-05-27): Monitor enters continuous on/off cycling loop. Unplugging/replugging HDMI does NOT help. Power cycling the monitor (unplugging DC power cable, waiting, replugging) fixes it temporarily. 3. **No kernel errors**: `dmesg` shows ZERO errors — no HPD events, no FIFO underruns, no disconnect/reconnect, no i915 errors. 4. **DRM debug shows clean page-flips**: Atomic commits contain only PLANE + CRTC state (no connector state). No unnecessary modesets. Kernel is functioning correctly at the DRM level. ## What Has Been Tried (ALL ineffective) ### Kernel parameters: - i915.enable_psr=0 — no effect - i915.enable_dc=0 — no effect - i915.disable_power_well=0 — no effect - i915.enable_panel_replay=0 — no effect - i915.enable_dsb=0 — no effect - i915.enable_dpt=0 — no effect - intel_iommu=igfx_off — no effect ### Other: - Different HDMI cables — no effect - Different monitors — no effect - Different laptops — no effect - Lowering resolution to 1920x1080 — no effect - Lowering refresh rate to 60Hz — no effect - Disabling GNOME DPMS — no effect - xe driver (i915.modeset=0 xe.modeset=1) — HDMI output doesn't work at all with xe ## Key Evidence 1. **Regression**: HDMI worked from 2017 to ~2025 on old laptop. Broke after kernel update. 2. **Cross-hardware**: Persists across two Intel GPU generations (Kaby Lake HD 630 and Raptor Lake UHD), two different Acer laptops, two different monitors, multiple cables. 3. **Silent at kernel level**: Zero dmesg errors during flicker events. Signal drop happens below kernel visibility. 4. **Power cycle recovery**: Only power cycling the monitor restores it from continuous cycling. Monitor's TMDS receiver gets into a bad state. 5. **DisplayPort not yet tested**: DP uses different physical layer — may not have this issue. ## Related Bugs - Launchpad #2148269: Raptor Lake + i915 + HDMI + Wayland atomic modesetting freeze - Launchpad #2086587: Random flickering with Intel i915 on kernel 6.8+ - Launchpad #2136979: External monitor flickers, fix in v6.19-rc1 ## Kernel Command Line ``` BOOT_IMAGE=/boot/vmlinuz-7.0.9-070009-generic root=UUID=... ro quiet splash intel_iommu=igfx_off ``` ## i915 Module Parameters ``` enable_psr=0, enable_dc=0, disable_power_well=0, enable_panel_replay=0, enable_dsb=0, enable_dpt=0 ``` ## EDID ``` Manufacturer: Xiaomi (Mi Monitor) Product code: 0x27B2 Serial: 5745710013614 Native mode: 2560x1440 ``` To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2154351/+subscriptions