Public bug reported:
## 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
```
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2154351
Title:
i915 HDMI: External monitor randomly flickers/power cycles -
regression across multiple Intel GPU generations
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