** Changed in: linux (Ubuntu Noble)
Importance: Undecided => Medium
** Changed in: linux (Ubuntu Noble)
Status: In Progress => Fix Committed
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https://bugs.launchpad.net/bugs/2136958
Title:
Random flickering with Intel i915 (CoffeeLake and WhiskeyLake) on
Linux 6.8
Status in linux package in Ubuntu:
In Progress
Status in linux source package in Noble:
Fix Committed
Status in linux source package in Questing:
In Progress
Status in linux source package in Resolute:
In Progress
Bug description:
SRU Justification
[Impact]
Systems with Intel CoffeeLake (CFL) and WhiskeyLake (WHL) integrated graphics experience screen flickering issues when running Ubuntu kernel 6.8.0-x.
The issue occurs because:
1. Ubuntu kernel configuration enables CONFIG_INTEL_IOMMU_DEFAULT_ON and CONFIG_INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON by default (commit 77e530c1a864c)
2. These Intel integrated graphics generations have compatibility issues with DMAR (DMA Remapping) enabled
3. The interaction between IOMMU scalable mode and the i915 graphics driver causes intermittent display flickering
This is part of a broader issue affecting multiple Intel integrated
graphics generations (Skylake, KabyLake, CoffeeLake, WhiskeyLake, and
CometLake) as documented in the upstream bug report. Previous patches
have already addressed SKL, KBL, and CML; this patch completes the
series by adding CFL and WHL.
Affected hardware: Systems with Intel CoffeeLake or WhiskeyLake
integrated graphics (device IDs: 0x3E90-0x3E9C, 0x3EA0-0x3EA9)
[Fix]
Single UBUNTU SAUCE patch adds CFL and WHL device IDs to the IOMMU quirk list:
UBUNTU: SAUCE: iommu/intel: disable DMAR for CFL and WHL integrated gfx
- Adds 16 CoffeeLake device IDs (CFL_S, CFL_H, CFL_U variants)
- Adds 5 WhiskeyLake device IDs (WHL_U variants)
- Follows the same pattern as previous SKL/KBL/CML quirk patches
- Device IDs sourced from include/drm/i915_pciids.h for completeness
This is an Ubuntu-specific SAUCE patch as upstream has not yet
provided a proper fix. The quirk approach is used temporarily until a
proper upstream solution is available.
Previous related commits in this series:
- fe35c48a46619 "UBUNTU: SAUCE: iommu/intel: disable DMAR for SKL integrated gfx"
- 69a3b8e5f6ebd "UBUNTU: SAUCE: iommu/intel: disable DMAR for KBL and CML integrated gfx"
[Test Plan]
Test on hardware with CoffeeLake or WhiskeyLake integrated graphics:
1. Identify if the system has affected hardware:
```
lspci -nn | grep VGA
```
Look for Intel graphics with device IDs in the 0x3E90-0x3EA9 range.
2. Reproduce the flickering (before the fix):
a. Boot with kernel 6.8.0-x without the patch
b. Move windows around or trigger compositor effects
c. Observe intermittent screen flickering or tearing
3. Verify the fix:
a. Boot with kernel containing the patch
b. Check that IOMMU is bypassed for the graphics device:
```
sudo dmesg | grep -i "Disabling IOMMU for graphics on this chipset"
```
c. Should see: "Disabling IOMMU for graphics on this chipset"
d. Verify no flickering occurs during video playback and window animations
e. Confirm graphics performance remains normal
[Where problems could occur]
The changes affect the Intel IOMMU driver initialization for CoffeeLake and WhiskeyLake integrated graphics only.
Potential issues:
1. **Security reduction**: Disabling DMAR for integrated graphics
removes IOMMU protection for GPU DMA operations. However, integrated
graphics are generally trusted components, and the security impact is
minimal compared to the usability impact of screen flickering.
2. **Hardware-specific behavior**: Some CFL/WHL systems might not
exhibit the flickering issue, and for those systems, this patch
unnecessarily disables IOMMU for graphics. However, the functional
impact is negligible, and disabling DMAR has no negative performance
implications.
3. **Interaction with other IOMMU features**: The quirk only affects
the integrated graphics device. Other IOMMU functionality (ATS,
interrupt remapping, etc.) remains unaffected.
The impact is limited to the IOMMU configuration for CoffeeLake and
WhiskeyLake integrated graphics. All other system components continue
to benefit from IOMMU protection.
[Other Info]
This is an Ubuntu SAUCE patch (not upstream) that works around the issue until a proper upstream fix is available.
Upstream tracking bug:
https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/11504
The issue was introduced in Ubuntu 6.8 kernel by commit:
77e530c1a864c "UBUNTU: [Config] enable Intel DMA remapping by default"
This patch completes a series of quirks for affected Intel graphics generations:
1. Skylake (SKL) - fe35c48a46619
2. KabyLake (KBL) and CometLake (CML) - 69a3b8e5f6ebd
3. CoffeeLake (CFL) and WhiskeyLake (WHL) - this patch
All affected device IDs were verified against the upstream i915
driver's device ID definitions in include/drm/i915_pciids.h.
======================================
Random flickering of the screen when cursor is in the lower part of
the screen. The flickering stops when mouse is again moved.
This problem happens on my two laptops (CoffeeLake and WhiskeyLake), details below. Adding
intel_iommu=igfx_off to kernel command line solves this problem.
Bug https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2062951/+index?comments=all solves the problem for some architectures, but it is now closed. Hence I opened new bug report.
Laptop 1:
$ lspci -nnk | grep -A3 VGA
00:02.0 VGA compatible controller [0300]: Intel Corporation CoffeeLake-H GT2 [UHD Graphics 630] [8086:3e9b]
DeviceName: Onboard IGD
Subsystem: Hewlett-Packard Company CoffeeLake-H GT2 [UHD Graphics 630] [103c:8427]
Kernel driver in use: i915
--
01:00.0 VGA compatible controller [0300]: NVIDIA Corporation GP107GLM [Quadro P1000 Mobile] [10de:1cbb] (rev a1)
Subsystem: Hewlett-Packard Company GP107GLM [Quadro P1000 Mobile] [103c:8427]
Kernel driver in use: nvidia
Kernel modules: nvidiafb, nouveau, nvidia_drm, nvidia
# System Details Report
---
## Report details
- **Date generated:** 2025-11-24 21:29:40
## Hardware Information:
- **Hardware Model:** HP HP ZBook Studio G5
- **Memory:** 16.0 GiB
- **Processor:** Intel® Core™ i7-8750H × 12
- **Graphics:** Intel® UHD Graphics 630 (CFL GT2)
- **Graphics 1:** Quadro P1000
- **Disk Capacity:** 512.1 GB
## Software Information:
- **Firmware Version:** Q71 Ver. 01.32.00
- **OS Name:** Ubuntu 24.04.3 LTS
- **OS Build:** (null)
- **OS Type:** 64-bit
- **GNOME Version:** 46
- **Windowing System:** X11
- **Kernel Version:** Linux 6.8.0-88-generic
Laptop 2:
$ lspci -nnk | grep -A3 VGA
00:02.0 VGA compatible controller [0300]: Intel Corporation WhiskeyLake-U GT2 [UHD Graphics 620] [8086:3ea0] (rev 02)
Subsystem: Lenovo WhiskeyLake-U GT2 [UHD Graphics 620] [17aa:2281]
Kernel driver in use: i915
Kernel modules: i915
# System Details Report
---
## Report details
- **Date generated:** 2025-11-26 14:28:35
## Hardware Information:
- **Hardware Model:** Lenovo ThinkPad P53s
- **Memory:** 40.0 GiB
- **Processor:** Intel® Core™ i7-8565U × 8
- **Graphics:** Intel® UHD Graphics 620 (WHL GT2)
- **Graphics 1:** NV138
- **Disk Capacity:** 1.0 TB
## Software Information:
- **Firmware Version:** N2IETA6W (1.84 )
- **OS Name:** Ubuntu 24.04.3 LTS
- **OS Build:** (null)
- **OS Type:** 64-bit
- **GNOME Version:** 46
- **Windowing System:** X11
- **Kernel Version:** Linux 6.8.0-88-generic
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