Flicker Resolved with intel_iommu=igfx_off on ThinkPad T490 (UHD Graphics 620)
Hello everyone, I wanted to report that I’ve successfully resolved the screen flickering issue on my Lenovo ThinkPad T490 with Intel UHD Graphics 620. The flickering occurred across the entire GNOME interface in Wayland, particularly when clicking in the bottom-right area (~1740,1030 on 1920x1080), and was accompanied by "CPU pipe A FIFO underrun" errors in the logs (sudo dmesg | grep -i i915). I’m using Ubuntu 24.04.3 LTS with kernel 6.14.0-1012-oem. Initially, I tried i915.enable_psr=0 and i915.enable_fbc=0 without success. Then, following suggestions, I added intel_iommu=igfx_off to GRUB_CMDLINE_LINUX_DEFAULT (resulting in "quiet splash i915.enable_psr=0 i915.enable_fbc=0 intel_iommu=igfx_off"), ran sudo update-grub, and rebooted. Since then, I haven’t experienced any flickering, even after several hours of use and repeated clicks in the affected area. The current logs (sudo dmesg | grep -i i915) show no FIFO underrun errors or significant warnings after the change. I’m using only the built-in display at 1920x1080, 60 Hz, with 100% scaling. The previous i915_hpd_poll_init_work hogged CPU warnings seem to have disappeared in this log capture, which might indicate overall stabilization. I hope this solution helps other users with similar hardware. Thanks to the community for the support! Recent logs: [ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-6.14.0-1012-oem root=UUID=16a43dc7-79f5-4e8b-9bbd-1eb5c40705ee ro quiet splash i915.enable_psr=0 i915.enable_fbc=0 intel_iommu=igfx_off vt.handoff=7 [ 0.082613] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-6.14.0-1012-oem root=UUID=16a43dc7-79f5-4e8b-9bbd-1eb5c40705ee ro quiet splash i915.enable_psr=0 i915.enable_fbc=0 intel_iommu=igfx_off vt.handoff=7 [ 4.353070] i915 0000:00:02.0: enabling device (0006 -> 0007) [ 4.353878] i915 0000:00:02.0: [drm] Found coffeelake/ult (device ID 3ea0) integrated display version 9.00 stepping N/A [ 4.375317] i915 0000:00:02.0: vgaarb: deactivate vga console [ 4.386565] i915 0000:00:02.0: vgaarb: VGA decodes changed: olddecodes=io+mem,decodes=io+mem:owns=mem [ 4.389087] i915 0000:00:02.0: [drm] Finished loading DMC firmware i915/kbl_dmc_ver1_04.bin (v1.4) [ 4.439481] mei_hdcp 0000:00:16.0-b638ab7e-94e2-4ea2-a552-d1c54b627f04: bound 0000:00:02.0 (ops i915_hdcp_ops [i915]) [ 4.493588] [drm] Initialized i915 1.6.0 for 0000:00:02.0 on minor 1 [ 4.549156] fbcon: i915drmfb (fb0) is primary device [ 4.549163] i915 0000:00:02.0: [drm] fb0: i915drmfb frame buffer device [ 4.631892] snd_hda_intel 0000:00:1f.3: bound 0000:00:02.0 (ops i915_audio_component_bind_ops [i915]) -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux-hwe-6.8 in Ubuntu. https://bugs.launchpad.net/bugs/2062951 Title: Random flickering with Intel i915 (Gen9 GPUs in 6th-8th gen CPUs) on Linux 6.8 Status in Linux: New Status in linux package in Ubuntu: Fix Released Status in linux-hwe-6.8 package in Ubuntu: Fix Released Status in linux source package in Jammy: Confirmed Status in linux-hwe-6.8 source package in Jammy: Fix Released Status in linux source package in Noble: Fix Released Status in linux-hwe-6.8 source package in Noble: Fix Released Status in linux source package in Oracular: Fix Released Status in linux-hwe-6.8 source package in Oracular: Fix Released Bug description: SRU Justification [Impact] The flickering predominantly occurs when the mouse cursor is in the bottom quarter of the screen and stops when the cursor leaves this area. Extensive testing across various kernel versions revealed that the issue became apparent from kernel version 6.8.0 onward, correlating with the mentioned configuration changes, CONFIG_INTEL_IOMMU_DEFAULT_ON and CONFIG_INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON. The problem persists in the latest drm tip. [Fix] As an immediate workaround, adding 'intel_iommu=igfx_off' to the kernel command line has been found to effectively eliminate the flickering issue. This patch proposes the same behavior as 'intel_iommu=igfx_off' and apply the rule to all Intel SKL GPU IDs. [Test] 1. Boot up to desktop with 6.8.0-x kernels 2. Moving cursor around the desktop 3. There should be no flicker while cursor is moving [Where problems could occur] For virtualized environments using hardware-assisted virtualization for graphics (such as VFIO or mediated pass-through), disabling IOMMU for graphics could either disable these features or reduce their security and efficiency. Usually, users pass the 'intel_iommu=on' by themselves when they are using related features. So, the impact of this change is minimal. =========== After migrating Mantic 23.10 install to Linux 6.8.0, I am experiencing heavy flickering at random. It happens after a moderate to heavy on screen activity like window switching, scrolling etc. It never happens when playing video or when there is no interaction using keyboard/pointer. It tend to happen when the mouse cursor is in the bottom quarter of the screen and stops immediately when the cursor leaves that screen region. Around the same time the following appears in kernel log: kernel: i915 0000:00:02.0: [drm] *ERROR* CPU pipe A FIFO underrun Happens on both X11 and Wayland on both KDE plasma and Mate (though less). I first encountered the issue with Linux 6.8.0-11 and it still happens with Ubunutu's 6.8.0-28 and Mainline 6.8.7. Kernels 6.6, 6.5, 6.1 and older did not have that issue. Hardware is: Dell XPS 9350, Vendor Intel, Driver i915, Skylake GT2 [HD Graphics 520] Software: Ubuntu 23.10, KDE Plasma 5.27.10 / Mate 1.26 Attaching kernel log for 6.8.0-28 To manage notifications about this bug go to: https://bugs.launchpad.net/linux/+bug/2062951/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
