[Bug 2172563] Re: [IPU7] Stale 64-byte cache lines in captured frames (colored horizontal dashes on motion) - please backport "media: staging/ipu7: Synchronize capture buffers at the vb2 boundaries"

** 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/2172563 Title: [IPU7] Stale 64-byte cache lines in captured frames (colored horizontal dashes on motion) - please backport "media: staging/ipu7: Synchronize capture buffers at the vb2 boundaries" Status in linux package in Ubuntu: New Bug description: On a Lenovo ThinkPad X9-15 Gen 1 (Intel Core Ultra 7 258V, Lunar Lake, IPU7 8086:645d, Sony IMX471 sensor), the built-in camera works through libcamera, but frames contain short colored horizontal dashes wherever the image changes between frames, for example when moving a hand quickly in front of the camera. A static scene looks clean. Analysis: - Most full-length dashes are exactly 32 pixels wide and aligned to 32-pixel boundaries of the raw frame. With 10-bit Bayer stored in 16-bit containers, that is 64 bytes, i.e. one CPU cache line. - The artifacts appear with libcamera's software ISP in both GPU mode and CPU mode (LIBCAMERA_SOFTISP_MODE=cpu), so they are already present in the raw buffer delivered by intel-ipu7-isys. - This matches the patch "media: staging/ipu7: Synchronize capture buffers at the vb2 boundaries" (LKML, August 2026). It explains that dma_sync_sgtable_for_{cpu,device}() perform no cache maintenance on x86, so stale cached frame data from an earlier buffer slot survives buffer handoff. The patch calls ipu7_dma_sync_sgtable() from buf_prepare and buf_finish. https://ratatoskr.run/lkml/2026/08/17455941 Steps to reproduce: 1. Open GNOME Snapshot (or `cam -c1 --capture` / any libcamera client). 2. Move a hand quickly in front of the camera and take a photo. 3. Observe colored 32-pixel horizontal dashes along moving edges. Expected: clean frames without mixed-in data from earlier frames. Versions: - Ubuntu 26.10, kernel 7.3.0-9-generic (also not fixed in the 7.3.0-10.10 changelog) - libcamera 0.7.0-1ubuntu2 (simple pipeline handler, software ISP) - Machine: ThinkPad X9-15 Gen 1 (21Q60068BM), BIOS N4CET46W (1.22) Request: please consider backporting the above patch (or the merged upstream equivalent) to the Ubuntu kernel's staging ipu7 driver. ProblemType: Bug DistroRelease: Ubuntu 26.10 Package: linux-image-7.3.0-9-generic 7.3.0-9.9 ProcVersionSignature: Ubuntu 7.3.0-9.9-generic 7.3.0-rc6 Uname: Linux 7.3.0-9-generic x86_64 ApportVersion: 2.36.0-0ubuntu1 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: milen 3926 F.... pipewire milen 20413 F.... wireplumber /dev/snd/seq: milen 3926 F.... pipewire CasperMD5CheckResult: pass CurrentDesktop: ubuntu:GNOME Date: Fri Oct 30 00:20:23 2026 InstallationDate: Installed on 2026-10-26 (3 days ago) InstallationMedia: Ubuntu 26.04.1 LTS "Resolute Raccoon" - Release amd64 (20260826) MachineType: LENOVO 21Q60068BM ProcEnviron: LANG=en_US.UTF-8 PATH=(custom, no user) SHELL=/bin/bash TERM=xterm-256color XDG_RUNTIME_DIR=<set> ProcFB: 0 xedrmfb ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-7.3.0-9-generic root=UUID=4a259af1-cc51-483b-bfd7-f0aec4937876 ro quiet splash crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M SourcePackage: linux StagingDrivers: intel_ipu7_isys intel_ipu7 UpgradeStatus: Upgraded to stonking on 2026-10-28 (1 days ago) dmi.bios.date: 08/14/2026 dmi.bios.release: 1.22 dmi.bios.vendor: LENOVO dmi.bios.version: N4CET46W (1.22 ) dmi.board.asset.tag: Not Available dmi.board.name: 21Q60068BM dmi.board.vendor: LENOVO dmi.board.version: SDK0T76576 WIN dmi.chassis.asset.tag: No Asset Information dmi.chassis.type: 10 dmi.chassis.vendor: LENOVO dmi.chassis.version: None dmi.ec.firmware.release: 1.15 dmi.modalias: dmi:bvnLENOVO:bvrN4CET46W(1.22):bd08/14/2026:br1.22:efr1.15:svnLENOVO:pn21Q60068BM:pvrThinkPadX9-15Gen1:rvnLENOVO:rn21Q60068BM:rvrSDK0T76576WIN:cvnLENOVO:ct10:cvrNone:skuLENOVO_MT_21Q6_BU_Think_FM_ThinkPadX9-15Gen1:pfaThinkPadX9-15Gen1: dmi.product.family: ThinkPad X9-15 Gen 1 dmi.product.name: 21Q60068BM dmi.product.sku: LENOVO_MT_21Q6_BU_Think_FM_ThinkPad X9-15 Gen 1 dmi.product.version: ThinkPad X9-15 Gen 1 dmi.sys.vendor: LENOVO To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2172563/+subscriptions