[Bug 2165857] Re: snd_ctxfi: CA20K2 SB1270 S/PDIF IEC61937 passthrough fails with multiple=2 due to unhandled DAIO conf 0x9

** 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/2165857 Title: snd_ctxfi: CA20K2 SB1270 S/PDIF IEC61937 passthrough fails with multiple=2 due to unhandled DAIO conf 0x9 Status in linux package in Ubuntu: New Bug description: IEC61937 S/PDIF passthrough fails on a Creative Sound Blaster X-Fi Titanium HD SB1270 (CA20K2) using the snd_ctxfi driver when the driver operates with: reference_rate=48000 multiple=2 The same hardware and S/PDIF output work when using multiple=1. Affected Ubuntu kernel: linux-image-7.0.0-30-generic 7.0.0-30.30 The Apport report confirms that this kernel package has origin: Ubuntu. S/PDIF PCM device used for testing: hw:0,4 ## Steps to reproduce 1. Load the stock snd_ctxfi driver with: reference_rate=48000 multiple=2 2. Send an IEC61937 AC3/DTS encoded stream through the X-Fi S/PDIF PCM device hw:0,4. 3. Encoded S/PDIF passthrough fails. 4. Change the driver configuration to: reference_rate=48000 multiple=1 5. Repeat exactly the same IEC61937 test. Result: passthrough works. ## Expected result IEC61937 AC3/DTS passthrough should work with: reference_rate=48000 multiple=2 ## Actual result With the stock snd_ctxfi driver: multiple=2 -> FAIL multiple=1 -> PASS ## Root cause analysis The problem was isolated to the CA20K2 DAIO transmitter configuration. In: sound/pci/ctxfi/ctdaio.c the configuration is generated as: conf = (desc->msr & 0x7) | (desc->passthru << 3); For the failing passthrough configuration, this produces: conf == 0x9 The CA20K2 implementation in: sound/pci/ctxfi/cthw20k2.c uses: switch (conf & 0xf) to configure ATXCTL_NUC. The existing switch handles cases 1, 2, 4 and 8, but does not handle case 9. A minimal test modification was made so that configuration 9 is handled together with configuration 1: case 1: case 9: set_field(&ctl->txctl[idx], ATXCTL_NUC, 0); break; A replacement snd-ctxfi.ko was rebuilt from the source corresponding to the running Ubuntu kernel. No unrelated driver logic was changed. The rebuilt module has matching vermagic: 7.0.0-30-generic The patched driver was then tested again using the original configuration: reference_rate=48000 multiple=2 Results: IEC61937 AC3 passthrough: PASS IEC61937 DTS passthrough: PASS 5.1 decoding/output: PASS Additional regression tests of the audio driver passed. This demonstrates that multiple=1 is only a workaround. The CA20K2 hardware is capable of correct IEC61937 passthrough with multiple=2 once configuration 0x9 is explicitly handled. The same missing case 9 is also present in the current upstream Linux snd_ctxfi CA20K2 implementation, so this does not appear to be an Ubuntu-specific source modification. I can provide the exact minimal source diff/patch and additional test details if required. ProblemType: Bug DistroRelease: AnduinOS 2.0.2 Package: linux-image-7.0.0-30-generic 7.0.0-30.30 [origin: Ubuntu] ProcVersionSignature: Ubuntu 7.0.0-30.30-generic 7.0.12 Uname: Linux 7.0.0-30-generic x86_64 ApportVersion: 2.34.1-0ubuntu0.1 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: zorgan 3141 F.... wireplumber /dev/snd/controlC1: zorgan 3141 F.... wireplumber /dev/snd/seq: zorgan 3133 F.... pipewire CasperMD5CheckResult: unknown CurrentDesktop: GNOME Date: Sun Aug 30 21:38:19 2026 MachineType: Gigabyte Technology Co., Ltd. Z590 D ProcFB: 0 nvidia-drmdrmfb ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-7.0.0-30-generic root=UUID=8506df91-3e89-4e62-8c8b-165299db5989 ro quiet splash preempt=full PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No PulseAudio daemon running, or not running as session daemon. RfKill: Error: [Errno 2] No such file or directory: 'rfkill' SourcePackage: linux UpgradeStatus: No upgrade log present (probably fresh install) WifiSyslog: dmi.bios.date: 06/10/2025 dmi.bios.release: 5.19 dmi.bios.vendor: American Megatrends International, LLC. dmi.bios.version: F11b dmi.board.asset.tag: Default string dmi.board.name: Z590 D dmi.board.vendor: Gigabyte Technology Co., Ltd. dmi.board.version: Default string dmi.chassis.asset.tag: Default string dmi.chassis.type: 3 dmi.chassis.vendor: Default string dmi.chassis.version: Default string dmi.modalias: dmi:bvnAmericanMegatrendsInternational,LLC.:bvrF11b:bd06/10/2025:br5.19:svnGigabyteTechnologyCo.,Ltd.:pnZ590D:pvrDefaultstring:rvnGigabyteTechnologyCo.,Ltd.:rnZ590D:rvrDefaultstring:cvnDefaultstring:ct3:cvrDefaultstring:skuDefaultstring:pfaZ590MB: dmi.product.family: Z590 MB dmi.product.name: Z590 D dmi.product.sku: Default string dmi.product.version: Default string dmi.sys.vendor: Gigabyte Technology Co., Ltd. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2165857/+subscriptions