[FINAL UPDATE/DIAGNOSIS CORRECTION]: Complete Functional Fix with Partial Acoustic Calibration for iMac 18,3 (CS8409/CS42L83)
Hello, We have conducted an in-depth analysis of the sound issue (no PEQ, silent output) on the iMac 18,3 and confirm that the original diagnosis focused on UCM profiles was inaccurate. Correction: Why Software UCM Profiles Fail The root-cause problem is at the lowest level: the standard snd_hda_intel driver fails to send the proprietary HDA-Verbs sequence from Apple, which is essential to wake up and activate the Cirrus Logic CS8409/CS42L83 DSP and amplifier. Consequence: Since the hardware is not correctly initialized, it does not expose the necessary ALSA mixer controls to the system. Therefore, no UCM profile can functionally exist or solve the problem until the hardware is activated via HDA-Verbs. Functional Solution (HDA-Verbs Fix and DKMS Installer) - NOTE: PARTIAL FIX The issue is currently resolved by applying HDA-Verbs to activate the hardware and set the basic gain (GAIN fix). Implementation: We used a patched snd-hda-codec-cs8409 module (v5.0/v6.0) that applies custom Verbs (extracted from Apple Bootcamp drivers) via ALSA firmware. Status: The sound is functional and stable, all mixer controls are exposed, and audio is playing. Limitation (REASON FOR PARTIAL FIX): The fix is only partial in terms of audio quality. Although we successfully activated the DSP, the parameters used for the Parametric Equalizer (PEQ) are generic (basic GAIN/EQ). Missing Data: The optimal acoustic tuning that Apple uses (to compensate for the small iMac speaker acoustics for good bass and treble) is proprietary and is not included in the script. Result: Sound works, but does not achieve the optimal quality found in macOS until the exact PEQ data is obtained. Availability: For easy testing and deployment, I am including a functional installer script (iMac_CS8409_Installer.sh) which automates the installation of the DKMS module and HDA-Verbs configuration. Conclusion and Upstream Submission The complete bug report, diagnostic data, and functional patch have been submitted to the ALSA mailing list ([email protected]) in the required format for kernel integration. Recommendation for Ubuntu: Please follow this issue at the upstream level, as the fix requires integrating specific HDA-Verbs directly into the main kernel module (snd-hda-codec-cirrus). Once the fix is accepted, this bug should be closed as resolved in the next stable kernel release. Attachments to the bug report include (all in one ZIP): iMac_CS8409_Installer.sh (Key functional script) amixer_output_functional.txt (Proof of functionality after the fix) cs8409_verbs_config.txt (HDA-Verbs used) ucm2_status_missing_cs8409.txt (Proof that UCM profile for this HW does not exist) Thank you for your cooperation. Marek - mahav ** Attachment added: "cs8409_report.zip" https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2119402/+attachment/5915374/+files/cs8409_report.zip -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2119402 Title: )Persistent driver issues on iMac 18,3 (27", 2017) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2119402/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
