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dw_hdmi_qp_set_sample_rate() open-coded its own N and CTS lookup tables and search/compute helpers, but it lacked the out-of-table CTS fallback needed by strict HDMI sinks at TMDS rates not in the table. The original LG G3 OLED audio mute (linux-rockchip 070633) was caused by dw_hdmi_qp_find_cts() returning 0 at 185.625 MHz, leaving AUDPKT_ACR_CTS_OVR_EN clear and falling back to the controller's internal CTS auto-measurement, which produces incorrect timing on the wire at out-of-table rates. The shared drm_hdmi_acr_get_n_cts() helper in drivers/gpu/drm/display/drm_hdmi_helper.c already implements the correct behaviour: it has the HDMI 1.4b spec N/CTS tables, and for TMDS rates not in the table it computes CTS = (TMDS * N) / (128 * Fs) inline (the canonical HDMI spec formula). It is already used by drivers/gpu/drm/msm/hdmi/hdmi_audio.c. Convert dw_hdmi_qp_set_sample_rate() to call the helper. This removes ~200 lines of open-coded tables and search functions (dw_hdmi_qp_find_n, _compute_n, _find_cts, _audio_math_diff, _match_tmds_n_table, common_tmds_n_table[], common_tmds_cts_table[]) and fixes the strict-sink audio mute as a side effect of using the helper's complete N+CTS path. Tested on R76S (RK3576) running Linux 7.0.1, against the LG G3 OLED (the sink that originally reported the mute in linux-rockchip 070633) at four TMDS rates spanning HDMI 1.4 and HDMI 2.0: TMDS Mode Audio with v3 148.5 MHz 1080p60 8-bit plays 185.625 MHz 1080p60 10-bit plays 297 MHz 1080p100 8-bit plays 594 MHz 3840p60 8-bit plays Without this change, the LG G3 mutes audio at 185.625, 297, and 594 MHz (every rate outside dw-hdmi-qp's open-coded CTS table, which contained only 148.5 MHz and below). With this change, drm_hdmi_acr_get_n_cts() supplies the correct CTS at every rate -- table-canonical at 148.5 / 297 / 594 MHz, and computed via the HDMI 1.4b formula at 185.625 MHz. The 148.5 MHz row is a regression check confirming the in-table path is unchanged. The Kogan KALED43XU9210STA (a permissive HDMI 2.0 sink that plays audio at all rates with or without this change) was used as a no-regression control: audio plays at 594 MHz with v3 loaded. The open-coded N table in dw-hdmi-qp included optimised N values for some TMDS rates that are not in the helper's table (e.g. various non-CEA rates between 28-162 MHz). For those rates the helper's fallback returns N = 128 * Fs / 1000, which is the same value dw_hdmi_qp_compute_n() returned when no table optimisation was needed; no audio regression has been observed at the rates tested above. Reported-by: Simon Wright <simon@symple.nz> Closes: https://lore.kernel.org/linux-rockchip/ME3P282MB21960D9D68BFF520316BDFCEA83E2@ME3P282MB2196.AUSP282.PROD.OUTLOOK.COM/ Suggested-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com> Suggested-by: Jonas Karlman <jonas@kwiboo.se> Assisted-by: Claude:claude-opus-4-7 Signed-off-by: Simon Wright <simon@symple.nz> Tested-by: Igor Paunovic <royalnet026@gmail.com> # RK3588 Orange Pi 5 Plus, both HDMI controllers Tested-by: Christian Hewitt <christianshewitt@gmail.com> Reviewed-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com> Tested-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com> Signed-off-by: Heiko Stuebner <heiko@sntech.de> Link: https://patch.msgid.link/86fcf349-0a7a-4618-9001-612371b0f71b@symple.nz |
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Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. Quick Start ----------- * Report a bug: See Documentation/admin-guide/reporting-issues.rst * Get the latest kernel: https://kernel.org * Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst * Join the community: https://lore.kernel.org/ Essential Documentation ----------------------- All users should be familiar with: * Building requirements: Documentation/process/changes.rst * Code of Conduct: Documentation/process/code-of-conduct.rst * License: See COPYING Documentation can be built with make htmldocs or viewed online at: https://www.kernel.org/doc/html/latest/ Who Are You? ============ Find your role below: * New Kernel Developer: Getting started with kernel development * Academic Researcher: Studying kernel internals and architecture * Security Expert: Hardening and vulnerability analysis * Backport/Maintenance Engineer: Maintaining stable kernels * System Administrator: Configuring and troubleshooting * Maintainer: Leading subsystems and reviewing patches * Hardware Vendor: Writing drivers for new hardware * Distribution Maintainer: Packaging kernels for distros * AI Coding Assistant: LLMs and AI-powered development tools For Specific Users ================== New Kernel Developer -------------------- Welcome! Start your kernel development journey here: * Getting Started: Documentation/process/development-process.rst * Your First Patch: Documentation/process/submitting-patches.rst * Coding Style: Documentation/process/coding-style.rst * Build System: Documentation/kbuild/index.rst * Development Tools: Documentation/dev-tools/index.rst * Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst * Core APIs: Documentation/core-api/index.rst Academic Researcher ------------------- Explore the kernel's architecture and internals: * Researcher Guidelines: Documentation/process/researcher-guidelines.rst * Memory Management: Documentation/mm/index.rst * Scheduler: Documentation/scheduler/index.rst * Networking Stack: Documentation/networking/index.rst * Filesystems: Documentation/filesystems/index.rst * RCU (Read-Copy Update): Documentation/RCU/index.rst * Locking Primitives: Documentation/locking/index.rst * Power Management: Documentation/power/index.rst Security Expert --------------- Security documentation and hardening guides: * Security Documentation: Documentation/security/index.rst * LSM Development: Documentation/security/lsm-development.rst * Self Protection: Documentation/security/self-protection.rst * Reporting Vulnerabilities: Documentation/process/security-bugs.rst * CVE Procedures: Documentation/process/cve.rst * Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst * Security Features: Documentation/userspace-api/seccomp_filter.rst Backport/Maintenance Engineer ----------------------------- Maintain and stabilize kernel versions: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * Backporting Guide: Documentation/process/backporting.rst * Applying Patches: Documentation/process/applying-patches.rst * Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git for Maintainers: Documentation/maintainer/configure-git.rst System Administrator -------------------- Configure, tune, and troubleshoot Linux systems: * Admin Guide: Documentation/admin-guide/index.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst * Tracing/Debugging: Documentation/trace/index.rst * Performance Security: Documentation/admin-guide/perf-security.rst * Hardware Monitoring: Documentation/hwmon/index.rst Maintainer ---------- Lead kernel subsystems and manage contributions: * Maintainer Handbook: Documentation/maintainer/index.rst * Pull Requests: Documentation/maintainer/pull-requests.rst * Managing Patches: Documentation/maintainer/modifying-patches.rst * Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst * Development Process: Documentation/process/maintainer-handbooks.rst * Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git Configuration: Documentation/maintainer/configure-git.rst Hardware Vendor --------------- Write drivers and support new hardware: * Driver API Guide: Documentation/driver-api/index.rst * Driver Model: Documentation/driver-api/driver-model/driver.rst * Device Drivers: Documentation/driver-api/infrastructure.rst * Bus Types: Documentation/driver-api/driver-model/bus.rst * Device Tree Bindings: Documentation/devicetree/bindings/ * Power Management: Documentation/driver-api/pm/index.rst * DMA API: Documentation/core-api/dma-api.rst Distribution Maintainer ----------------------- Package and distribute the kernel: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * ABI Documentation: Documentation/ABI/README * Kernel Configuration: Documentation/kbuild/kconfig.rst * Module Signing: Documentation/admin-guide/module-signing.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst AI Coding Assistant ------------------- CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and follow the AI coding assistants documentation before contributing to the Linux kernel: * Documentation/process/coding-assistants.rst This documentation contains essential requirements about licensing, attribution, and the Developer Certificate of Origin that all AI tools must comply with. Communication and Support ========================= * Mailing Lists: https://lore.kernel.org/ * IRC: #kernelnewbies on irc.oftc.net * Bugzilla: https://bugzilla.kernel.org/ * MAINTAINERS file: Lists subsystem maintainers and mailing lists * Email Clients: Documentation/process/email-clients.rst