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The Candence GEM IP has a configuration parameter which determines the source of the clock used for the timestamp unit (if it is enabled), switching it between using the pclk and a dedicated input. When ptp support was added to the macb driver, a new tsu_clk was added to represent the dedicated input. While this is understandable, I think it is bug prone and that the tsu_clk should represent whatever clock is used for the timestamper and not just that specific input. >From a driver point of view, the benefit of taking the conceptual approach is avoiding misconfiguring the driver when the hardware supports ptp (and it is set as a capability in the relevant per-device structure) but no tsu_clk is provided in devicetree. At the moment, the timestamper will be registered and programmed with an increment that reflects the pclk in these cases, but will malfunction if the pclk and tsu_clk frequencies do not match. Obviously, this means the devicetree incorrectly represents the hardware, but this change in approach would make the driver more resilient without meaningfully impacting correctly described users. Out of the devices that claim MACB_CAPS_GEM_HAS_PTP the fu540, mpfs, sama5d2 and sama7g5-emac (but not sama7g5-gem) are at risk of having this problem with the in-kernel devicetrees. mpfs and sama7g5-emac have been confirmed to be incorrect, and sama5d2 is correct. It may be that the other platforms actually do use the pclk for the timestamper (either by supplying pclk to the tsu_clk input of the IP, or by having the IP block configured to use pclk instead of the tsu_clk input), but at least two are wrong, as they do not use pclk for the tsu_clk, so the driver is registering the ptp clock incorrectly. Add a warning if no tsu_clk is provided on a platform that uses the timerstamper, to encourage people to specifically provide a tsu_clk and avoid silently registering the timerstamper with the wrong clock. If the pclk is actually used, it can be provided as a tsu_clk for improved clarity in devicetrees. While this changes the meaning of the devicetree property, it is backwards compatible as there's no functional change for platforms that didn't provide a tsu_clk and the changed meaning of providing a tsu_clk in the devicetree does not impact platforms that already provided one as the decision about the tsu clock source is at IP instantiation time rather than at runtime, so there's no driver behaviour that needs to change based on the input to the IP used for the timestamping unit. Signed-off-by: Conor Dooley <conor.dooley@microchip.com> Link: https://patch.msgid.link/20260325-dust-revision-368053e82d0e@spud Signed-off-by: Jakub Kicinski <kuba@kernel.org> |
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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. 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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. 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