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On Layerscape, some Lynx SerDes consumers go through the PHY framework (we call these 'managed' for the sake of this discussion; they are some Ethernet lanes), and some consumers don't go through the PHY framework (we call these 'unmanaged'; they are some unconverted Ethernet lanes, plus all SATA and PCIe controllers). A lane is initially unmanaged, and becomes managed when phy_init() is called on it. Similarly, it becomes unmanaged again when phy_exit() is called. Managed lanes are supposed to have power management through phy_power_on() and phy_power_off(). The lynx-28g SerDes driver, when it probes, probes on all lanes, but needs to be careful to keep the unmanaged lanes powered on, because those might be in use by consumers unaware that they need to call phy_init() and phy_power_on(). This also applies after phy_exit() is called - no guarantee is made about how the port may be used afterwards - may be DPDK, may be something else which is unaware of the PHY framework. Given this state table: State | Consumer calls phy_exit()? | Provider implements phy_exit()? -------+----------------------------+-------------------------------- (a) | no | no (b) | no | yes (c) | yes | no (d) | yes | yes we are currently in state (a). This has the problem that when the consumer fails to probe with -EPROBE_DEFER or is otherwise unbound, the phy->init_count remains elevated and the lane never returns to the unmanaged state (temporarily or not) as it should. Furthermore, the second and subsequent phy_init() consumer calls are never passed on to the provider driver. We solve the above problem by implementing phy_exit() in the consumer, and that moves us to state (c). But this creates the problem that a balanced set of phy_init() and phy_exit() calls from the consumer will effectively result in multiple lynx_28g_init() calls as seen by the SerDes and nothing else - as the optional phy_ops :: exit() is not implemented. But that actually doesn't work - the 28G Lynx SerDes can't power down a lane which is already powered down; that call sequence would time out and fail. So actually we want to be in state (d), where both the provider and the consumer implement phy_exit(). But we can only do that safely through intermediary state (b), where the provider implements it first. This effectively behaves just like (a), except it offers a safe migration path for the consumer to call phy_exit() as mandated by the Generic PHY API. Extra development notes: ignoring the lynx_28g_power_on() error in lynx_28g_exit() is a deliberate decision. The consumer can't deal with a teardown path that is not error-free. Ignoring the error is not silent: lynx_28g_power_on() -> lynx_28g_lane_reset() will print on failure. Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> Link: https://patch.msgid.link/20260321011451.1557091-4-vladimir.oltean@nxp.com Signed-off-by: Vinod Koul <vkoul@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. 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. 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