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Some platforms require selectively disabling specific ASPM states on a
given PCIe link to avoid link instability or functional failures caused by
board-level connectivity constraints such as PCB routing, connectors,
slots, or external cabling.
Devicetree supports disabling ASPM L0s, L1, and L1 PM Substates via the
'aspm-no-l0s', 'aspm-no-l1' [1], and 'aspm-no-l1ss' [2] properties.
However, the ASPM driver does not currently honor these properties when
initializing the default link state.
When firmware enables L1 PM Substates before the kernel takes over,
masking aspm_support alone is insufficient to disable them in hardware.
pcie_config_aspm_link() guards L1SS configuration behind a check on
aspm_capable, which is derived from aspm_support. Once aspm_support is
masked, pcie_config_aspm_l1ss() is never called, leaving
firmware-enabled L1SS substates active in hardware.
Fix this by introducing pcie_link_has_aspm_override() to check for DT
override properties on either endpoint of the link. In
pcie_aspm_override_default_link_state(), use it to:
- Mask aspm_support, aspm_default, and aspm_enabled for any disabled
state, so software's view of the link stays in sync with what is
actually programmed in hardware. Leaving aspm_enabled stale would make
pcie_aspm_enabled() and the aspm sysfs attributes report a state as
active even after it has been masked, and could cause
pcie_config_aspm_link()'s "already in requested state" check to skip
reprogramming hardware to match.
- Explicitly call pcie_config_aspm_l1ss(link, 0) before masking
aspm_support when firmware has L1SS active and DT requests disabling L1
or L1SS, since pcie_config_aspm_link() will no longer do so once
aspm_capable is derived from the masked aspm_support.
Move the aspm_default initialization and
pcie_aspm_override_default_link_state() call in pcie_aspm_cap_init() to
before the "Restore L0s/L1" block. pcie_aspm_cap_init() disables L1 in
hardware prior to aspm_l1ss_init() and re-enables it only in the restore
block. Calling pcie_config_aspm_l1ss() while L1 is already disabled
satisfies its precondition ("Caller must disable L1 first"), whereas the
previous placement after the restore violated it.
Since the restore block writes back the parent_lnkctl/child_lnkctl snapshot
taken from hardware before the DT override ran, mask the L0s and L1 enable
bits out of that snapshot for any state the override has just disabled in
aspm_support. Otherwise the restore step would unconditionally reprogram
the link back to firmware's original L0s/L1 configuration, defeating the
Devicetree override it is meant to enforce.
Move pcie_config_aspm_l1ss() earlier in the file so it can be called
from pcie_aspm_override_default_link_state().
Link [1]: https://github.com/devicetree-org/dt-schema/pull/188
Link [2]: https://github.com/devicetree-org/dt-schema/pull/190
Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://patch.msgid.link/20260727-aspm-v6-3-2ebb3ee7ef71@oss.qualcomm.com
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| README | ||
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