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According to PCIe r7.0, sec 5.3.3.2, two link wakeup mechanisms are defined: Beacon and WAKE#. Beacon is a hardware-only mechanism and is invisible to software (sec 4.2.7.8.1). This change adds support for the WAKE# mechanism in the PCI core. According to the PCIe specification, multiple WAKE# signals can exist in a system or several components in the hierarchy may share a single WAKE# signal. In configurations involving a PCIe switch, each downstream port (DSP) of the switch may be connected to a separate WAKE# line, allowing each endpoint to signal WAKE# independently. From figure 5.4 in sec 5.3.3.2, WAKE# can also be terminated at the switch itself. Such topologies are typically not described in Device Tree, therefore it is out of scope for this series. To support this, the WAKE# should be described in the device tree node of the endpoint/bridge. If all endpoints share a single WAKE# line, then each endpoint node shall describe the same WAKE# signal or a single WAKE# in the Root Port node. In pci_device_add(), PCI framework will search for the WAKE# in device node. Once found, register for the wake IRQ through dev_pm_set_dedicated_wake_irq() associates a wakeup IRQ with a device and requests it, but the PM core keeps the IRQ disabled by default. The IRQ is enabled by the PM core, only when the device is permitted to wake the system, i.e. during system suspend and after runtime suspend, and only when device wakeup is enabled. If the same WAKE# GPIO is described in multiple device tree nodes, only the first device that successfully registers the wake IRQ will succeed, while subsequent registrations may fail. This limitation does not affect functional correctness, since WAKE# is only used to bring the link to D0, and endpoint-specific wakeup handling is resolved later through PME detection (PME_EN is set in suspend path by PCI core by default). When the wake IRQ fires, the wakeirq handler invokes pm_runtime_resume() to bring the device back to an active power state, such as transitioning from D3cold to D0. Once the device is active and the link is usable, the endpoint may generate a PME, which is then handled by the PCI core through PME polling or the PCIe PME service driver to complete the wakeup of the endpoint. WAKE# is added in dts schema and merged based on below links. Link: https://lore.kernel.org/all/20250515090517.3506772-1-krishna.chundru@oss.qualcomm.com/ Link: https://github.com/devicetree-org/dt-schema/pull/170 Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com> Acked-by: Manivannan Sadhasivam <mani@kernel.org> Link: https://patch.msgid.link/20260707-wakeirq_support-v12-1-b4453f5bcc97@oss.qualcomm.com
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! 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