linux-kernel - [PATCH v5 0/2] PCI: Add support for PCIe WAKE# interrupt

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Message-Id: <20251107-wakeirq_support-v5-0-464e17f2c20c@oss.qualcomm.com>
Date: Fri, 07 Nov 2025 14:52:23 +0530
From: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>,
        Pavel Machek <pavel@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Danilo Krummrich <dakr@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>
Cc: linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-gpio@...r.kernel.org,
        quic_vbadigan@...cinc.com, quic_mrana@...cinc.com, sherry.sun@....com,
        Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
Subject: [PATCH v5 0/2] PCI: Add support for PCIe WAKE# interrupt

PCIe WAKE# interrupt is needed for bringing back PCIe device state from
D3cold to D0.

This is pending from long time, there was two attempts done previously to
add WAKE# support[1], [2]. Those series tried to add support for legacy
interrupts along with WAKE#. Legacy interrupts are already available in
the latest kernel and we can ignore them. For the wake IRQ the series is
trying to use interrupts property define in the device tree.

This series is using gpio property instead of interrupts, from
gpio desc driver will allocate the dedicate IRQ.

According to the PCIe specification 6, sec 5.3.3.2, there are two defined
wakeup mechanisms: Beacon and WAKE# for the Link wakeup mechanisms to
provide a means of signaling the platform to re-establish power and
reference clocks to the components within its domain. Beacon is a hardware
mechanism invisible to software (PCIe r7.0, sec 4.2.7.8.1). Adding WAKE#
support in PCI framework.

According to the PCIe specification, multiple WAKE# signals can exist in
a system. 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. To support this, the WAKE#
should be described in the device tree node of the endpint/bridge. If all
endpoints share a single WAKE# line, then WAKE# should be defined in the
each node.

To support legacy devicetree in direct attach case, driver will search
in root port node for WAKE# if the driver doesn't find in the endpoint
node.

In pci_device_add(), PCI framework will search for the WAKE# in its node,
If not found, it searches in its upstream port only if upstream port is
root port to support legacy bindings. Once found, register for the wake IRQ
in shared mode, as the WAKE# may be shared among multiple endpoints.

When the IRQ is asserted, the handle_threaded_wake_irq() handler triggers
a pm_runtime_resume(). The PM framework ensures that the parent device is
resumed before the child i.e controller driver which can bring back device
state to D0.

WAKE# is added in dts schema and merged based on this patch.
https://lore.kernel.org/all/20250515090517.3506772-1-krishna.chundru@oss.qualcomm.com/

[1]: https://lore.kernel.org/all/b2b91240-95fe-145d-502c-d52225497a34@nvidia.com/T/
[2]: https://lore.kernel.org/all/20171226023646.17722-1-jeffy.chen@rock-chips.com/

Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
---
Changes in v5:
- Enable WAKE# irq only when there is wake -gpios defined in its device
  tree node (Bjorn).
- For legacy bindings for direct atach check in root port if we haven't
  find the wake in the endpoint node.
- Instead of hooking wake in driver bound case, do it in the framework
  irrespective of the driver state (Bjorn).
- Link to v4: https://lore.kernel.org/r/20250801-wake_irq_support-v4-0-6b6639013a1a@oss.qualcomm.com

Changes in v4:
- Move wake from portdrv to core framework to endpoint (Bjorn).
- Added support for multiple WAKE# case (Bjorn). But traverse from
  endpoint upstream port to root port till you get WAKE#. And use
  IRQF_SHARED flag for requesting interrupts.
- Link to v3: https://lore.kernel.org/r/20250605-wake_irq_support-v3-0-7ba56dc909a5@oss.qualcomm.com

Changes in v3:
- Update the commit messages, function names etc as suggested by Mani.
- return wake_irq if returns error (Neil).
- Link to v2: https://lore.kernel.org/r/20250419-wake_irq_support-v2-0-06baed9a87a1@oss.qualcomm.com

Changes in v2:
- Move the wake irq teardown after pcie_port_device_remove
  and move of_pci_setup_wake_irq before pcie_link_rcec (Lukas)
- teardown wake irq in shutdown also.
- Link to v1: https://lore.kernel.org/r/20250401-wake_irq_support-v1-0-d2e22f4a0efd@oss.qualcomm.com

---
Krishna Chaitanya Chundru (2):
      PM: sleep: wakeirq: Add support for custom IRQ flags in dedicated wake IRQ setup
      PCI: Add support for PCIe WAKE# interrupt

 drivers/base/power/wakeirq.c | 43 ++++++++++++++++++++++++++++----
 drivers/pci/of.c             | 58 ++++++++++++++++++++++++++++++++++++++++++++
 drivers/pci/pci.h            |  6 +++++
 drivers/pci/probe.c          |  2 ++
 drivers/pci/remove.c         |  1 +
 include/linux/pci.h          |  2 ++
 include/linux/pm_wakeirq.h   |  6 +++++
 7 files changed, 113 insertions(+), 5 deletions(-)
---
base-commit: f04a8f2f1f04a77e65d96f5ee146957522002900
change-id: 20251104-wakeirq_support-f54c4baa18c5

Best regards,
-- 
Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>