Re: [PATCH v11] PCI: Add support for PCIe WAKE# interrupt

[Bartosz Golaszewski]

On Wed, 24 Jun 2026 13:25:49 +0200, Krishna Chaitanya Chundru
<krishna.chundru@xxxxxxxxxxxxxxxx> said:
> According to the PCI Express specification (PCIe r7.0, Section 5.3.3.2),
> two link wakeup mechanisms are defined: Beacon and WAKE#. Beacon is a
> hardware-only mechanism and is invisible to software (PCIe r7.0,
> Section 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 each component in the hierarchy could 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@xxxxxxxxxxxxxxxx/
> Link: https://github.com/devicetree-org/dt-schema/pull/170
> Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
> Acked-by: Manivannan Sadhasivam <mani@xxxxxxxxxx>
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@xxxxxxxxxxxxxxxx>
> ---

Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>