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

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Message-ID: <CACRpkdY9HsnG=xo=swnMcVha+unmvmxR6e6Ynsj09srM_tPmWA@mail.gmail.com>
Date: Tue, 11 Nov 2025 00:57:50 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
Cc: "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>, Bartosz Golaszewski <brgl@...ev.pl>, 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
Subject: Re: [PATCH v5 2/2] PCI: Add support for PCIe WAKE# interrupt

On Fri, Nov 7, 2025 at 10:22 AM Krishna Chaitanya Chundru
<krishna.chundru@....qualcomm.com> wrote:

> 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. From figure 5.4, WAKE# can
> also be terminated at the switch itself. 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 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@....qualcomm.com>

The GPIO parts look all right to me, a bit complex since we can't use
devm_* stuff here, but that happens.
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij