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Message-ID: <ip6k4kjyu5lrnafqyrnq54dw6lqixaqx7wckwn3ttxr7hpu4ob@77l52tthlfnp>
Date: Fri, 16 Jan 2026 17:26:33 +0530
From: Manivannan Sadhasivam <mani@...nel.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>,
Linus Walleij <linus.walleij@...aro.org>, 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 v6 2/2] PCI: Add support for PCIe WAKE# interrupt
On Thu, Nov 27, 2025 at 06:15:43PM +0530, Krishna Chaitanya Chundru 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.
Use imperative tone.
>
> According to the PCIe specification, multiple WAKE# signals can exist in
> a system.
Add '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, WAKE# can
Add spec revision.
> 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
'endpoint'
> endpoints share a single WAKE# line, then WAKE# should be defined in the
> each node.
>
'.., then each endpoint node should describe the same WAKE# signal or a single
WAKE# in the Root Port 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.
>
This is not a legacy way. If there is a single WAKE#, then DTS may still
describe it only in the Root Port node.
> In pci_device_add(), PCI framework will search for the WAKE# in its node,
s/its/device
> 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
s/root port/Root Port
Again, drop 'legacy binding'.
> in shared mode, as the WAKE# may be shared among multiple endpoints.
>
> When the IRQ is asserted, the handle_threaded_wake_irq() handler triggers
handle_threaded_wake_irq() is not part of this patch. So maybe say,
'When a device asserts WAKE#, PM core will wakeup the system, resume the device
and its parent(s) in the hierarchy, which will cause the restoration of power
and refclk to the device.'
> 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
> Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
> ---
> 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 ++
> 5 files changed, 69 insertions(+)
>
> diff --git a/drivers/pci/of.c b/drivers/pci/of.c
> index 3579265f119845637e163d9051437c89662762f8..fc33405a7b1f001e171277434663cc9dfe57c69b 100644
> --- a/drivers/pci/of.c
> +++ b/drivers/pci/of.c
> @@ -7,6 +7,7 @@
> #define pr_fmt(fmt) "PCI: OF: " fmt
>
> #include <linux/cleanup.h>
> +#include <linux/gpio/consumer.h>
> #include <linux/irqdomain.h>
> #include <linux/kernel.h>
> #include <linux/pci.h>
> @@ -15,6 +16,7 @@
> #include <linux/of_address.h>
> #include <linux/of_pci.h>
> #include <linux/platform_device.h>
> +#include <linux/pm_wakeirq.h>
> #include "pci.h"
>
> #ifdef CONFIG_PCI
> @@ -586,6 +588,62 @@ int of_irq_parse_and_map_pci(const struct pci_dev *dev, u8 slot, u8 pin)
> return irq_create_of_mapping(&oirq);
> }
> EXPORT_SYMBOL_GPL(of_irq_parse_and_map_pci);
> +
> +static void pci_configure_wake_irq(struct pci_dev *pdev, struct gpio_desc *wake)
> +{
> + int ret, wake_irq;
> +
> + if (!wake)
> + return;
> +
> + wake_irq = gpiod_to_irq(wake);
> + if (wake_irq < 0) {
> + dev_err(&pdev->dev, "Failed to get wake irq: %d\n", wake_irq);
Why not pci_err()?
> + return;
> + }
> +
> + device_init_wakeup(&pdev->dev, true);
I don't think we should enable wakeup by default for all devices, but only
conditionally in platform_pci_set_wakeup().
> +
> + ret = dev_pm_set_dedicated_shared_wake_irq(&pdev->dev, wake_irq,
> + IRQ_TYPE_EDGE_FALLING);
> + if (ret < 0) {
> + dev_err(&pdev->dev, "Failed to set wake IRQ: %d\n", ret);
pci_err()?
> + device_init_wakeup(&pdev->dev, false);
> + }
> +}
> +
> +void pci_configure_of_wake_gpio(struct pci_dev *dev)
> +{
> + struct device_node *dn = pci_device_to_OF_node(dev);
> + struct gpio_desc *gpio;
> + struct pci_dev *root;
s/root/upstream
> +
> + if (!dn)
> + return;
> +
> + gpio = fwnode_gpiod_get_index(of_fwnode_handle(dn),
> + "wake", 0, GPIOD_IN | GPIOD_FLAGS_BIT_NONEXCLUSIVE, NULL);
You can add a new fwnode_gpiod_get() API that wraps
fwnode_gpiod_get_index(..0..), similar to devm_fwnode_gpiod_get().
> + if (IS_ERR(gpio)) {
> + /*
> + * To support legacy devicetree, search in root port for WAKE#
> + * in direct attach case.
"In case the entire topology shares a single WAKE# signal, look for it in the
upstream bridge node. But if it is not Root Port, then skip it."
> + */
> + root = pci_upstream_bridge(dev);
> + if (pci_is_root_bus(root->bus))
> + pci_configure_wake_irq(dev, root->wake);
> + } else {
> + dev->wake = gpio;
> + pci_configure_wake_irq(dev, gpio);
> + }
> +}
> +
> +void pci_remove_of_wake_gpio(struct pci_dev *dev)
> +{
> + dev_pm_clear_wake_irq(&dev->dev);
> + device_init_wakeup(&dev->dev, false);
> + gpiod_put(dev->wake);
> + dev->wake = NULL;
> +}
> #endif /* CONFIG_OF_IRQ */
>
> static int pci_parse_request_of_pci_ranges(struct device *dev,
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 4492b809094b5794bd94dfbc20102cb208c3fa2f..05cb240ecdb59f9833ca6dae2357fdbd012195d6 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -1056,6 +1056,9 @@ void pci_release_of_node(struct pci_dev *dev);
> void pci_set_bus_of_node(struct pci_bus *bus);
> void pci_release_bus_of_node(struct pci_bus *bus);
>
> +void pci_configure_of_wake_gpio(struct pci_dev *dev);
> +void pci_remove_of_wake_gpio(struct pci_dev *dev);
> +
> int devm_of_pci_bridge_init(struct device *dev, struct pci_host_bridge *bridge);
> bool of_pci_supply_present(struct device_node *np);
> int of_pci_get_equalization_presets(struct device *dev,
> @@ -1101,6 +1104,9 @@ static inline int devm_of_pci_bridge_init(struct device *dev, struct pci_host_br
> return 0;
> }
>
> +static inline void pci_configure_of_wake_gpio(struct pci_dev *dev) { }
> +static inline void pci_remove_of_wake_gpio(struct pci_dev *dev) { }
> +
> static inline bool of_pci_supply_present(struct device_node *np)
> {
> return false;
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 0ce98e18b5a876afe72af35a9f4a44d598e8d500..f9b879c8e3f72a9845f60577335019aa2002dc23 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2762,6 +2762,8 @@ void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
> ret = device_add(&dev->dev);
> WARN_ON(ret < 0);
>
> + pci_configure_of_wake_gpio(dev);
This should be wrapped inside a new platform_pci_configure_wake() API, similar
to other platform APIs.
> +
> pci_npem_create(dev);
>
> pci_doe_sysfs_init(dev);
> diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
> index ce5c25adef5518e5aec30c41de37ea66d682f3b0..26e9c1df51c76344a1d7f5cc7edd433780e73474 100644
> --- a/drivers/pci/remove.c
> +++ b/drivers/pci/remove.c
> @@ -54,6 +54,7 @@ static void pci_destroy_dev(struct pci_dev *dev)
> if (pci_dev_test_and_set_removed(dev))
> return;
>
> + pci_remove_of_wake_gpio(dev);
Same as above, wrap it inside platform_pci_remove_wake() API.
- Mani
--
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