Re: [PATCH v6 2/2] PCI: Add support for PCIe WAKE# interrupt

[Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>]

Hi Bjorn,

Can you review this patch?

- Krishna Chaitanya.
On 11/27/2025 6:15 PM, 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.
>
> 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
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.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);
> +		return;
> +	}
> +
> +	device_init_wakeup(&pdev->dev, true);
> +
> +	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);
> +		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;
> +
> +	if (!dn)
> +		return;
> +
> +	gpio = fwnode_gpiod_get_index(of_fwnode_handle(dn),
> +				      "wake", 0, GPIOD_IN | GPIOD_FLAGS_BIT_NONEXCLUSIVE, NULL);
> +	if (IS_ERR(gpio)) {
> +		/*
> +		 * To support legacy devicetree, search in root port for WAKE#
> +		 * in direct attach case.
> +		 */
> +		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);
> +
>   	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);
>   	pci_doe_sysfs_teardown(dev);
>   	pci_npem_remove(dev);
>   
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index d1fdf81fbe1e427aecbc951fa3fdf65c20450b05..cd7b5eb82a430ead2f64d903a24a5b06a1b7b17e 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -555,6 +555,8 @@ struct pci_dev {
>   	/* These methods index pci_reset_fn_methods[] */
>   	u8 reset_methods[PCI_NUM_RESET_METHODS]; /* In priority order */
>   
> +	struct gpio_desc *wake; /* Holds WAKE# gpio */
> +
>   #ifdef CONFIG_PCIE_TPH
>   	u16		tph_cap;	/* TPH capability offset */
>   	u8		tph_mode;	/* TPH mode */
>