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

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

A Gentle remainder.

- Krishna Chaitanya.

On 12/11/2025 6:12 AM, Krishna Chaitanya Chundru wrote:
> 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 */
>>
>