Re: [PATCH v8 3/3] PCI: Add support for PCIe WAKE# interrupt

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

On 3/17/2026 12:56 PM, Manivannan Sadhasivam wrote:
> On Fri, Mar 13, 2026 at 12:38:42PM +0530, Krishna Chaitanya Chundru wrote:
>> 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. 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 should 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, If not found, it searches in its upstream port only if upstream port
>> is Root Port. Once found, register for the wake IRQ in shared mode, as the
>> WAKE# may be shared among multiple endpoints.
>>
>> dev_pm_set_dedicated_shared_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 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.
>>
>> 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@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       | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++
>>   drivers/pci/pci.c      | 10 +++++++
>>   drivers/pci/pci.h      |  2 ++
>>   drivers/pci/probe.c    |  2 ++
>>   drivers/pci/remove.c   |  1 +
>>   include/linux/of_pci.h |  4 +++
>>   include/linux/pci.h    |  2 ++
>>   7 files changed, 95 insertions(+)
>>
>> diff --git a/drivers/pci/of.c b/drivers/pci/of.c
>> index 9f8eb5df279ed28db7a3b2fd29c65da9975c2efa..b7199d3598b31b62245716c178a5a73565efc89e 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 +588,78 @@ 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;
>> +
>> +	wake_irq = gpiod_to_irq(wake);
>> +	if (wake_irq < 0) {
>> +		pci_err(pdev, "Failed to get wake irq: %d\n", wake_irq);
>> +		return;
>> +	}
>> +
>> +	device_init_wakeup(&pdev->dev, true);
> Just set wakeup only if dev_pm_set_dedicated_shared_wake_irq() succeeds.
ack.
>> +
>> +	/*
>> +	 * dev_pm_set_dedicated_shared_wake_irq() associates a wakeup IRQ with the
>> +	 * device and requests it, but the PM core keeps it disabled by default.
>> +	 * The IRQ is enabled only when the device is allowed to wake the system
>> +	 * (during system suspend and after runtime suspend), and only if device
>> +	 * wakeup is enabled.
>> +	 *
>> +	 * When the wake IRQ fires, the wakeirq handler invokes pm_runtime_resume()
>> +	 * to bring the device back to an active power state (e.g. from D3cold to D0).
>> +	 * Once the device is active and the link is usable, the endpoint may signal
>> +	 * a PME, which is then handled by the PCI core (either via PME polling or the
>> +	 * PCIe PME service driver) to wakeup particular endpoint.
>> +	 */
>> +	ret = dev_pm_set_dedicated_shared_wake_irq(&pdev->dev, wake_irq,
>> +						   IRQ_TYPE_EDGE_FALLING);
> Isn't WAKE# a level triggered signal?
Ack. I will change IRQ_TYPE_EDGE_FALLING to IRQ_TYPE_LEVEL_LOW.
>> +	if (ret < 0) {
>> +		pci_err(pdev, "Failed to set wake IRQ: %d\n", ret);
> s/wake/WAKE#
ack.

- Krishna Chaitanya.
> - Mani
>