From: Krishna Chaitanya Chundru Date: Wed, 29 Apr 2026 06:42:23 +0000 (+0530) Subject: PCI: host-common: Add pci_host_common_d3cold_possible() helper X-Git-Tag: v7.2-rc1~40^2~13^2~10 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1d2a29ccd3a17d8e3ab8c3a4821b96d19c799b12;p=thirdparty%2Fkernel%2Flinux.git PCI: host-common: Add pci_host_common_d3cold_possible() helper Add a common helper, pci_host_common_d3cold_possible(), to determine whether PCIe devices under host bridge can safely transition to D3cold. This helper is intended to be used by PCI host controller drivers to decide whether they can safely put the endpoint devices into D3cold based on their power state and wakeup capabilities. Once the devices are transitioned into D3cold, the host controller can be safely powered off. The helper walks all devices on the all downstream buses and only allows the devices to enter D3cold if all PCIe endpoints are already in PCI_D3hot. This ensures that the host controller driver does not broadcast PME_Turn_Off or power down the controller while any active endpoint still requires the link to remain powered. For devices that may wake the system, the helper additionally requires that the device supports PME wake from D3cold (via WAKE#). Devices that do not have wakeup enabled are not restricted by this check and do not block the devices under host bridge from entering D3cold. Devices without a bound driver and with PCI not enabled via sysfs are treated as inactive and therefore do not prevent the devices under host bridge from entering D3cold. This allows controllers to power down more aggressively when there are no actively managed endpoints. Some devices (e.g. M.2 without auxiliary power) lose PME detection when main power is removed. Even if such devices advertise PME-from-D3cold capability, entering D3cold may break wakeup. Return PME-from-D3cold capability via 'pme_capable' parameter so PCIe controller drivers can apply platform-specific handling to preserve wakeup functionality. Signed-off-by: Krishna Chaitanya Chundru [mani: commit log and removed the device checks for d3cold] Signed-off-by: Manivannan Sadhasivam Signed-off-by: Bjorn Helgaas Link: https://patch.msgid.link/20260429-d3cold-v5-1-89e9735b9df6@oss.qualcomm.com --- diff --git a/drivers/pci/controller/pci-host-common.c b/drivers/pci/controller/pci-host-common.c index d6258c1cffe5e..2e785449d02cb 100644 --- a/drivers/pci/controller/pci-host-common.c +++ b/drivers/pci/controller/pci-host-common.c @@ -17,6 +17,9 @@ #include "pci-host-common.h" +#define PCI_HOST_D3COLD_ALLOWED BIT(0) +#define PCI_HOST_PME_D3COLD_CAPABLE BIT(1) + static void gen_pci_unmap_cfg(void *ptr) { pci_ecam_free((struct pci_config_window *)ptr); @@ -106,5 +109,64 @@ void pci_host_common_remove(struct platform_device *pdev) } EXPORT_SYMBOL_GPL(pci_host_common_remove); +static int __pci_host_common_d3cold_possible(struct pci_dev *pdev, + void *userdata) +{ + u32 *flags = userdata; + + if (!pdev->dev.driver && !pci_is_enabled(pdev)) + return 0; + + if (pdev->current_state != PCI_D3hot) + goto exit; + + if (device_may_wakeup(&pdev->dev)) { + if (!pci_pme_capable(pdev, PCI_D3cold)) + goto exit; + else + *flags |= PCI_HOST_PME_D3COLD_CAPABLE; + } + + return 0; + +exit: + *flags &= ~PCI_HOST_D3COLD_ALLOWED; + + return -EOPNOTSUPP; +} + +/** + * pci_host_common_d3cold_possible - Determine whether the host bridge can + * transition the devices into D3cold. + * + * @bridge: PCI host bridge to check + * @pme_capable: Pointer to update if there is any device capable of generating + * PME from D3cold. + * + * Walk downstream PCIe endpoint devices and determine whether the host bridge + * is permitted to transition the devices into D3cold. + * + * Devices under host bridge can enter D3cold only if all active PCIe + * endpoints are in PCI_D3hot and any wakeup-enabled endpoint is capable of + * generating PME from D3cold. Inactive endpoints are ignored. + * + * The @pme_capable output allows PCIe controller drivers to apply + * platform-specific handling to preserve wakeup functionality. + * + * Return: %true if the host bridge may enter D3cold, otherwise %false. + */ +bool pci_host_common_d3cold_possible(struct pci_host_bridge *bridge, + bool *pme_capable) +{ + u32 flags = PCI_HOST_D3COLD_ALLOWED; + + pci_walk_bus(bridge->bus, __pci_host_common_d3cold_possible, &flags); + + *pme_capable = !!(flags & PCI_HOST_PME_D3COLD_CAPABLE); + + return !!(flags & PCI_HOST_D3COLD_ALLOWED); +} +EXPORT_SYMBOL_GPL(pci_host_common_d3cold_possible); + MODULE_DESCRIPTION("Common library for PCI host controller drivers"); MODULE_LICENSE("GPL v2"); diff --git a/drivers/pci/controller/pci-host-common.h b/drivers/pci/controller/pci-host-common.h index b5075d4bd7eb3..1649858782659 100644 --- a/drivers/pci/controller/pci-host-common.h +++ b/drivers/pci/controller/pci-host-common.h @@ -20,4 +20,7 @@ void pci_host_common_remove(struct platform_device *pdev); struct pci_config_window *pci_host_common_ecam_create(struct device *dev, struct pci_host_bridge *bridge, const struct pci_ecam_ops *ops); + +bool pci_host_common_d3cold_possible(struct pci_host_bridge *bridge, + bool *pme_capable); #endif