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Tue, 28 Apr 2026 23:42:38 -0700 (PDT) Received: from hu-krichai-hyd.qualcomm.com ([202.46.23.25]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-364a0303d59sm2021414a91.15.2026.04.28.23.42.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Apr 2026 23:42:38 -0700 (PDT) From: Krishna Chaitanya Chundru Date: Wed, 29 Apr 2026 12:12:23 +0530 Subject: [PATCH v5 1/5] PCI: host-common: Add helper to determine host bridge D3cold eligibility Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260429-d3cold-v5-1-89e9735b9df6@oss.qualcomm.com> References: <20260429-d3cold-v5-0-89e9735b9df6@oss.qualcomm.com> In-Reply-To: <20260429-d3cold-v5-0-89e9735b9df6@oss.qualcomm.com> To: Jingoo Han , Manivannan Sadhasivam , Lorenzo Pieralisi , =?utf-8?q?Krzysztof_Wilczy=C5=84ski?= , Rob Herring , Bjorn Helgaas , Will Deacon Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, jonathanh@nvidia.com, bjorn.andersson@oss.qualcomm.com, Krishna Chaitanya Chundru X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; 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This helper is intended to be used by PCI host controller drivers to decide whether they may safely put the host bridge into D3cold based on the power state and wakeup capabilities of downstream endpoints. The helper walks all devices on the all bridge buses and only allows the devices to enter D3cold if all PCIe endpoints are already in PCI_D3hot. This ensures that we do not power off the host bridge 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. So, return PME-from-D3cold capability via an output parameter so PCIe controller drivers can apply platform-specific handling to preserve wakeup functionality. Signed-off-by: Krishna Chaitanya Chundru --- drivers/pci/controller/pci-host-common.c | 71 ++++++++++++++++++++++++++++++++ drivers/pci/controller/pci-host-common.h | 2 + 2 files changed, 73 insertions(+) diff --git a/drivers/pci/controller/pci-host-common.c b/drivers/pci/controller/pci-host-common.c index d6258c1cffe5..09432d69175c 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 +109,73 @@ 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; + int type; + + /* Ignore conventional PCI devices */ + if (!pci_is_pcie(pdev)) + return 0; + + type = pci_pcie_type(pdev); + if (type != PCI_EXP_TYPE_ENDPOINT && + type != PCI_EXP_TYPE_LEG_END && + type != PCI_EXP_TYPE_RC_END) + return 0; + + 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 which is 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 b5075d4bd7eb..7eb5599b9ce4 100644 --- a/drivers/pci/controller/pci-host-common.h +++ b/drivers/pci/controller/pci-host-common.h @@ -20,4 +20,6 @@ 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 -- 2.34.1