From: Manivannan Sadhasivam Date: Fri, 2 Jan 2026 15:34:47 +0000 (+0530) Subject: PCI: Enable ACS after configuring IOMMU for OF platforms X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c41e2fb67e26b04d919257875fa954aa5f6e392e;p=thirdparty%2Fkernel%2Flinux.git PCI: Enable ACS after configuring IOMMU for OF platforms Platform, ACPI, or IOMMU drivers call pci_request_acs(), which sets 'pci_acs_enable' to request that ACS be enabled for any devices enumerated in the future. OF platforms called pci_enable_acs() for the first device before of_iommu_configure() called pci_request_acs(), so ACS was never enabled for that device (typically a Root Port). Call pci_enable_acs() later, from pci_dma_configure(), after of_dma_configure() has had a chance to call pci_request_acs(). Here's the call path, showing the move of pci_enable_acs() from pci_acs_init() to pci_dma_configure(), where it always happens after pci_request_acs(): pci_device_add pci_init_capabilities pci_acs_init - pci_enable_acs - if (pci_acs_enable) <-- previous test - ... device_add bus_notify(BUS_NOTIFY_ADD_DEVICE) iommu_bus_notifier iommu_probe_device iommu_init_device dev->bus->dma_configure pci_dma_configure # pci_bus_type.dma_configure of_dma_configure of_iommu_configure pci_request_acs pci_acs_enable = 1 <-- set + pci_enable_acs + if (pci_acs_enable) <-- new test + ... bus_probe_device device_initial_probe ... really_probe dev->bus->dma_configure pci_dma_configure # pci_bus_type.dma_configure ... pci_enable_acs Note that we will now call pci_enable_acs() twice for every device, first from the iommu_probe_device() path and again from the really_probe() path. Presumably that's not an issue since we also call dev->bus->dma_configure() twice. For the ACPI platforms, pci_request_acs() is called during ACPI initialization time itself, independent of the IOMMU framework. Signed-off-by: Manivannan Sadhasivam [bhelgaas: commit log] Signed-off-by: Bjorn Helgaas Tested-by: Marek Szyprowski Tested-by: Naresh Kamboju Link: https://patch.msgid.link/20260102-pci_acs-v3-1-72280b94d288@oss.qualcomm.com --- diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c index 7c2d9d596258..301a9418e38e 100644 --- a/drivers/pci/pci-driver.c +++ b/drivers/pci/pci-driver.c @@ -1650,6 +1650,14 @@ static int pci_dma_configure(struct device *dev) ret = acpi_dma_configure(dev, acpi_get_dma_attr(adev)); } + /* + * Attempt to enable ACS regardless of capability because some Root + * Ports (e.g. those quirked with *_intel_pch_acs_*) do not have + * the standard ACS capability but still support ACS via those + * quirks. + */ + pci_enable_acs(to_pci_dev(dev)); + pci_put_host_bridge_device(bridge); /* @drv may not be valid when we're called from the IOMMU layer */ diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 5c109f62eb4a..647c3c4eb482 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -1016,7 +1016,7 @@ static void pci_std_enable_acs(struct pci_dev *dev, struct pci_acs *caps) * pci_enable_acs - enable ACS if hardware support it * @dev: the PCI device */ -static void pci_enable_acs(struct pci_dev *dev) +void pci_enable_acs(struct pci_dev *dev) { struct pci_acs caps; bool enable_acs = false; @@ -3649,14 +3649,6 @@ bool pci_acs_path_enabled(struct pci_dev *start, void pci_acs_init(struct pci_dev *dev) { dev->acs_cap = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ACS); - - /* - * Attempt to enable ACS regardless of capability because some Root - * Ports (e.g. those quirked with *_intel_pch_acs_*) do not have - * the standard ACS capability but still support ACS via those - * quirks. - */ - pci_enable_acs(dev); } /** diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index 0e67014aa001..4592ede0ebcc 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -939,6 +939,7 @@ static inline resource_size_t pci_resource_alignment(struct pci_dev *dev, } void pci_acs_init(struct pci_dev *dev); +void pci_enable_acs(struct pci_dev *dev); #ifdef CONFIG_PCI_QUIRKS int pci_dev_specific_acs_enabled(struct pci_dev *dev, u16 acs_flags); int pci_dev_specific_enable_acs(struct pci_dev *dev);