iommu/of: Support ats-supported device-tree property

Device-tree declares whether a PCI root-complex supports ATS by setting
the "ats-supported" property. Copy this flag into device fwspec to let
IOMMU drivers quickly check if they can enable ATS for a device.
Tested-by: Ketan Patil <ketanp@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Link: https://lore.kernel.org/r/20240607105415.2501934-4-jean-philippe@linaro.orgSigned-off-by: Will Deacon <will@kernel.org>

drivers/iommu/of_iommu.c

@@ -105,6 +105,14 @@ static int of_iommu_configure_device(struct device_node *master_np,
 		      of_iommu_configure_dev(master_np, dev);
 }
 
+static void of_pci_check_device_ats(struct device *dev, struct device_node *np)
+{
+	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
+
+	if (fwspec && of_property_read_bool(np, "ats-supported"))
+		fwspec->flags |= IOMMU_FWSPEC_PCI_RC_ATS;
+}
+
 /*
  * Returns:
  *  0 on success, an iommu was configured
@@ -147,6 +155,7 @@ int of_iommu_configure(struct device *dev, struct device_node *master_np,
 		pci_request_acs();
 		err = pci_for_each_dma_alias(to_pci_dev(dev),
 					     of_pci_iommu_init, &info);
+		of_pci_check_device_ats(dev, master_np);
 	} else {
 		err = of_iommu_configure_device(master_np, dev, id);
 	}