Hi Bjorn,

On 15/04/16 17:14, Bjorn Helgaas wrote:

On Thu, Apr 14, 2016 at 06:25:41PM +0100, Lorenzo Pieralisi wrote:

quoted

On DT based systems, the of_dma_configure() API implements DMA configuration
for a given device. On ACPI systems an API equivalent to of_dma_configure()
is missing which implies that it is currently not possible to set-up DMA
operations for devices through the ACPI generic kernel layer.

This patch fills the gap by introducing acpi_dma_configure/deconfigure()
calls, that carry out IOMMU configuration through IORT (on systems where
it is present) and call arch_setup_dma_ops(...) with the retrieved
parameters.

The DMA range size passed to arch_setup_dma_ops() is sized according
to the device coherent_dma_mask (starting at address 0x0), mirroring the
DT probing path behaviour when a dma-ranges property is not provided
for the device being probed; this changes the current arch_setup_dma_ops()
call parameters in the ACPI probing case, but since arch_setup_dma_ops()
is a NOP on all architectures but ARM/ARM64 this patch does not change
the current kernel behaviour on them.

This patch updates ACPI and PCI core code to use the newly introduced
acpi_dma_configure function, providing the same functionality
as of_dma_configure on ARM systems and leaving behaviour unchanged
for all other arches.

Signed-off-by: Lorenzo Pieralisi <redacted>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Tomasz Nowicki <redacted>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: "Rafael J. Wysocki" <redacted>

There's only a tiny PCI change in this series, so I assume somebody
else will merge all this.  Here's my ack for the PCI part:

Acked-by: Bjorn Helgaas <bhelgaas@google.com>	# for drivers/pci/probe.c change

One question on use of pci_for_each_dma_alias() below.

quoted

+static int __get_pci_rid(struct pci_dev *pdev, u16 alias, void *data)
+{
+	u32 *rid = data;
+
+	*rid = alias;
+	return 0;
+}
+
+/**
+ * iort_iommu_configure - Set-up IOMMU configuration for a device.
+ *
+ * @dev: device that requires IOMMU set-up
+ *
+ * Returns: iommu_ops pointer on configuration success
+ *          NULL on configuration failure
+ */
+struct iommu_ops *iort_iommu_configure(struct device *dev)
+{
+	struct acpi_iort_node *node, *parent;
+	struct iommu_ops *ops = NULL;
+	struct iommu_fwspec fwspec;
+	struct iort_iommu_node *iommu_node;
+	u32 rid = 0, devid = 0;
+
+	if (dev_is_pci(dev)) {
+		struct pci_bus *bus = to_pci_dev(dev)->bus;
+
+		pci_for_each_dma_alias(to_pci_dev(dev), __get_pci_rid,
+				       &rid);

You end up with only the last DMA alias in "rid".  Is it really true
that you only need to call iort_dev_map_rid() for one of the aliases?

Indeed - all we care about is what things look like by the time they 
come out of the root complex on their way to the the IOMMU, so whatever 
intermediate aliasing _within_ the PCI bus might happen along the way 
doesn't actually matter.

Robin.

quoted

+		node = iort_scan_node(ACPI_IORT_NODE_PCI_ROOT_COMPLEX,
+				      iort_find_dev_callback, &bus->dev);
+	} else
+		node = iort_scan_node(ACPI_IORT_NODE_NAMED_COMPONENT,
+				      iort_find_dev_callback, dev);
+
+	if (!node)
+		return NULL;
+
+	iort_dev_map_rid(node, rid, &devid, ACPI_IORT_NODE_SMMU);
+
+	parent = iort_find_parent_node(node, ACPI_IORT_NODE_SMMU);
+
+	if (!parent)
+		return NULL;
+
+	iommu_node = iort_iommu_get_node(parent);
+	ops = iommu_node->ops;
+
+	fwspec.fwnode = iommu_node->fwnode;
+	fwspec.param_count = 1;
+	fwspec.param[0] = devid;
+
+	if (!ops || !ops->fw_xlate || ops->fw_xlate(dev, &fwspec))
+		return NULL;
+
+	return ops;
+}

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