[RFC v1 PATCH 1/2] of/pci: add of_pci_dma_configure() update dma configuration

[Murali Karicheri <m-karicheri2@ti.com>]

Add of_pci_dma_configure() to allow updating the dma configuration
of the pci device using the configuration from the parent of
the root bridge device.

Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
---
 drivers/of/of_pci.c    |   71 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/of_pci.h |   12 ++++++++
 2 files changed, 83 insertions(+)

diff --git a/drivers/of/of_pci.c b/drivers/of/of_pci.c
index 88471d3..966b418 100644
--- a/drivers/of/of_pci.c
+++ b/drivers/of/of_pci.c
@@ -229,6 +229,77 @@ parse_failed:
 	return err;
 }
 EXPORT_SYMBOL_GPL(of_pci_get_host_bridge_resources);
+
+/**
+ * of_get_pci_root_bridge_parent - Helper function to get the OF node of
+ *		the root bridge's parent
+ * @dev: ptr to pci_dev struct of the pci device
+ *
+ * This function will traverse the bus up to the root bus starting with
+ * the child and return the of node ptr to bridge device's parent device.
+ */
+struct device_node *of_get_pci_root_bridge_parent(struct pci_dev *dev)
+{
+	struct pci_bus *bus = dev->bus;
+	struct device *bridge;
+
+	while (!pci_is_root_bus(bus))
+		bus = bus->parent;
+	bridge = bus->bridge;
+
+	return bridge->parent->of_node;
+}
+EXPORT_SYMBOL_GPL(of_get_pci_root_bridge_parent);
+
+/**
+ * of_pci_dma_configure - Setup DMA configuration
+ * @dev: ptr to pci_dev struct of the pci device
+ *
+ * Try to get PCI devices's DMA configuration from DT and update it
+ * accordingly. This is similar to of_dma_configure() in of/platform.c
+ */
+void of_pci_dma_configure(struct pci_dev *pci_dev)
+{
+	struct device *dev = &pci_dev->dev;
+	u64 dma_addr, paddr, size;
+	struct device_node *parent_np;
+	unsigned long offset;
+	bool coherent;
+	int ret;
+
+	parent_np = of_get_pci_root_bridge_parent(pci_dev);
+
+	/*
+	 * Set default dma-mask to 32 bit. Drivers are expected to setup
+	 * the correct supported dma_mask.
+	 */
+	dev->coherent_dma_mask = DMA_BIT_MASK(32);
+
+	/*
+	 * Set it to coherent_dma_mask by default if the architecture
+	 * code has not set it.
+	 */
+	if (!dev->dma_mask)
+		dev->dma_mask = &dev->coherent_dma_mask;
+
+	ret = of_dma_get_range(parent_np, &dma_addr, &paddr, &size);
+	if (ret < 0) {
+		dma_addr = offset = 0;
+		size = dev->coherent_dma_mask;
+	} else {
+		offset = PFN_DOWN(paddr - dma_addr);
+		dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", dev->dma_pfn_offset);
+	}
+	dev->dma_pfn_offset = offset;
+
+	coherent = of_dma_is_coherent(parent_np);
+	dev_dbg(dev, "device is%sdma coherent\n",
+		coherent ? " " : " not ");
+
+	arch_setup_dma_ops(dev, dma_addr, size, NULL, coherent);
+}
+EXPORT_SYMBOL_GPL(of_pci_dma_configure);
+
 #endif /* CONFIG_OF_ADDRESS */
 
 #ifdef CONFIG_PCI_MSI
diff --git a/include/linux/of_pci.h b/include/linux/of_pci.h
index ce0e5ab..0465a2a 100644
--- a/include/linux/of_pci.h
+++ b/include/linux/of_pci.h
@@ -16,6 +16,8 @@ int of_pci_get_devfn(struct device_node *np);
 int of_irq_parse_and_map_pci(const struct pci_dev *dev, u8 slot, u8 pin);
 int of_pci_parse_bus_range(struct device_node *node, struct resource *res);
 int of_get_pci_domain_nr(struct device_node *node);
+struct device_node *of_get_pci_root_bridge_parent(struct pci_dev *dev);
+void of_pci_dma_configure(struct pci_dev *pci_dev);
 #else
 static inline int of_irq_parse_pci(const struct pci_dev *pdev, struct of_phandle_args *out_irq)
 {
@@ -50,6 +52,16 @@ of_get_pci_domain_nr(struct device_node *node)
 {
 	return -1;
 }
+
+static inline struct device_node
+*of_get_pci_root_bridge_parent(struct pci_dev *dev)
+{
+	return NULL;
+}
+
+static inline void of_pci_dma_configure(struct pci_dev *pci_dev)
+{
+}
 #endif
 
 #if defined(CONFIG_OF_ADDRESS)
-- 
1.7.9.5