[RFC PATCH] of: Fix DMA configuration for non-DT masters

[Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>]

For PCI masters not represented in DT, we pass the OF node of their
associated host bridge to of_dma_configure(), such that they can inherit
the appropriate DMA configuration from whatever is described there.
Unfortunately, whilst this has worked for the "dma-coherent" property,
it turns out to miss the case where the host bridge node has a non-empty
"dma-ranges", since nobody is expecting the 'device' to be a bus itself.

It transpires, though, that the de-facto interface since the prototype
change in 1f5c69aa51f9 ("of: Move of_dma_configure() to device.c to help
re-use") is very clear-cut: either the master_np argument is redundant
with dev->of_node, or dev->of_node is NULL and master_np is the relevant
parent bus. Let's ratify that behaviour, then teach the whole
of_dma_configure() pipeline to cope with both cases properly.

Signed-off-by: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
---

This is what I'd consider the better fix - rather than adding yet more
special cases - which will also make it simple to handle multiple
"dma-ranges" entries with minimal further disruption. The callers now
left passing dev->of_node as 'parent' are harmless, but look a bit silly
and clearly want cleaning up - I'd be partial to renaming the existing
function and having a single-argument wrapper for the 'normal' case, e.g.:

static inline int of_dma_configure(struct device_node *dev)
{
	return of_dma_configure_parent(dev, NULL);
}

Thoughts?

Robin.

 drivers/iommu/of_iommu.c   |  7 ++++---
 drivers/of/address.c       | 37 +++++++++++++++++++++++++------------
 drivers/of/device.c        | 12 +++++++-----
 include/linux/of_address.h |  7 ++++---
 include/linux/of_device.h  |  4 ++--
 include/linux/of_iommu.h   |  4 ++--
 6 files changed, 44 insertions(+), 27 deletions(-)

diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
index 2683e9fc0dcf..35aff07bb5eb 100644
--- a/drivers/iommu/of_iommu.c
+++ b/drivers/iommu/of_iommu.c
@@ -138,21 +138,22 @@ static const struct iommu_ops
 }
 
 const struct iommu_ops *of_iommu_configure(struct device *dev,
-					   struct device_node *master_np)
+					   struct device_node *parent)
 {
 	struct of_phandle_args iommu_spec;
-	struct device_node *np;
+	struct device_node *np, *master_np;
 	const struct iommu_ops *ops = NULL;
 	int idx = 0;
 
 	if (dev_is_pci(dev))
-		return of_pci_iommu_configure(to_pci_dev(dev), master_np);
+		return of_pci_iommu_configure(to_pci_dev(dev), parent);
 
 	/*
 	 * We don't currently walk up the tree looking for a parent IOMMU.
 	 * See the `Notes:' section of
 	 * Documentation/devicetree/bindings/iommu/iommu.txt
 	 */
+	master_np = dev->of_node ? dev->of_node : parent;
 	while (!of_parse_phandle_with_args(master_np, "iommus",
 					   "#iommu-cells", idx,
 					   &iommu_spec)) {
diff --git a/drivers/of/address.c b/drivers/of/address.c
index 02b2903fe9d2..833bc17f5e55 100644
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -808,6 +808,7 @@ EXPORT_SYMBOL(of_io_request_and_map);
 /**
  * of_dma_get_range - Get DMA range info
  * @np:		device node to get DMA range info
+ * @parent:	node of device's parent bus, if @np is NULL
  * @dma_addr:	pointer to store initial DMA address of DMA range
  * @paddr:	pointer to store initial CPU address of DMA range
  * @size:	pointer to store size of DMA range
@@ -822,36 +823,48 @@ EXPORT_SYMBOL(of_io_request_and_map);
  * It returns -ENODEV if "dma-ranges" property was not found
  * for this device in DT.
  */
-int of_dma_get_range(struct device_node *np, u64 *dma_addr, u64 *paddr, u64 *size)
+int of_dma_get_range(struct device_node *np, struct device_node *parent,
+		     u64 *dma_addr, u64 *paddr, u64 *size)
 {
-	struct device_node *node = of_node_get(np);
+	struct device_node *node;
 	const __be32 *ranges = NULL;
 	int len, naddr, nsize, pna;
 	int ret = 0;
 	u64 dmaaddr;
 
-	if (!node)
-		return -EINVAL;
-
-	while (1) {
+	if (np) {
+		node = of_node_get(np);
 		naddr = of_n_addr_cells(node);
 		nsize = of_n_size_cells(node);
 		node = of_get_next_parent(node);
-		if (!node)
-			break;
+	} else if (parent) {
+		node = of_node_get(parent);
+		np = parent;
+		if (of_property_read_u32(node, "#address-cells", &naddr))
+			naddr = of_n_addr_cells(node);
+		if (of_property_read_u32(node, "#size-cells", &nsize))
+			nsize = of_n_size_cells(node);
+	} else {
+		return -EINVAL;
+	}
 
+	while (node) {
 		ranges = of_get_property(node, "dma-ranges", &len);
 
-		/* Ignore empty ranges, they imply no translation required */
-		if (ranges && len > 0)
-			break;
-
 		/*
 		 * At least empty ranges has to be defined for parent node if
 		 * DMA is supported
 		 */
 		if (!ranges)
 			break;
+
+		/* Ignore empty ranges, they imply no translation required */
+		if (len > 0)
+			break;
+
+		naddr = of_n_addr_cells(node);
+		nsize = of_n_size_cells(node);
+		node = of_get_next_parent(node);
 	}
 
 	if (!ranges) {
diff --git a/drivers/of/device.c b/drivers/of/device.c
index 9bb8518b28f2..57ec5324ed6c 100644
--- a/drivers/of/device.c
+++ b/drivers/of/device.c
@@ -73,7 +73,8 @@ int of_device_add(struct platform_device *ofdev)
 /**
  * of_dma_configure - Setup DMA configuration
  * @dev:	Device to apply DMA configuration
- * @np:		Pointer to OF node having DMA configuration
+ * @parent:	OF node of device's parent bus, if @dev is not
+ *		represented in DT (i.e. @dev->of_node is NULL)
  *
  * Try to get devices's DMA configuration from DT and update it
  * accordingly.
@@ -82,13 +83,14 @@ int of_device_add(struct platform_device *ofdev)
  * can use a platform bus notifier and handle BUS_NOTIFY_ADD_DEVICE events
  * to fix up DMA configuration.
  */
-void of_dma_configure(struct device *dev, struct device_node *np)
+void of_dma_configure(struct device *dev, struct device_node *parent)
 {
 	u64 dma_addr, paddr, size;
 	int ret;
 	bool coherent;
 	unsigned long offset;
 	const struct iommu_ops *iommu;
+	struct device_node *np = dev->of_node;
 
 	/*
 	 * Set default coherent_dma_mask to 32 bit.  Drivers are expected to
@@ -104,7 +106,7 @@ void of_dma_configure(struct device *dev, struct device_node *np)
 	if (!dev->dma_mask)
 		dev->dma_mask = &dev->coherent_dma_mask;
 
-	ret = of_dma_get_range(np, &dma_addr, &paddr, &size);
+	ret = of_dma_get_range(np, parent, &dma_addr, &paddr, &size);
 	if (ret < 0) {
 		dma_addr = offset = 0;
 		size = dev->coherent_dma_mask + 1;
@@ -132,11 +134,11 @@ void of_dma_configure(struct device *dev, struct device_node *np)
 	dev->coherent_dma_mask = DMA_BIT_MASK(ilog2(dma_addr + size));
 	*dev->dma_mask = dev->coherent_dma_mask;
 
-	coherent = of_dma_is_coherent(np);
+	coherent = of_dma_is_coherent(np ? np : parent);
 	dev_dbg(dev, "device is%sdma coherent\n",
 		coherent ? " " : " not ");
 
-	iommu = of_iommu_configure(dev, np);
+	iommu = of_iommu_configure(dev, parent);
 	dev_dbg(dev, "device is%sbehind an iommu\n",
 		iommu ? " " : " not ");
 
diff --git a/include/linux/of_address.h b/include/linux/of_address.h
index 37864734ca50..f1a507f3ae57 100644
--- a/include/linux/of_address.h
+++ b/include/linux/of_address.h
@@ -52,8 +52,8 @@ extern int of_pci_range_parser_init(struct of_pci_range_parser *parser,
 extern struct of_pci_range *of_pci_range_parser_one(
 					struct of_pci_range_parser *parser,
 					struct of_pci_range *range);
-extern int of_dma_get_range(struct device_node *np, u64 *dma_addr,
-				u64 *paddr, u64 *size);
+extern int of_dma_get_range(struct device_node *np, struct device_node *parent,
+				u64 *dma_addr, u64 *paddr, u64 *size);
 extern bool of_dma_is_coherent(struct device_node *np);
 #else /* CONFIG_OF_ADDRESS */
 static inline void __iomem *of_io_request_and_map(struct device_node *device,
@@ -95,7 +95,8 @@ static inline struct of_pci_range *of_pci_range_parser_one(
 	return NULL;
 }
 
-static inline int of_dma_get_range(struct device_node *np, u64 *dma_addr,
+static inline int of_dma_get_range(struct device_node *np,
+				struct device_node *parent, u64 *dma_addr,
 				u64 *paddr, u64 *size)
 {
 	return -ENODEV;
diff --git a/include/linux/of_device.h b/include/linux/of_device.h
index c12dace043f3..bcd2b6fbeef3 100644
--- a/include/linux/of_device.h
+++ b/include/linux/of_device.h
@@ -55,7 +55,7 @@ static inline struct device_node *of_cpu_device_node_get(int cpu)
 	return of_node_get(cpu_dev->of_node);
 }
 
-void of_dma_configure(struct device *dev, struct device_node *np);
+void of_dma_configure(struct device *dev, struct device_node *parent);
 #else /* CONFIG_OF */
 
 static inline int of_driver_match_device(struct device *dev,
@@ -103,7 +103,7 @@ static inline struct device_node *of_cpu_device_node_get(int cpu)
 {
 	return NULL;
 }
-static inline void of_dma_configure(struct device *dev, struct device_node *np)
+static inline void of_dma_configure(struct device *dev, struct device_node *parent)
 {}
 #endif /* CONFIG_OF */
 
diff --git a/include/linux/of_iommu.h b/include/linux/of_iommu.h
index 13394ac83c66..c02b62e8e6ed 100644
--- a/include/linux/of_iommu.h
+++ b/include/linux/of_iommu.h
@@ -12,7 +12,7 @@ extern int of_get_dma_window(struct device_node *dn, const char *prefix,
 			     size_t *size);
 
 extern const struct iommu_ops *of_iommu_configure(struct device *dev,
-					struct device_node *master_np);
+					struct device_node *parent);
 
 #else
 
@@ -24,7 +24,7 @@ static inline int of_get_dma_window(struct device_node *dn, const char *prefix,
 }
 
 static inline const struct iommu_ops *of_iommu_configure(struct device *dev,
-					 struct device_node *master_np)
+					 struct device_node *parent)
 {
 	return NULL;
 }
-- 
2.11.0.dirty