[PATCH] of: Allow busses with #size-cells=0

[Stephen Warren]

From: Stephen Warren <swarren at nvidia.com>

It's quite legitimate for a DT node to specify #size-cells=0. One example
is a node that's used to collect a number of non-memory-mapped devices.
In that scenario, there may be multiple child nodes with the same name
(type) thus necessitating the use of unit addresses in node names, and
reg properties:

/ {
	regulators {
		compatible = "simple-bus";
		#address-cells = <1>;
		#size-cells = <0>;

		regulator at 0 {
			compatible = "regulator-fixed";
			reg = <0>;
			...
		};

		regulator at 1 {
			compatible = "regulator-fixed";
			reg = <1>;
			...
		};

		...
	};
};

However, #size-cells=0 prevents translation of reg property values into
the parent node's address space. In turn, this triggers the kernel to
emit error messages during boot, such as:

    prom_parse: Bad cell count for /regulators/regulator at 0

To prevent printing these error messages for legitimate DT content, a
number of changes are made:

1) of_get_address()/of_get_pci_address() are modified only to validate
   the value of #address-cells, and not #size-cells.

2) of_can_translate_address() is added to indicate whether address
   translation is possible.

3) of_device_make_bus_id() is modified to name devices based on the
   translated address only where possible, and otherwise fall back to
   using the (first cell of the) raw untranslated address.

4) of_device_alloc() is modified to create memory resources for a device
   only if the address can be translated into the CPU's address space.

Signed-off-by: Stephen Warren <swarren at nvidia.com>
---
 drivers/of/address.c       |   27 +++++++++++++++++++++++----
 drivers/of/platform.c      |   16 +++++++++++++---
 include/linux/of_address.h |    1 +
 3 files changed, 37 insertions(+), 7 deletions(-)

diff --git a/drivers/of/address.c b/drivers/of/address.c
index 7e262a6..7a07751 100644
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -9,8 +9,8 @@
 
 /* Max address size we deal with */
 #define OF_MAX_ADDR_CELLS	4
-#define OF_CHECK_COUNTS(na, ns)	((na) > 0 && (na) <= OF_MAX_ADDR_CELLS && \
-			(ns) > 0)
+#define OF_CHECK_ADDR_COUNT(na)	((na) > 0 && (na) <= OF_MAX_ADDR_CELLS)
+#define OF_CHECK_COUNTS(na, ns)	(OF_CHECK_ADDR_COUNT(na) && (ns) > 0)
 
 static struct of_bus *of_match_bus(struct device_node *np);
 static int __of_address_to_resource(struct device_node *dev,
@@ -182,7 +182,7 @@ const __be32 *of_get_pci_address(struct device_node *dev, int bar_no, u64 *size,
 	}
 	bus->count_cells(dev, &na, &ns);
 	of_node_put(parent);
-	if (!OF_CHECK_COUNTS(na, ns))
+	if (!OF_CHECK_ADDR_COUNT(na))
 		return NULL;
 
 	/* Get "reg" or "assigned-addresses" property */
@@ -490,6 +490,25 @@ u64 of_translate_dma_address(struct device_node *dev, const __be32 *in_addr)
 }
 EXPORT_SYMBOL(of_translate_dma_address);
 
+bool of_can_translate_address(struct device_node *dev)
+{
+	struct device_node *parent;
+	struct of_bus *bus;
+	int na, ns;
+
+	parent = of_get_parent(dev);
+	if (parent == NULL)
+		return false;
+
+	bus = of_match_bus(parent);
+	bus->count_cells(dev, &na, &ns);
+
+	of_node_put(parent);
+
+	return OF_CHECK_COUNTS(na, ns);
+}
+EXPORT_SYMBOL(of_can_translate_address);
+
 const __be32 *of_get_address(struct device_node *dev, int index, u64 *size,
 		    unsigned int *flags)
 {
@@ -506,7 +525,7 @@ const __be32 *of_get_address(struct device_node *dev, int index, u64 *size,
 	bus = of_match_bus(parent);
 	bus->count_cells(dev, &na, &ns);
 	of_node_put(parent);
-	if (!OF_CHECK_COUNTS(na, ns))
+	if (!OF_CHECK_ADDR_COUNT(na))
 		return NULL;
 
 	/* Get "reg" or "assigned-addresses" property */
diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index e44f8c2..9bdeaf3 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -78,6 +78,7 @@ void of_device_make_bus_id(struct device *dev)
 	struct device_node *node = dev->of_node;
 	const u32 *reg;
 	u64 addr;
+	const __be32 *addrp;
 	int magic;
 
 #ifdef CONFIG_PPC_DCR
@@ -105,7 +106,15 @@ void of_device_make_bus_id(struct device *dev)
 	 */
 	reg = of_get_property(node, "reg", NULL);
 	if (reg) {
-		addr = of_translate_address(node, reg);
+		if (of_can_translate_address(node)) {
+			addr = of_translate_address(node, reg);
+		} else {
+			addrp = of_get_address(node, 0, NULL, NULL);
+			if (addrp)
+				addr = of_read_number(addrp, 1);
+			else
+				addr = OF_BAD_ADDR;
+		}
 		if (addr != OF_BAD_ADDR) {
 			dev_set_name(dev, "%llx.%s",
 				     (unsigned long long)addr, node->name);
@@ -140,8 +149,9 @@ struct platform_device *of_device_alloc(struct device_node *np,
 		return NULL;
 
 	/* count the io and irq resources */
-	while (of_address_to_resource(np, num_reg, &temp_res) == 0)
-		num_reg++;
+	if (of_can_translate_address(np))
+		while (of_address_to_resource(np, num_reg, &temp_res) == 0)
+			num_reg++;
 	num_irq = of_irq_count(np);
 
 	/* Populate the resource table */
diff --git a/include/linux/of_address.h b/include/linux/of_address.h
index 01b925a..c3cdc10 100644
--- a/include/linux/of_address.h
+++ b/include/linux/of_address.h
@@ -6,6 +6,7 @@
 
 #ifdef CONFIG_OF_ADDRESS
 extern u64 of_translate_address(struct device_node *np, const __be32 *addr);
+extern bool of_can_translate_address(struct device_node *dev);
 extern int of_address_to_resource(struct device_node *dev, int index,
 				  struct resource *r);
 extern struct device_node *of_find_matching_node_by_address(
-- 
1.7.0.4