dm: core: support reading a single indexed u64 value

Add helper function to allow reading a single indexed u64 value from a
device-tree property containing multiple u64 values, that is an array of
u64's.

Co-developed-by: Ashok Reddy Soma <ashok.reddy.soma@amd.com>
Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@amd.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/08043c8d204d0068f04c27de86afe78c75c50b69.1692956263.git.michal.simek@amd.com
diff --git a/arch/sandbox/dts/test.dts b/arch/sandbox/dts/test.dts
index 63fda15..d4693e3 100644
--- a/arch/sandbox/dts/test.dts
+++ b/arch/sandbox/dts/test.dts
@@ -301,6 +301,7 @@
 		uint-value = <(-1234)>;
 		int64-value = /bits/ 64 <0x1111222233334444>;
 		int-array = <5678 9123 4567>;
+		int64-array = /bits/ 64 <0x1111222233334444 0x4444333322221111>;
 		str-value = "test string";
 		interrupts-extended = <&irq 3 0>;
 		acpi,name = "GHIJ";
diff --git a/drivers/core/of_access.c b/drivers/core/of_access.c
index 57f1044..1bb4d8e 100644
--- a/drivers/core/of_access.c
+++ b/drivers/core/of_access.c
@@ -570,26 +570,34 @@
 	return 0;
 }
 
-int of_read_u64(const struct device_node *np, const char *propname, u64 *outp)
+int of_read_u64_index(const struct device_node *np, const char *propname,
+		      int index, u64 *outp)
 {
 	const __be64 *val;
 
 	debug("%s: %s: ", __func__, propname);
 	if (!np)
 		return -EINVAL;
-	val = of_find_property_value_of_size(np, propname, sizeof(*outp));
+
+	val = of_find_property_value_of_size(np, propname,
+					     sizeof(*outp) * (index + 1));
 	if (IS_ERR(val)) {
 		debug("(not found)\n");
 		return PTR_ERR(val);
 	}
 
-	*outp = be64_to_cpup(val);
+	*outp = be64_to_cpup(val + index);
 	debug("%#llx (%lld)\n", (unsigned long long)*outp,
-              (unsigned long long)*outp);
+	      (unsigned long long)*outp);
 
 	return 0;
 }
 
+int of_read_u64(const struct device_node *np, const char *propname, u64 *outp)
+{
+	return of_read_u64_index(np, propname, 0, outp);
+}
+
 int of_property_match_string(const struct device_node *np, const char *propname,
 			     const char *string)
 {
diff --git a/drivers/core/ofnode.c b/drivers/core/ofnode.c
index a4dc9bd..8311282 100644
--- a/drivers/core/ofnode.c
+++ b/drivers/core/ofnode.c
@@ -344,6 +344,36 @@
 	return 0;
 }
 
+int ofnode_read_u64_index(ofnode node, const char *propname, int index,
+			  u64 *outp)
+{
+	const fdt64_t *cell;
+	int len;
+
+	assert(ofnode_valid(node));
+
+	if (ofnode_is_np(node))
+		return of_read_u64_index(ofnode_to_np(node), propname, index,
+					 outp);
+
+	cell = fdt_getprop(ofnode_to_fdt(node), ofnode_to_offset(node),
+			   propname, &len);
+	if (!cell) {
+		debug("(not found)\n");
+		return -EINVAL;
+	}
+
+	if (len < (sizeof(u64) * (index + 1))) {
+		debug("(not large enough)\n");
+		return -EOVERFLOW;
+	}
+
+	*outp = fdt64_to_cpu(cell[index]);
+	debug("%#llx (%lld)\n", *outp, *outp);
+
+	return 0;
+}
+
 u32 ofnode_read_u32_index_default(ofnode node, const char *propname, int index,
 				  u32 def)
 {
diff --git a/include/dm/of_access.h b/include/dm/of_access.h
index c556a18..9361d0a 100644
--- a/include/dm/of_access.h
+++ b/include/dm/of_access.h
@@ -334,6 +334,25 @@
 		      int index, u32 *outp);
 
 /**
+ * of_read_u64_index() - Find and read a 64-bit value from a multi-value
+ *                       property
+ *
+ * @np:		device node from which the property value is to be read.
+ * @propname:	name of the property to be searched.
+ * @index:	index of the u32 in the list of values
+ * @outp:	pointer to return value, modified only if return value is 0.
+ *
+ * Search for a property in a device node and read a 64-bit value from
+ * it.
+ *
+ * Return:
+ *   0 on success, -EINVAL if the property does not exist, or -EOVERFLOW if the
+ *   property data isn't large enough.
+ */
+int of_read_u64_index(const struct device_node *np, const char *propname,
+		      int index, u64 *outp);
+
+/**
  * of_read_u64() - Find and read a 64-bit integer from a property
  *
  * Search for a property in a device node and read a 64-bit value from
diff --git a/include/dm/ofnode.h b/include/dm/ofnode.h
index 0f38b3e..0a85db3 100644
--- a/include/dm/ofnode.h
+++ b/include/dm/ofnode.h
@@ -435,6 +435,18 @@
 			  u32 *outp);
 
 /**
+ * ofnode_read_u64_index() - Read a 64-bit integer from a multi-value property
+ *
+ * @node:	valid node reference to read property from
+ * @propname:	name of the property to read from
+ * @index:	index of the integer to return
+ * @outp:	place to put value (if found)
+ * Return: 0 if OK, -ve on error
+ */
+int ofnode_read_u64_index(ofnode node, const char *propname, int index,
+			  u64 *outp);
+
+/**
  * ofnode_read_s32() - Read a 32-bit integer from a property
  *
  * @node:	valid node reference to read property from
diff --git a/test/dm/ofnode.c b/test/dm/ofnode.c
index 6fbebc7..b74f5c2 100644
--- a/test/dm/ofnode.c
+++ b/test/dm/ofnode.c
@@ -967,6 +967,14 @@
 	ut_asserteq_64(0x1111222233334444, val);
 	ut_asserteq(-EINVAL, ofnode_read_u64(node, "missing", &val));
 
+	ut_assertok(ofnode_read_u64_index(node, "int64-array", 0, &val));
+	ut_asserteq_64(0x1111222233334444, val);
+	ut_assertok(ofnode_read_u64_index(node, "int64-array", 1, &val));
+	ut_asserteq_64(0x4444333322221111, val);
+	ut_asserteq(-EOVERFLOW,
+		    ofnode_read_u64_index(node, "int64-array", 2, &val));
+	ut_asserteq(-EINVAL, ofnode_read_u64_index(node, "missing", 0, &val));
+
 	return 0;
 }
 DM_TEST(dm_test_ofnode_u64, UT_TESTF_SCAN_FDT);