regulator: core: Parse coupled regulators properties

On Odroid XU3/4 and other Exynos5422 based boards there is a case, that
different devices on the board are supplied by different regulators
with non-fixed voltages. If one of these devices temporarily requires
higher voltage, there might occur a situation that the spread between
devices' voltages is so high, that there is a risk of changing
'high' and 'low' states on the interconnection between devices powered
by those regulators.

Add new structure "coupling_desc" to regulator_dev, which contains
pointers to all coupled regulators including the owner of the structure,
number of coupled regulators and counter of currently resolved
regulators.

Add of_functions to parse all data needed in regulator coupling.
Provide method to check DTS data consistency. Check if each coupled
regulator's max_spread is equal and if their lists of regulators match.

Signed-off-by: Maciej Purski <m.purski@samsung.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/of_regulator.c

@@ -166,6 +166,10 @@ static void of_get_regulation_constraints(struct device_node *np,
 	if (!of_property_read_u32(np, "regulator-system-load", &pval))
 		constraints->system_load = pval;
 
+	if (!of_property_read_u32(np, "regulator-coupled-max-spread",
+				  &pval))
+		constraints->max_spread = pval;
+
 	constraints->over_current_protection = of_property_read_bool(np,
 					"regulator-over-current-protection");
 
@@ -435,3 +439,150 @@ struct regulator_dev *of_find_regulator_by_node(struct device_node *np)
 
 	return dev ? dev_to_rdev(dev) : NULL;
 }
+
+/*
+ * Returns number of regulators coupled with rdev.
+ */
+int of_get_n_coupled(struct regulator_dev *rdev)
+{
+	struct device_node *node = rdev->dev.of_node;
+	int n_phandles;
+
+	n_phandles = of_count_phandle_with_args(node,
+						"regulator-coupled-with",
+						NULL);
+
+	return (n_phandles > 0) ? n_phandles : 0;
+}
+
+/* Looks for "to_find" device_node in src's "regulator-coupled-with" property */
+static bool of_coupling_find_node(struct device_node *src,
+				  struct device_node *to_find)
+{
+	int n_phandles, i;
+	bool found = false;
+
+	n_phandles = of_count_phandle_with_args(src,
+						"regulator-coupled-with",
+						NULL);
+
+	for (i = 0; i < n_phandles; i++) {
+		struct device_node *tmp = of_parse_phandle(src,
+					   "regulator-coupled-with", i);
+
+		if (!tmp)
+			break;
+
+		/* found */
+		if (tmp == to_find)
+			found = true;
+
+		of_node_put(tmp);
+
+		if (found)
+			break;
+	}
+
+	return found;
+}
+
+/**
+ * of_check_coupling_data - Parse rdev's coupling properties and check data
+ *			    consistency
+ * @rdev - pointer to regulator_dev whose data is checked
+ *
+ * Function checks if all the following conditions are met:
+ * - rdev's max_spread is greater than 0
+ * - all coupled regulators have the same max_spread
+ * - all coupled regulators have the same number of regulator_dev phandles
+ * - all regulators are linked to each other
+ *
+ * Returns true if all conditions are met.
+ */
+bool of_check_coupling_data(struct regulator_dev *rdev)
+{
+	int max_spread = rdev->constraints->max_spread;
+	struct device_node *node = rdev->dev.of_node;
+	int n_phandles = of_get_n_coupled(rdev);
+	struct device_node *c_node;
+	int i;
+	bool ret = true;
+
+	if (max_spread <= 0) {
+		dev_err(&rdev->dev, "max_spread value invalid\n");
+		return false;
+	}
+
+	/* iterate over rdev's phandles */
+	for (i = 0; i < n_phandles; i++) {
+		int c_max_spread, c_n_phandles;
+
+		c_node = of_parse_phandle(node,
+					  "regulator-coupled-with", i);
+
+		if (!c_node)
+			ret = false;
+
+		c_n_phandles = of_count_phandle_with_args(c_node,
+							  "regulator-coupled-with",
+							  NULL);
+
+		if (c_n_phandles != n_phandles) {
+			dev_err(&rdev->dev, "number of couped reg phandles mismatch\n");
+			ret = false;
+			goto clean;
+		}
+
+		if (of_property_read_u32(c_node, "regulator-coupled-max-spread",
+					 &c_max_spread)) {
+			ret = false;
+			goto clean;
+		}
+
+		if (c_max_spread != max_spread) {
+			dev_err(&rdev->dev,
+				"coupled regulators max_spread mismatch\n");
+			ret = false;
+			goto clean;
+		}
+
+		if (!of_coupling_find_node(c_node, node)) {
+			dev_err(&rdev->dev, "missing 2-way linking for coupled regulators\n");
+			ret = false;
+		}
+
+clean:
+		of_node_put(c_node);
+		if (!ret)
+			break;
+	}
+
+	return ret;
+}
+
+/**
+ * of_parse_coupled regulator - Get regulator_dev pointer from rdev's property
+ * @rdev: Pointer to regulator_dev, whose DTS is used as a source to parse
+ *	  "regulator-coupled-with" property
+ * @index: Index in phandles array
+ *
+ * Returns the regulator_dev pointer parsed from DTS. If it has not been yet
+ * registered, returns NULL
+ */
+struct regulator_dev *of_parse_coupled_regulator(struct regulator_dev *rdev,
+						 int index)
+{
+	struct device_node *node = rdev->dev.of_node;
+	struct device_node *c_node;
+	struct regulator_dev *c_rdev;
+
+	c_node = of_parse_phandle(node, "regulator-coupled-with", index);
+	if (!c_node)
+		return NULL;
+
+	c_rdev = of_find_regulator_by_node(c_node);
+
+	of_node_put(c_node);
+
+	return c_rdev;
+}