regulator: core: Add support to limit min_uV during system startup

Now a regulator device can supply multiple consumers at the same time,
if a consumer starts and set a low voltage, another consumer doesn't
start in kernel but has been set a high frequency in bootloader will
abort.

This patch Adds support to limit min_uV during kernel startup to make
sure the voltage can suit the needs of all consumers.

Change-Id: Ibd16a8e44916798021e2470c90a8e3488df206f4
Signed-off-by: Finley Xiao <finley.xiao@rock-chips.com>

Author: finley1226

Documentation/devicetree/bindings/regulator/regulator.txt

@@ -5,6 +5,8 @@ Optional properties:
 - regulator-min-microvolt: smallest voltage consumers may set
 - regulator-max-microvolt: largest voltage consumers may set
 - regulator-microvolt-offset: Offset applied to voltages to compensate for voltage drops
+- regulator-early-min-microvolt: minimum voltage during system startup, make sure we
+  select a voltage that suits the needs of all regulator consumers
 - regulator-min-microamp: smallest current consumers may set
 - regulator-max-microamp: largest current consumers may set
 - regulator-input-current-limit-microamp: maximum input current regulator allows

drivers/regulator/core.c

@@ -56,6 +56,7 @@ static DEFINE_MUTEX(regulator_list_mutex);
 static LIST_HEAD(regulator_map_list);
 static LIST_HEAD(regulator_ena_gpio_list);
 static LIST_HEAD(regulator_supply_alias_list);
+static LIST_HEAD(regulator_early_min_volt_list);
 static bool has_full_constraints;
 
 static struct dentry *debugfs_root;
@@ -4224,6 +4225,26 @@ static inline void rdev_init_debugfs(struct regulator_dev *rdev)
 
 #endif
 
+static void rdev_init_early_min_volt(struct regulator_dev *rdev)
+{
+	struct regulator *regulator;
+
+	if (!rdev->constraints->early_min_uV)
+		return;
+
+	regulator = regulator_get(NULL, rdev_get_name(rdev));
+	if (IS_ERR(regulator)) {
+		rdev_err(rdev, "regulator get failed, ret=%ld\n",
+			 PTR_ERR(regulator));
+		return;
+	}
+
+	regulator->min_uV = rdev->constraints->early_min_uV;
+	regulator->max_uV = rdev->constraints->max_uV;
+
+	list_add(&regulator->early_min_list, &regulator_early_min_volt_list);
+}
+
 static int regulator_register_resolve_supply(struct device *dev, void *data)
 {
 	struct regulator_dev *rdev = dev_to_rdev(dev);
@@ -4391,6 +4412,7 @@ regulator_register(const struct regulator_desc *regulator_desc,
 
 	dev_set_drvdata(&rdev->dev, rdev);
 	rdev_init_debugfs(rdev);
+	rdev_init_early_min_volt(rdev);
 
 	/* try to resolve regulators supply since a new one was registered */
 	class_for_each_device(&regulator_class, NULL, NULL,
@@ -4830,6 +4852,28 @@ static int __init regulator_late_cleanup(struct device *dev, void *data)
 	return 0;
 }
 
+static void __init regulator_release_early_min_volt(void)
+{
+	struct regulator *regulator, *n;
+	struct regulator_dev *rdev;
+
+	if (list_empty(&regulator_early_min_volt_list))
+		return;
+
+	list_for_each_entry_safe(regulator, n, &regulator_early_min_volt_list,
+				 early_min_list) {
+		rdev = regulator->rdev;
+		regulator->min_uV = 0;
+		regulator->max_uV = 0;
+		if (regulator_set_voltage(regulator, regulator->min_uV,
+					  regulator->max_uV))
+			rdev_err(regulator->rdev, "set voltage(%d, %d) failed\n",
+				 regulator->min_uV, regulator->max_uV);
+		list_del(&regulator->early_min_list);
+		regulator_put(regulator);
+	}
+}
+
 static int __init regulator_init_complete(void)
 {
 	/*
@@ -4849,6 +4893,8 @@ static int __init regulator_init_complete(void)
 	class_for_each_device(&regulator_class, NULL, NULL,
 			      regulator_late_cleanup);
 
+	regulator_release_early_min_volt();
+
 	return 0;
 }
 late_initcall_sync(regulator_init_complete);

drivers/regulator/internal.h

@@ -24,6 +24,7 @@
 struct regulator {
 	struct device *dev;
 	struct list_head list;
+	struct list_head early_min_list;
 	unsigned int always_on:1;
 	unsigned int bypass:1;
 	int uA_load;

drivers/regulator/of_regulator.c

@@ -42,6 +42,9 @@ static void of_get_regulation_constraints(struct device_node *np,
 	if (!of_property_read_u32(np, "regulator-max-microvolt", &pval))
 		constraints->max_uV = pval;
 
+	if (!of_property_read_u32(np, "regulator-early-min-microvolt", &pval))
+		constraints->early_min_uV = pval;
+
 	/* Voltage change possible? */
 	if (constraints->min_uV != constraints->max_uV)
 		constraints->valid_ops_mask |= REGULATOR_CHANGE_VOLTAGE;

include/linux/regulator/machine.h

@@ -80,6 +80,9 @@ struct regulator_state {
  * @uV_offset: Offset applied to voltages from consumer to compensate for
  *             voltage drops.
  *
+ * @early_min_uV: Minimum voltage during system startup, make sure we select
+ *                a voltage that suits the needs of all regulator consumers.
+ *
  * @min_uA: Smallest current consumers may set.
  * @max_uA: Largest current consumers may set.
  * @ilim_uA: Maximum input current.
@@ -126,6 +129,9 @@ struct regulation_constraints {
 	int min_uV;
 	int max_uV;
 
+	/* Minimum voltage during system startup */
+	int early_min_uV;
+
 	int uV_offset;
 
 	/* current output range (inclusive) - for current control */