[PATCH v3 1/5] regulator: core: Introduce API for regulators coupling customization

[Dmitry Osipenko <digetx@gmail.com>]

Right now regulator core supports only one type of regulators coupling,
the "voltage max-spread" which keeps voltages of coupled regulators in a
given range from each other. A more sophisticated coupling may be required
in practice, one example is the NVIDIA Tegra SoCs which besides the
max-spreading have other restrictions that must be adhered. Introduce API
that allow platforms to provide their own customized coupling algorithms.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/regulator/core.c          | 136 +++++++++++++++++++++++++-----
 drivers/regulator/of_regulator.c  |  63 +++++++++-----
 include/linux/regulator/coupler.h |  62 ++++++++++++++
 include/linux/regulator/driver.h  |   6 +-
 include/linux/regulator/machine.h |   2 +-
 5 files changed, 225 insertions(+), 44 deletions(-)
 create mode 100644 include/linux/regulator/coupler.h

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index eb5670d7dcbb..98912f1c808d 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -22,6 +22,7 @@
 #include <linux/regmap.h>
 #include <linux/regulator/of_regulator.h>
 #include <linux/regulator/consumer.h>
+#include <linux/regulator/coupler.h>
 #include <linux/regulator/driver.h>
 #include <linux/regulator/machine.h>
 #include <linux/module.h>
@@ -49,6 +50,7 @@ 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_coupler_list);
 static bool has_full_constraints;
 
 static struct dentry *debugfs_root;
@@ -3433,11 +3435,10 @@ static int regulator_get_optimal_voltage(struct regulator_dev *rdev,
 	struct coupling_desc *c_desc = &rdev->coupling_desc;
 	struct regulator_dev **c_rdevs = c_desc->coupled_rdevs;
 	struct regulation_constraints *constraints = rdev->constraints;
-	int max_spread = constraints->max_spread;
 	int desired_min_uV = 0, desired_max_uV = INT_MAX;
 	int max_current_uV = 0, min_current_uV = INT_MAX;
 	int highest_min_uV = 0, target_uV, possible_uV;
-	int i, ret;
+	int i, ret, max_spread;
 	bool done;
 
 	*current_uV = -1;
@@ -3491,6 +3492,8 @@ static int regulator_get_optimal_voltage(struct regulator_dev *rdev,
 		}
 	}
 
+	max_spread = constraints->max_spread[0];
+
 	/*
 	 * Let target_uV be equal to the desired one if possible.
 	 * If not, set it to minimum voltage, allowed by other coupled
@@ -3572,9 +3575,11 @@ static int regulator_balance_voltage(struct regulator_dev *rdev,
 	struct regulator_dev **c_rdevs;
 	struct regulator_dev *best_rdev;
 	struct coupling_desc *c_desc = &rdev->coupling_desc;
+	struct regulator_coupler *coupler = c_desc->coupler;
 	int i, ret, n_coupled, best_min_uV, best_max_uV, best_c_rdev;
-	bool best_c_rdev_done, c_rdev_done[MAX_COUPLED];
 	unsigned int delta, best_delta;
+	unsigned long c_rdev_done = 0;
+	bool best_c_rdev_done;
 
 	c_rdevs = c_desc->coupled_rdevs;
 	n_coupled = c_desc->n_coupled;
@@ -3591,8 +3596,9 @@ static int regulator_balance_voltage(struct regulator_dev *rdev,
 		return -EPERM;
 	}
 
-	for (i = 0; i < n_coupled; i++)
-		c_rdev_done[i] = false;
+	/* Invoke custom balancer for customized couplers */
+	if (coupler && coupler->balance_voltage)
+		return coupler->balance_voltage(coupler, rdev, state);
 
 	/*
 	 * Find the best possible voltage change on each loop. Leave the loop
@@ -3619,7 +3625,7 @@ static int regulator_balance_voltage(struct regulator_dev *rdev,
 			 */
 			int optimal_uV = 0, optimal_max_uV = 0, current_uV = 0;
 
-			if (c_rdev_done[i])
+			if (test_bit(i, &c_rdev_done))
 				continue;
 
 			ret = regulator_get_optimal_voltage(c_rdevs[i],
@@ -3654,7 +3660,8 @@ static int regulator_balance_voltage(struct regulator_dev *rdev,
 		if (ret < 0)
 			goto out;
 
-		c_rdev_done[best_c_rdev] = best_c_rdev_done;
+		if (best_c_rdev_done)
+			set_bit(best_c_rdev, &c_rdev_done);
 
 	} while (n_coupled > 1);
 
@@ -4706,8 +4713,60 @@ static int regulator_register_resolve_supply(struct device *dev, void *data)
 	return 0;
 }
 
+int regulator_coupler_register(struct regulator_coupler *coupler)
+{
+	mutex_lock(&regulator_list_mutex);
+	list_add_tail(&coupler->list, &regulator_coupler_list);
+	mutex_unlock(&regulator_list_mutex);
+
+	return 0;
+}
+
+static struct regulator_coupler *
+regulator_find_coupler(struct regulator_dev *rdev)
+{
+	struct regulator_coupler *coupler;
+	int err;
+
+	/*
+	 * Note that regulators are appended to the list and the generic
+	 * coupler is registered first, hence it will be attached at last
+	 * if nobody cared.
+	 */
+	list_for_each_entry_reverse(coupler, &regulator_coupler_list, list) {
+		err = coupler->attach_regulator(coupler, rdev);
+		if (!err) {
+			if (!coupler->balance_voltage &&
+			    rdev->coupling_desc.n_coupled > 2)
+				goto err_unsupported;
+
+			return coupler;
+		}
+
+		if (err < 0)
+			return ERR_PTR(err);
+
+		if (err == 1)
+			continue;
+
+		break;
+	}
+
+	return ERR_PTR(-EINVAL);
+
+err_unsupported:
+	if (coupler->detach_regulator)
+		coupler->detach_regulator(coupler, rdev);
+
+	rdev_err(rdev,
+		"Voltage balancing for multiple regulator couples is unimplemented\n");
+
+	return ERR_PTR(-EPERM);
+}
+
 static void regulator_resolve_coupling(struct regulator_dev *rdev)
 {
+	struct regulator_coupler *coupler = rdev->coupling_desc.coupler;
 	struct coupling_desc *c_desc = &rdev->coupling_desc;
 	int n_coupled = c_desc->n_coupled;
 	struct regulator_dev *c_rdev;
@@ -4723,6 +4782,12 @@ static void regulator_resolve_coupling(struct regulator_dev *rdev)
 		if (!c_rdev)
 			continue;
 
+		if (c_rdev->coupling_desc.coupler != coupler) {
+			rdev_err(rdev, "coupler mismatch with %s\n",
+				 rdev_get_name(c_rdev));
+			return;
+		}
+
 		regulator_lock(c_rdev);
 
 		c_desc->coupled_rdevs[i] = c_rdev;
@@ -4736,10 +4801,12 @@ static void regulator_resolve_coupling(struct regulator_dev *rdev)
 
 static void regulator_remove_coupling(struct regulator_dev *rdev)
 {
+	struct regulator_coupler *coupler = rdev->coupling_desc.coupler;
 	struct coupling_desc *__c_desc, *c_desc = &rdev->coupling_desc;
 	struct regulator_dev *__c_rdev, *c_rdev;
 	unsigned int __n_coupled, n_coupled;
 	int i, k;
+	int err;
 
 	n_coupled = c_desc->n_coupled;
 
@@ -4769,21 +4836,33 @@ static void regulator_remove_coupling(struct regulator_dev *rdev)
 		c_desc->coupled_rdevs[i] = NULL;
 		c_desc->n_resolved--;
 	}
+
+	if (coupler && coupler->detach_regulator) {
+		err = coupler->detach_regulator(coupler, rdev);
+		if (err)
+			rdev_err(rdev, "failed to detach from coupler: %d\n",
+				 err);
+	}
+
+	kfree(rdev->coupling_desc.coupled_rdevs);
+	rdev->coupling_desc.coupled_rdevs = NULL;
 }
 
 static int regulator_init_coupling(struct regulator_dev *rdev)
 {
-	int n_phandles;
+	int err, n_phandles;
+	size_t alloc_size;
 
 	if (!IS_ENABLED(CONFIG_OF))
 		n_phandles = 0;
 	else
 		n_phandles = of_get_n_coupled(rdev);
 
-	if (n_phandles + 1 > MAX_COUPLED) {
-		rdev_err(rdev, "too many regulators coupled\n");
-		return -EPERM;
-	}
+	alloc_size = sizeof(*rdev) * (n_phandles + 1);
+
+	rdev->coupling_desc.coupled_rdevs = kzalloc(alloc_size, GFP_KERNEL);
+	if (!rdev->coupling_desc.coupled_rdevs)
+		return -ENOMEM;
 
 	/*
 	 * Every regulator should always have coupling descriptor filled with
@@ -4797,23 +4876,35 @@ static int regulator_init_coupling(struct regulator_dev *rdev)
 	if (n_phandles == 0)
 		return 0;
 
-	/* regulator, which can't change its voltage, can't be coupled */
-	if (!regulator_ops_is_valid(rdev, REGULATOR_CHANGE_VOLTAGE)) {
-		rdev_err(rdev, "voltage operation not allowed\n");
+	if (!of_check_coupling_data(rdev))
 		return -EPERM;
-	}
 
-	if (rdev->constraints->max_spread <= 0) {
-		rdev_err(rdev, "wrong max_spread value\n");
-		return -EPERM;
+	rdev->coupling_desc.coupler = regulator_find_coupler(rdev);
+	if (IS_ERR(rdev->coupling_desc.coupler)) {
+		err = PTR_ERR(rdev->coupling_desc.coupler);
+		rdev_err(rdev, "failed to get coupler: %d\n", err);
+		return err;
 	}
 
-	if (!of_check_coupling_data(rdev))
+	return 0;
+}
+
+static int generic_coupler_attach(struct regulator_coupler *coupler,
+				  struct regulator_dev *rdev)
+{
+	if (rdev->coupling_desc.n_coupled > 2) {
+		rdev_err(rdev,
+			 "Voltage balancing for multiple regulator couples is unimplemented\n");
 		return -EPERM;
+	}
 
 	return 0;
 }
 
+static struct regulator_coupler generic_regulator_coupler = {
+	.attach_regulator = generic_coupler_attach,
+};
+
 /**
  * regulator_register - register regulator
  * @regulator_desc: regulator to register
@@ -4975,7 +5066,9 @@ regulator_register(const struct regulator_desc *regulator_desc,
 	if (ret < 0)
 		goto wash;
 
+	mutex_lock(&regulator_list_mutex);
 	ret = regulator_init_coupling(rdev);
+	mutex_unlock(&regulator_list_mutex);
 	if (ret < 0)
 		goto wash;
 
@@ -5024,6 +5117,7 @@ regulator_register(const struct regulator_desc *regulator_desc,
 unset_supplies:
 	mutex_lock(&regulator_list_mutex);
 	unset_regulator_supplies(rdev);
+	regulator_remove_coupling(rdev);
 	mutex_unlock(&regulator_list_mutex);
 wash:
 	kfree(rdev->constraints);
@@ -5479,6 +5573,8 @@ static int __init regulator_init(void)
 #endif
 	regulator_dummy_init();
 
+	regulator_coupler_register(&generic_regulator_coupler);
+
 	return ret;
 }
 
diff --git a/drivers/regulator/of_regulator.c b/drivers/regulator/of_regulator.c
index 0ead1164e4d6..397918ebba55 100644
--- a/drivers/regulator/of_regulator.c
+++ b/drivers/regulator/of_regulator.c
@@ -21,7 +21,8 @@ static const char *const regulator_states[PM_SUSPEND_MAX + 1] = {
 	[PM_SUSPEND_MAX]	= "regulator-state-disk",
 };
 
-static void of_get_regulation_constraints(struct device_node *np,
+static int of_get_regulation_constraints(struct device *dev,
+					struct device_node *np,
 					struct regulator_init_data **init_data,
 					const struct regulator_desc *desc)
 {
@@ -30,8 +31,13 @@ static void of_get_regulation_constraints(struct device_node *np,
 	struct device_node *suspend_np;
 	unsigned int mode;
 	int ret, i, len;
+	int n_phandles;
 	u32 pval;
 
+	n_phandles = of_count_phandle_with_args(np, "regulator-coupled-with",
+						NULL);
+	n_phandles = max(n_phandles, 0);
+
 	constraints->name = of_get_property(np, "regulator-name", NULL);
 
 	if (!of_property_read_u32(np, "regulator-min-microvolt", &pval))
@@ -163,9 +169,17 @@ 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;
+	if (n_phandles) {
+		constraints->max_spread = devm_kzalloc(dev,
+				sizeof(*constraints->max_spread) * n_phandles,
+				GFP_KERNEL);
+
+		if (!constraints->max_spread)
+			return -ENOMEM;
+
+		of_property_read_u32_array(np, "regulator-coupled-max-spread",
+					   constraints->max_spread, n_phandles);
+	}
 
 	if (!of_property_read_u32(np, "regulator-max-step-microvolt",
 				  &pval))
@@ -242,6 +256,8 @@ static void of_get_regulation_constraints(struct device_node *np,
 		suspend_state = NULL;
 		suspend_np = NULL;
 	}
+
+	return 0;
 }
 
 /**
@@ -267,7 +283,9 @@ struct regulator_init_data *of_get_regulator_init_data(struct device *dev,
 	if (!init_data)
 		return NULL; /* Out of memory? */
 
-	of_get_regulation_constraints(node, &init_data, desc);
+	if (of_get_regulation_constraints(dev, node, &init_data, desc))
+		return NULL;
+
 	return init_data;
 }
 EXPORT_SYMBOL_GPL(of_get_regulator_init_data);
@@ -473,7 +491,8 @@ int of_get_n_coupled(struct regulator_dev *rdev)
 
 /* 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)
+				  struct device_node *to_find,
+				  int *index)
 {
 	int n_phandles, i;
 	bool found = false;
@@ -495,8 +514,10 @@ static bool of_coupling_find_node(struct device_node *src,
 
 		of_node_put(tmp);
 
-		if (found)
+		if (found) {
+			*index = i;
 			break;
+		}
 	}
 
 	return found;
@@ -517,22 +538,23 @@ static bool of_coupling_find_node(struct device_node *src,
  */
 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 index;
 	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 max_spread = rdev->constraints->max_spread[i];
 		int c_max_spread, c_n_phandles;
 
+		if (max_spread <= 0) {
+			dev_err(&rdev->dev, "max_spread value invalid\n");
+			return false;
+		}
+
 		c_node = of_parse_phandle(node,
 					  "regulator-coupled-with", i);
 
@@ -549,22 +571,23 @@ bool of_check_coupling_data(struct regulator_dev *rdev)
 			goto clean;
 		}
 
-		if (of_property_read_u32(c_node, "regulator-coupled-max-spread",
-					 &c_max_spread)) {
+		if (!of_coupling_find_node(c_node, node, &index)) {
+			dev_err(&rdev->dev, "missing 2-way linking for coupled regulators\n");
 			ret = false;
 			goto clean;
 		}
 
-		if (c_max_spread != max_spread) {
-			dev_err(&rdev->dev,
-				"coupled regulators max_spread mismatch\n");
+		if (of_property_read_u32_index(c_node, "regulator-coupled-max-spread",
+					       index, &c_max_spread)) {
 			ret = false;
 			goto clean;
 		}
 
-		if (!of_coupling_find_node(c_node, node)) {
-			dev_err(&rdev->dev, "missing 2-way linking for coupled regulators\n");
+		if (c_max_spread != max_spread) {
+			dev_err(&rdev->dev,
+				"coupled regulators max_spread mismatch\n");
 			ret = false;
+			goto clean;
 		}
 
 clean:
diff --git a/include/linux/regulator/coupler.h b/include/linux/regulator/coupler.h
new file mode 100644
index 000000000000..98dd1f74d605
--- /dev/null
+++ b/include/linux/regulator/coupler.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * coupler.h -- SoC Regulator support, coupler API.
+ *
+ * Regulator Coupler Interface.
+ */
+
+#ifndef __LINUX_REGULATOR_COUPLER_H_
+#define __LINUX_REGULATOR_COUPLER_H_
+
+#include <linux/kernel.h>
+#include <linux/suspend.h>
+
+struct regulator_coupler;
+struct regulator_dev;
+
+/**
+ * struct regulator_coupler - customized regulator's coupler
+ *
+ * Regulator's coupler allows to customize coupling algorithm.
+ *
+ * @list: couplers list entry
+ * @attach_regulator: Callback invoked on creation of a coupled regulator,
+ *                    couples are unresolved at this point. The callee should
+ *                    check that it could handle the regulator and return 0 on
+ *                    success, -errno on failure and 1 if given regulator is
+ *                    not suitable for this coupler (case of having multiple
+ *                    regulators in a system). Callback shall be implemented.
+ * @detach_regulator: Callback invoked on destruction of a coupled regulator.
+ *                    This callback is optional and could be NULL.
+ * @balance_voltage: Callback invoked when voltage of a coupled regulator is
+ *                   changing. Called with all of the coupled rdev's being held
+ *                   under "consumer lock". The callee should perform voltage
+ *                   balancing, changing voltage of the coupled regulators as
+ *                   needed. It's up to the coupler to verify the voltage
+ *                   before changing it in hardware, i.e. coupler should
+ *                   check consumer's min/max and etc. This callback is
+ *                   optional and could be NULL, in which case a generic
+ *                   voltage balancer will be used.
+ */
+struct regulator_coupler {
+	struct list_head list;
+
+	int (*attach_regulator)(struct regulator_coupler *coupler,
+				struct regulator_dev *rdev);
+	int (*detach_regulator)(struct regulator_coupler *coupler,
+				struct regulator_dev *rdev);
+	int (*balance_voltage)(struct regulator_coupler *coupler,
+			       struct regulator_dev *rdev,
+			       suspend_state_t state);
+};
+
+#ifdef CONFIG_REGULATOR
+int regulator_coupler_register(struct regulator_coupler *coupler);
+#else
+static inline int regulator_coupler_register(struct regulator_coupler *coupler)
+{
+	return 0;
+}
+#endif
+
+#endif
diff --git a/include/linux/regulator/driver.h b/include/linux/regulator/driver.h
index 377da2357118..31b38a2b6995 100644
--- a/include/linux/regulator/driver.h
+++ b/include/linux/regulator/driver.h
@@ -15,8 +15,6 @@
 #ifndef __LINUX_REGULATOR_DRIVER_H_
 #define __LINUX_REGULATOR_DRIVER_H_
 
-#define MAX_COUPLED		2
-
 #include <linux/device.h>
 #include <linux/notifier.h>
 #include <linux/regulator/consumer.h>
@@ -426,7 +424,8 @@ struct regulator_config {
  * incremented.
  */
 struct coupling_desc {
-	struct regulator_dev *coupled_rdevs[MAX_COUPLED];
+	struct regulator_dev **coupled_rdevs;
+	struct regulator_coupler *coupler;
 	int n_resolved;
 	int n_coupled;
 };
@@ -552,4 +551,5 @@ void regulator_unlock(struct regulator_dev *rdev);
  */
 int regulator_desc_list_voltage_linear_range(const struct regulator_desc *desc,
 					     unsigned int selector);
+
 #endif
diff --git a/include/linux/regulator/machine.h b/include/linux/regulator/machine.h
index 1d34a70ffda2..21db06e5c1ed 100644
--- a/include/linux/regulator/machine.h
+++ b/include/linux/regulator/machine.h
@@ -156,7 +156,7 @@ struct regulation_constraints {
 	int system_load;
 
 	/* used for coupled regulators */
-	int max_spread;
+	u32 *max_spread;
 
 	/* used for changing voltage in steps */
 	int max_uV_step;
-- 
2.22.0