regulator: core: Introduce API for regulators coupling customization

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>
Signed-off-by: Mark Brown <broonie@kernel.org>

3 files changed, 66 insertions, 4 deletions

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;