From 4511db2505322c2fbbcd082399bd65f98a4d187e Mon Sep 17 00:00:00 2001
From: Etienne Carriere <etienne.carriere@foss.st.com>
Date: Mon, 2 Oct 2023 09:39:04 +0200
Subject: [PATCH] drivers: regulator: always on property

Implements always-on regulator property for regulators that once enabled
shall never be disabled. This is archived using a regulator_enable()
call to increment its refcount.

Signed-off-by: Etienne Carriere <etienne.carriere@foss.st.com>
---
 core/drivers/regulator/regulator.c | 22 ++++++++++++++++++----
 core/include/drivers/regulator.h   | 23 +++++++++++++++++++++++
 2 files changed, 41 insertions(+), 4 deletions(-)

diff --git a/core/drivers/regulator/regulator.c b/core/drivers/regulator/regulator.c
index 1ece3b51f06..334d804be76 100644
--- a/core/drivers/regulator/regulator.c
+++ b/core/drivers/regulator/regulator.c
@@ -108,6 +108,9 @@ TEE_Result regulator_enable(struct regulator *regulator)
 	assert(regulator);
 	FMSG("%s", regulator_name(regulator));
 
+	if (regulator_is_always_on(regulator))
+		return TEE_SUCCESS;
+
 	return regulator_refcnt_enable(regulator);
 }
 
@@ -153,6 +156,9 @@ TEE_Result regulator_disable(struct regulator *regulator)
 	assert(regulator);
 	FMSG("%s", regulator_name(regulator));
 
+	if (regulator_is_always_on(regulator))
+		return TEE_SUCCESS;
+
 	return regulator_refcnt_disable(regulator);
 }
 
@@ -213,7 +219,8 @@ TEE_Result regulator_register(struct regulator *regulator)
 	int max_uv = 0;
 	int uv = 0;
 
-	if (!regulator || !regulator->ops)
+	if (!regulator || !regulator->ops ||
+	    regulator->flags & ~REGULATOR_FLAGS_MASK)
 		return TEE_ERROR_BAD_PARAMETERS;
 
 	regulator_get_range(regulator, &min_uv, &max_uv);
@@ -236,6 +243,13 @@ TEE_Result regulator_register(struct regulator *regulator)
 			return res;
 	}
 
+	/* Unbalanced enable refcount to keep always-on regulators enabled */
+	if (regulator_is_always_on(regulator)) {
+		res = regulator_refcnt_enable(regulator);
+		if (res)
+			return res;
+	}
+
 	SLIST_INSERT_HEAD(&regulator_device_list, regulator, link);
 
 	return TEE_SUCCESS;
@@ -249,14 +263,14 @@ void regulator_print_state(const char *message __maybe_unused)
 	struct regulator *regulator = NULL;
 
 	DMSG("Regulator state: %s", message);
-	DMSG("name     use\ten\tuV\tmin\tmax\tsupply");
+	DMSG("name     use\ten\tuV\tmin\tmax\tflags\tsupply");
 
 	SLIST_FOREACH(regulator, &regulator_device_list, link)
-		DMSG("%8s %u\t%d\t%d\t%d\t%d\t%s\n",
+		DMSG("%8s %u\t%d\t%d\t%d\t%d\t%#x\t%s\n",
 		     regulator->name, regulator->refcount,
 		     regulator_is_enabled(regulator),
 		     regulator_get_voltage(regulator),
-		     regulator->min_uv, regulator->max_uv,
+		     regulator->min_uv, regulator->max_uv, regulator->flags,
 		     regulator->supply ? regulator_name(regulator->supply) :
 		     "<none>");
 }
diff --git a/core/include/drivers/regulator.h b/core/include/drivers/regulator.h
index ed1570d4d6b..feb1fe3fe7b 100644
--- a/core/include/drivers/regulator.h
+++ b/core/include/drivers/regulator.h
@@ -12,6 +12,18 @@
 #include <tee_api_types.h>
 #include <stdbool.h>
 #include <stdint.h>
+#include <util.h>
+
+/*
+ * Regulator property flags: related to device tree binding properties
+ *
+ * REGUL_ALWAYS_ON
+ * Regulator should never be disabled. Relates to device tree binding
+ * property regulator-always-on.
+ */
+#define REGULATOR_ALWAYS_ON	BIT(0)
+
+#define REGULATOR_FLAGS_MASK	REGULATOR_ALWAYS_ON
 
 struct regulator_ops;
 
@@ -24,6 +36,7 @@ struct regulator_ops;
  * @min_uv: Min possible voltage level in microvolt (uV)
  * @max_uv: Max possible voltage level in microvolt (uV)
  * @cur_uv: Current voltage level in microvolt (uV)
+ * @flags: REGULATOR_* property flags
  * @refcount: Regulator enable request reference counter
  * @lock: Mutex for concurrent access protection
  * @link: Link in initialized regulator list
@@ -38,6 +51,7 @@ struct regulator {
 	int max_uv;
 	/* Fields internal to regulator framework */
 	int cur_uv;
+	unsigned int flags;
 	unsigned int refcount;
 	struct mutex lock;	/* Concurrent access protection */
 	SLIST_ENTRY(regulator) link;
@@ -134,6 +148,15 @@ static inline const char *regulator_name(struct regulator *regulator)
 	return regulator->name;
 }
 
+/*
+ * regulator_is_always_on() - Return the state of REGULATOR_ALWAYS_ON flag
+ * @regulator: Regulator reference
+ */
+static inline bool regulator_is_always_on(struct regulator *regulator)
+{
+	return regulator->flags & REGULATOR_ALWAYS_ON;
+}
+
 /*
  * regulator_set_min_voltage() - Set regulator to its min level
  * @regulator: Regulator reference