[PATCH] regulator: core: Add option to prevent disabling unused regulators

[Javier Martinez Canillas <javierm@redhat.com>]

This may be useful for debugging and develompent purposes, when there are
drivers that depend on regulators to be enabled but do not request them.

It is inspired from the clk_ignore_unused and pd_ignore_unused parameters,
that are used to keep firmware-enabled clocks and power domains on even if
these are not used by drivers.

The parameter is not expected to be used in normal cases and should not be
needed on a platform with proper driver support.

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
---

 Documentation/admin-guide/kernel-parameters.txt |  7 +++++++
 drivers/regulator/core.c                        | 17 +++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 0a1731a0f0ef..91b58d767c2c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5461,6 +5461,13 @@
 			print every Nth verbose statement, where N is the value
 			specified.
 
+	regulator_ignore_unused
+			[REGULATOR]
+			Prevents the regulator framework to disable regulators
+			that are unused due not driver claiming them. This may
+			be useful for debug and development, but should not be
+			needed on a platform with proper driver support.
+
 	relax_domain_level=
 			[KNL, SMP] Set scheduler's default relax_domain_level.
 			See Documentation/admin-guide/cgroup-v1/cpusets.rst.
diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 3137e40fcd3e..220034ff0273 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -6234,6 +6234,14 @@ static int regulator_late_cleanup(struct device *dev, void *data)
 	return 0;
 }
 
+static bool regulator_ignore_unused;
+static int __init regulator_ignore_unused_setup(char *__unused)
+{
+	regulator_ignore_unused = true;
+	return 1;
+}
+__setup("regulator_ignore_unused", regulator_ignore_unused_setup);
+
 static void regulator_init_complete_work_function(struct work_struct *work)
 {
 	/*
@@ -6246,6 +6254,15 @@ static void regulator_init_complete_work_function(struct work_struct *work)
 	class_for_each_device(&regulator_class, NULL, NULL,
 			      regulator_register_resolve_supply);
 
+	/*
+	 * For debugging purposes, it may be useful to prevent unused
+	 * regulators to be disabled.
+	 */
+	if (regulator_ignore_unused) {
+		pr_warn("regulator: Not disabling unused regulators\n");
+		return;
+	}
+
 	/* If we have a full configuration then disable any regulators
 	 * we have permission to change the status for and which are
 	 * not in use or always_on.  This is effectively the default
-- 
2.41.0