linux-kernel - [PATCH 2/2] hwmon: (sy7636a) enable regulator only if needed

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Message-ID: <20250920114311.291450-3-andreas@kemnade.info>
Date: Sat, 20 Sep 2025 13:43:11 +0200
From: Andreas Kemnade <andreas@...nade.info>
To: jdelvare@...e.com,
	linux@...ck-us.net,
	lgirdwood@...il.com,
	broonie@...nel.org,
	linux-hwmon@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Alistair Francis <alistair@...stair23.me>
Cc: Andreas Kemnade <andreas@...nade.info>
Subject: [PATCH 2/2] hwmon: (sy7636a) enable regulator only if needed

Avoid having all the regulators in the SY7636A enabled all the time
to significantly reduce current consumption. In pratical scenarios,
the regulators are only needed when a refresh is done on the epaper
display powered by the SY7636A. This is can save around 10mA which
is much for this kind of devices.
Also fixes the asymmetrical single enable call.

Signed-off-by: Andreas Kemnade <andreas@...nade.info>
---
 drivers/hwmon/sy7636a-hwmon.c | 34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff --git a/drivers/hwmon/sy7636a-hwmon.c b/drivers/hwmon/sy7636a-hwmon.c
index e83d0e50c735..0fda69bea3b4 100644
--- a/drivers/hwmon/sy7636a-hwmon.c
+++ b/drivers/hwmon/sy7636a-hwmon.c
@@ -18,14 +18,26 @@
 
 #include <linux/mfd/sy7636a.h>
 
+struct sy7636a_hwmon_data {
+	struct regmap *regmap;
+	struct regulator *regulator;
+};
+
+
 static int sy7636a_read(struct device *dev, enum hwmon_sensor_types type,
 			u32 attr, int channel, long *temp)
 {
-	struct regmap *regmap = dev_get_drvdata(dev);
+	struct sy7636a_hwmon_data *drvdata = dev_get_drvdata(dev);
 	int ret, reg_val;
 
-	ret = regmap_read(regmap,
+	ret = regulator_enable(drvdata->regulator);
+	if (ret)
+		return ret;
+
+	ret = regmap_read(drvdata->regmap,
 			  SY7636A_REG_TERMISTOR_READOUT, &reg_val);
+	regulator_disable(drvdata->regulator);
+
 	if (ret)
 		return ret;
 
@@ -66,23 +78,24 @@ static const struct hwmon_chip_info sy7636a_chip_info = {
 static int sy7636a_sensor_probe(struct platform_device *pdev)
 {
 	struct regmap *regmap = dev_get_regmap(pdev->dev.parent, NULL);
-	struct regulator *regulator;
+	struct sy7636a_hwmon_data *drvdata;
 	struct device *hwmon_dev;
 	int err;
 
 	if (!regmap)
 		return -EPROBE_DEFER;
 
-	regulator = devm_regulator_get_optional(&pdev->dev, "vcom");
-	if (IS_ERR_OR_NULL(regulator))
-		return -EPROBE_DEFER;
+	drvdata = devm_kzalloc(&pdev->dev, sizeof(*drvdata), GFP_KERNEL);
+	if (!drvdata)
+		return -ENOMEM;
 
-	err = regulator_enable(regulator);
-	if (err)
-		return err;
+	drvdata->regmap = regmap;
+	drvdata->regulator = devm_regulator_get_optional(&pdev->dev, "vcom");
+	if (IS_ERR_OR_NULL(drvdata->regulator))
+		return -EPROBE_DEFER;
 
 	hwmon_dev = devm_hwmon_device_register_with_info(&pdev->dev,
-							 "sy7636a_temperature", regmap,
+							 "sy7636a_temperature", drvdata,
 							 &sy7636a_chip_info, NULL);
 
 	if (IS_ERR(hwmon_dev)) {
@@ -102,5 +115,6 @@ static struct platform_driver sy7636a_sensor_driver = {
 };
 module_platform_driver(sy7636a_sensor_driver);
 
+MODULE_ALIAS("platform:sy7636a-temperature");
 MODULE_DESCRIPTION("SY7636A sensor driver");
 MODULE_LICENSE("GPL");
-- 
2.47.3