From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Qingshuang Fu <fuqingshuang@kylinos.cn>,
	Guenter Roeck <linux@roeck-us.net>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.6 061/156] hwmon: (ads7828) Fix external VREF regulator handling
Date: Mon, 17 Aug 2026 15:33:15 +0200
Message-ID: <20260817132536.977123035@linuxfoundation.org>
In-Reply-To: <20260817132534.666299318@linuxfoundation.org>
References: <20260817132534.666299318@linuxfoundation.org>
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6.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Qingshuang Fu <fuqingshuang@kylinos.cn>

[ Upstream commit fddb5ceaf901b050ed2a1a7deeecbf97e003435a ]

The driver currently has two issues with the external VREF regulator
handling in ads7828_probe():

1. All errors from devm_regulator_get_optional() are ignored, causing the
   driver to incorrectly fall back to internal VREF even for transient
   errors like -EPROBE_DEFER or genuine failures like -ENOMEM.

2. The external regulator is never enabled. The driver calls
   regulator_get_voltage() without first calling regulator_enable(),
   so the VREF pin may remain unpowered if the regulator is not
   configured as always-on.

Fix both issues by switching to devm_regulator_get_enable_read_voltage(),
which handles regulator get, enable, and voltage read in one call.
Only -ENODEV (no regulator specified in device tree) should trigger the
fallback to internal VREF. All other errors are propagated to the caller.

Fixes: a8ddfea09566 ("hwmon: (ads7828) Accept optional parameters from device tree")
Signed-off-by: Qingshuang Fu <fuqingshuang@kylinos.cn>
Link: https://lore.kernel.org/r/20260805061645.1331652-1-fffsqian@163.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/hwmon/ads7828.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/hwmon/ads7828.c b/drivers/hwmon/ads7828.c
index 809e830f52a6b..b9ed146a24cc1 100644
--- a/drivers/hwmon/ads7828.c
+++ b/drivers/hwmon/ads7828.c
@@ -108,12 +108,11 @@ static int ads7828_probe(struct i2c_client *client)
 	struct ads7828_data *data;
 	struct device *hwmon_dev;
 	unsigned int vref_mv = ADS7828_INT_VREF_MV;
-	unsigned int vref_uv;
+	int vref_uv;
 	bool diff_input = false;
 	bool ext_vref = false;
 	unsigned int regval;
 	enum ads7828_chips chip;
-	struct regulator *reg;
 
 	data = devm_kzalloc(dev, sizeof(struct ads7828_data), GFP_KERNEL);
 	if (!data)
@@ -127,9 +126,11 @@ static int ads7828_probe(struct i2c_client *client)
 	} else if (dev->of_node) {
 		diff_input = of_property_read_bool(dev->of_node,
 						   "ti,differential-input");
-		reg = devm_regulator_get_optional(dev, "vref");
-		if (!IS_ERR(reg)) {
-			vref_uv = regulator_get_voltage(reg);
+		vref_uv = devm_regulator_get_enable_read_voltage(dev, "vref");
+		if (vref_uv < 0) {
+			if (vref_uv != -ENODEV)
+				return vref_uv;
+		} else {
 			vref_mv = DIV_ROUND_CLOSEST(vref_uv, 1000);
 			if (vref_mv < ADS7828_EXT_VREF_MV_MIN ||
 			    vref_mv > ADS7828_EXT_VREF_MV_MAX)
-- 
2.53.0