linux-kernel - [PATCH v2 07/14] iio: accel: bma220: reset registers during init stage

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Message-Id: <20250910-bma220_improvements-v2-7-e23f4f2b9745@subdimension.ro>
Date: Wed, 10 Sep 2025 10:57:12 +0300
From: Petre Rodan <petre.rodan@...dimension.ro>
To: Jonathan Cameron <jic23@...nel.org>, 
 David Lechner <dlechner@...libre.com>, 
 Nuno Sá <nuno.sa@...log.com>, 
 Andy Shevchenko <andy@...nel.org>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>, 
 linux-iio@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Petre Rodan <petre.rodan@...dimension.ro>
Subject: [PATCH v2 07/14] iio: accel: bma220: reset registers during init
 stage

Bring all configuration registers to default values during device probe().

Signed-off-by: Petre Rodan <petre.rodan@...dimension.ro>
---
 drivers/iio/accel/bma220_core.c | 71 ++++++++++++++++++++++++++++-------------
 1 file changed, 49 insertions(+), 22 deletions(-)

diff --git a/drivers/iio/accel/bma220_core.c b/drivers/iio/accel/bma220_core.c
index b6f1374a9cca52966c1055113710061a7284cf5a..322df516c90a7c645eeca579cae9803eb31caad1 100644
--- a/drivers/iio/accel/bma220_core.c
+++ b/drivers/iio/accel/bma220_core.c
@@ -29,12 +29,15 @@
 #define BMA220_REG_ACCEL_Z			0x04
 #define BMA220_REG_RANGE			0x11
 #define BMA220_REG_SUSPEND			0x18
+#define BMA220_REG_SOFTRESET			0x19
 
 #define BMA220_CHIP_ID				0xDD
 #define BMA220_READ_MASK			BIT(7)
 #define BMA220_RANGE_MASK			GENMASK(1, 0)
 #define BMA220_SUSPEND_SLEEP			0xFF
 #define BMA220_SUSPEND_WAKE			0x00
+#define BMA220_RESET_MODE			0xFF
+#define BMA220_NONRESET_MODE			0x00
 
 #define BMA220_DEVICE_NAME			"bma220"
 
@@ -203,31 +206,28 @@ static const struct iio_info bma220_info = {
 	.read_avail		= bma220_read_avail,
 };
 
-static int bma220_init(struct spi_device *spi)
+static int bma220_reset(struct spi_device *spi, bool up)
 {
-	int ret;
-	static const char * const regulator_names[] = { "vddd", "vddio", "vdda" };
+	int i, ret;
 
-	ret = devm_regulator_bulk_get_enable(&spi->dev,
-					     ARRAY_SIZE(regulator_names),
-					     regulator_names);
-	if (ret)
-		return dev_err_probe(&spi->dev, ret, "Failed to get regulators\n");
+	/**
+	 * The chip can be reset by a simple register read.
+	 * We need up to 2 register reads of the softreset register
+	 * to make sure that the device is in the desired state.
+	 */
+	for (i = 0; i < 2; i++) {
+		ret = bma220_read_reg(spi, BMA220_REG_SOFTRESET);
+		if (ret < 0)
+			return ret;
 
-	ret = bma220_read_reg(spi, BMA220_REG_ID);
-	if (ret != BMA220_CHIP_ID)
-		return -ENODEV;
+		if (up && (ret == BMA220_RESET_MODE))
+			return 0;
 
-	/* Make sure the chip is powered on */
-	ret = bma220_read_reg(spi, BMA220_REG_SUSPEND);
-	if (ret == BMA220_SUSPEND_WAKE)
-		ret = bma220_read_reg(spi, BMA220_REG_SUSPEND);
-	if (ret < 0)
-		return ret;
-	if (ret == BMA220_SUSPEND_WAKE)
-		return -EBUSY;
+		if (!up && (ret == BMA220_NONRESET_MODE))
+			return 0;
+	}
 
-	return 0;
+	return -EBUSY;
 }
 
 static int bma220_power(struct spi_device *spi, bool up)
@@ -244,16 +244,43 @@ static int bma220_power(struct spi_device *spi, bool up)
 		if (ret < 0)
 			return ret;
 
-		if (up && ret == BMA220_SUSPEND_SLEEP)
+		if (up && (ret == BMA220_SUSPEND_SLEEP))
 			return 0;
 
-		if (!up && ret == BMA220_SUSPEND_WAKE)
+		if (!up && (ret == BMA220_SUSPEND_WAKE))
 			return 0;
 	}
 
 	return -EBUSY;
 }
 
+static int bma220_init(struct spi_device *spi)
+{
+	int ret;
+	static const char * const regulator_names[] = { "vddd", "vddio", "vdda" };
+
+	ret = devm_regulator_bulk_get_enable(&spi->dev,
+					     ARRAY_SIZE(regulator_names),
+					     regulator_names);
+	if (ret)
+		return dev_err_probe(&spi->dev, ret, "Failed to get regulators\n");
+
+	ret = bma220_read_reg(spi, BMA220_REG_ID);
+	if (ret != BMA220_CHIP_ID)
+		return -ENODEV;
+
+	/* Make sure the chip is powered on and config registers are reset */
+	ret = bma220_power(spi, true);
+	if (ret)
+		return dev_err_probe(&spi->dev, ret, "Failed to power-on chip\n");
+
+	ret = bma220_reset(spi, true);
+	if (ret)
+		return dev_err_probe(&spi->dev, ret, "Failed to soft reset chip\n");
+
+	return 0;
+}
+
 static void bma220_deinit(void *spi)
 {
 	bma220_power(spi, false);

-- 
2.49.1