[RFC 2/2] iio: accel: mxc4005: Reset chip on probe() and resume()

[Hans de Goede <hdegoede@redhat.com>]

On some designs the chip is not properly reset when powered up at boot or
after a suspend/resume cycle.

Use the sw-reset feature to ensure that the chip is in a clean state
after probe() / resume() and in the case of resume() restore the settings
(scale, trigger-enabled).

Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218578
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/iio/accel/mxc4005.c | 58 +++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)

diff --git a/drivers/iio/accel/mxc4005.c b/drivers/iio/accel/mxc4005.c
index 111f4bcf24ad..9f38d3a08299 100644
--- a/drivers/iio/accel/mxc4005.c
+++ b/drivers/iio/accel/mxc4005.c
@@ -5,6 +5,7 @@
  * Copyright (c) 2014, Intel Corporation.
  */
 
+#include <linux/delay.h>
 #include <linux/module.h>
 #include <linux/i2c.h>
 #include <linux/iio/iio.h>
@@ -36,6 +37,7 @@
 
 #define MXC4005_REG_INT_CLR1		0x01
 #define MXC4005_REG_INT_CLR1_BIT_DRDYC	0x01
+#define MXC4005_REG_INT_CLR1_SW_RST	0x10
 
 #define MXC4005_REG_CONTROL		0x0D
 #define MXC4005_REG_CONTROL_MASK_FSR	GENMASK(6, 5)
@@ -43,6 +45,9 @@
 
 #define MXC4005_REG_DEVICE_ID		0x0E
 
+/* Datasheet does not specify a reset time, this is a conservative guess */
+#define MXC4005_RESET_TIME_US		2000
+
 enum mxc4005_axis {
 	AXIS_X,
 	AXIS_Y,
@@ -66,6 +71,8 @@ struct mxc4005_data {
 		s64 timestamp __aligned(8);
 	} scan;
 	bool trigger_enabled;
+	unsigned int control;
+	unsigned int int_mask1;
 };
 
 /*
@@ -349,6 +356,7 @@ static int mxc4005_set_trigger_state(struct iio_trigger *trig,
 		return ret;
 	}
 
+	data->int_mask1 = val;
 	data->trigger_enabled = state;
 	mutex_unlock(&data->mutex);
 
@@ -384,6 +392,13 @@ static int mxc4005_chip_init(struct mxc4005_data *data)
 
 	dev_dbg(data->dev, "MXC4005 chip id %02x\n", reg);
 
+	ret = regmap_write(data->regmap, MXC4005_REG_INT_CLR1,
+			   MXC4005_REG_INT_CLR1_SW_RST);
+	if (ret < 0)
+		return dev_err_probe(data->dev, ret, "resetting chip\n");
+
+	fsleep(MXC4005_RESET_TIME_US);
+
 	ret = regmap_write(data->regmap, MXC4005_REG_INT_MASK0, 0);
 	if (ret < 0)
 		return dev_err_probe(data->dev, ret, "writing INT_MASK0\n");
@@ -479,6 +494,48 @@ static int mxc4005_probe(struct i2c_client *client)
 	return devm_iio_device_register(&client->dev, indio_dev);
 }
 
+static int mxc4005_suspend(struct device *dev)
+{
+	struct iio_dev *indio_dev = dev_get_drvdata(dev);
+	struct mxc4005_data *data = iio_priv(indio_dev);
+	int ret;
+
+	/* Save control to restore it on resume */
+	ret = regmap_read(data->regmap, MXC4005_REG_CONTROL, &data->control);
+	if (ret < 0)
+		dev_err(data->dev, "failed to read reg_control\n");
+
+	return ret;
+}
+
+static int mxc4005_resume(struct device *dev)
+{
+	struct iio_dev *indio_dev = dev_get_drvdata(dev);
+	struct mxc4005_data *data = iio_priv(indio_dev);
+	int ret;
+
+	ret = regmap_write(data->regmap, MXC4005_REG_INT_CLR1,
+			   MXC4005_REG_INT_CLR1_SW_RST);
+	if (ret) {
+		dev_err(data->dev, "failed to reset chip: %d\n", ret);
+		return ret;
+	}
+
+	fsleep(MXC4005_RESET_TIME_US);
+
+	ret = regmap_write(data->regmap, MXC4005_REG_CONTROL, data->control);
+	ret |= regmap_write(data->regmap, MXC4005_REG_INT_MASK0, 0);
+	ret |= regmap_write(data->regmap, MXC4005_REG_INT_MASK1, data->int_mask1);
+	if (ret) {
+		dev_err(data->dev, "failed to restore registers\n");
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(mxc4005_pm_ops, mxc4005_suspend, mxc4005_resume);
+
 static const struct acpi_device_id mxc4005_acpi_match[] = {
 	{"MXC4005",	0},
 	{"MXC6655",	0},
@@ -506,6 +563,7 @@ static struct i2c_driver mxc4005_driver = {
 		.name = MXC4005_DRV_NAME,
 		.acpi_match_table = mxc4005_acpi_match,
 		.of_match_table = mxc4005_of_match,
+		.pm = pm_sleep_ptr(&mxc4005_pm_ops),
 	},
 	.probe		= mxc4005_probe,
 	.id_table	= mxc4005_id,
-- 
2.44.0