Date:	Thu,  7 Apr 2016 19:21:50 +0300
From:	Crestez Dan Leonard <leonard.crestez@...el.com>
To:	Jonathan Cameron <jic23@...nel.org>, linux-iio@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Hartmut Knaack <knaack.h@....de>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Peter Meerwald-Stadler <pmeerw@...erw.net>,
	Daniel Baluta <daniel.baluta@...el.com>,
	Crestez Dan Leonard <leonard.crestez@...el.com>
Subject: [PATCH 1/5] max44000: Initial commit

This just adds support for reporting illuminance with default settings.

All default registers are written on probe because the device otherwise
lacks a reset function.

Signed-off-by: Crestez Dan Leonard <leonard.crestez@...el.com>
---
 drivers/iio/light/Kconfig    |  11 ++
 drivers/iio/light/Makefile   |   1 +
 drivers/iio/light/max44000.c | 295 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 307 insertions(+)
 create mode 100644 drivers/iio/light/max44000.c

diff --git a/drivers/iio/light/Kconfig b/drivers/iio/light/Kconfig
index cfd3df8..42c15c1 100644
--- a/drivers/iio/light/Kconfig
+++ b/drivers/iio/light/Kconfig
@@ -320,4 +320,15 @@ config VCNL4000
 	 To compile this driver as a module, choose M here: the
 	 module will be called vcnl4000.
 
+config MAX44000
+	tristate "MAX44000 Ambient and Infrared Proximity Sensor"
+	depends on I2C
+	select REGMAP_I2C
+	help
+	 Say Y here if you want to build support for Maxim Integrated's
+	 MAX44000 ambient and infrared proximity sensor device.
+
+	 To compile this driver as a module, choose M here:
+	 the module will be called max44000.
+
 endmenu
diff --git a/drivers/iio/light/Makefile b/drivers/iio/light/Makefile
index b2c3105..14b2f36 100644
--- a/drivers/iio/light/Makefile
+++ b/drivers/iio/light/Makefile
@@ -30,3 +30,4 @@ obj-$(CONFIG_TCS3472)		+= tcs3472.o
 obj-$(CONFIG_TSL4531)		+= tsl4531.o
 obj-$(CONFIG_US5182D)		+= us5182d.o
 obj-$(CONFIG_VCNL4000)		+= vcnl4000.o
+obj-$(CONFIG_MAX44000)		+= max44000.o
diff --git a/drivers/iio/light/max44000.c b/drivers/iio/light/max44000.c
new file mode 100644
index 0000000..7c12153
--- /dev/null
+++ b/drivers/iio/light/max44000.c
@@ -0,0 +1,295 @@
+/*
+ * MAX44000 Ambient and Infrared Proximity Sensor
+ *
+ * Copyright (c) 2016, Intel Corporation.
+ *
+ * This file is subject to the terms and conditions of version 2 of
+ * the GNU General Public License.  See the file COPYING in the main
+ * directory of this archive for more details.
+ *
+ * Data sheet: https://datasheets.maximintegrated.com/en/ds/MAX44000.pdf
+ *
+ * 7-bit I2C slave address 0x4a
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/i2c.h>
+#include <linux/regmap.h>
+#include <linux/util_macros.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/acpi.h>
+
+#define MAX44000_DRV_NAME		"max44000"
+
+/* Registers in datasheet order */
+#define MAX44000_REG_STATUS		0x00
+#define MAX44000_REG_CFG_MAIN		0x01
+#define MAX44000_REG_CFG_RX		0x02
+#define MAX44000_REG_CFG_TX		0x03
+#define MAX44000_REG_ALS_DATA_HI	0x04
+#define MAX44000_REG_ALS_DATA_LO	0x05
+#define MAX44000_REG_PRX_DATA		0x16
+#define MAX44000_REG_ALS_UPTHR_HI	0x06
+#define MAX44000_REG_ALS_UPTHR_LO	0x07
+#define MAX44000_REG_ALS_LOTHR_HI	0x08
+#define MAX44000_REG_ALS_LOTHR_LO	0x09
+#define MAX44000_REG_PST		0x0a
+#define MAX44000_REG_PRX_IND		0x0b
+#define MAX44000_REG_PRX_THR		0x0c
+#define MAX44000_REG_TRIM_GAIN_GREEN	0x0f
+#define MAX44000_REG_TRIM_GAIN_IR	0x10
+
+#define MAX44000_ALSDATA_OVERFLOW	0x4000
+
+#define MAX44000_REGMASK_READABLE	0x419fff
+#define MAX44000_REGMASK_WRITEABLE	0x019fce
+#define MAX44000_REGMASK_VOLATILE	0x400031
+
+struct max44000_data {
+	struct mutex lock;
+	struct i2c_client *client;
+	struct regmap *regmap;
+};
+
+/* Default scale is set to the minimum of 0.03125 or 1 / (1 << 5) lux */
+#define MAX44000_ALS_TO_LUX_DEFAULT_FRACTION_LOG2 5
+
+static const struct iio_chan_spec max44000_channels[] = {
+	{
+		.type = IIO_LIGHT,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
+	},
+};
+
+static inline int max44000_read_alsval(struct max44000_data *data)
+{
+	u16 regval;
+	int ret;
+
+	regval = 0;
+	ret = regmap_bulk_read(data->regmap, MAX44000_REG_ALS_DATA_HI, &regval, 2);
+	if (ret < 0)
+		return ret;
+
+	regval = be16_to_cpu(regval);
+
+	/* Overflow is explained on datasheet page 17.
+	 *
+	 * It's a warning that either the G or IR channel has become saturated
+	 * and that the value in the register is likely incorrect.
+	 *
+	 * The recommendation is to change the scale (ALSPGA).
+	 * The driver just returns the max representable value.
+	 */
+	if (regval & MAX44000_ALSDATA_OVERFLOW)
+		return 0x3FFF;
+
+	return regval;
+}
+
+static int max44000_read_raw(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     int *val, int *val2, long mask)
+{
+	struct max44000_data *data = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		switch (chan->type) {
+		case IIO_LIGHT:
+			mutex_lock(&data->lock);
+			ret = max44000_read_alsval(data);
+			mutex_unlock(&data->lock);
+			if (ret < 0)
+				return ret;
+			*val = ret;
+			return IIO_VAL_INT;
+
+		default:
+			return -EINVAL;
+		}
+
+	case IIO_CHAN_INFO_SCALE:
+		switch (chan->type) {
+		case IIO_LIGHT:
+			*val = 1;
+			*val2 = MAX44000_ALS_TO_LUX_DEFAULT_FRACTION_LOG2;
+			return IIO_VAL_FRACTIONAL_LOG2;
+
+		default:
+			return -EINVAL;
+		}
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info max44000_info = {
+	.driver_module		= THIS_MODULE,
+	.read_raw		= max44000_read_raw,
+};
+
+static bool max44000_readable_reg(struct device *dev, unsigned int reg)
+{
+	return (1 << reg) & MAX44000_REGMASK_READABLE;
+}
+
+static bool max44000_writeable_reg(struct device *dev, unsigned int reg)
+{
+	return (1 << reg) & MAX44000_REGMASK_WRITEABLE;
+}
+
+static bool max44000_volatile_reg(struct device *dev, unsigned int reg)
+{
+	return (1 << reg) & MAX44000_REGMASK_VOLATILE;
+}
+
+static bool max44000_precious_reg(struct device *dev, unsigned int reg)
+{
+	return reg == MAX44000_REG_STATUS;
+}
+
+/* Datasheet pages 9-10: */
+static const struct reg_default max44000_reg_defaults[] = {
+	{ MAX44000_REG_CFG_MAIN,	0x24 },
+	/* Upper 4 bits are not documented but start as 1 on powerup
+	 * Setting them to 0 causes proximity to misbehave so set them to 1
+	 */
+	{ MAX44000_REG_CFG_RX,		0xf0 },
+	{ MAX44000_REG_CFG_TX,		0x00 },
+	{ MAX44000_REG_ALS_UPTHR_HI,	0x00 },
+	{ MAX44000_REG_ALS_UPTHR_LO,	0x00 },
+	{ MAX44000_REG_ALS_LOTHR_HI,	0x00 },
+	{ MAX44000_REG_ALS_LOTHR_LO,	0x00 },
+	{ MAX44000_REG_PST,		0x00 },
+	{ MAX44000_REG_PRX_IND,		0x00 },
+	{ MAX44000_REG_PRX_THR,		0x00 },
+	{ MAX44000_REG_TRIM_GAIN_GREEN,	0x80 },
+	{ MAX44000_REG_TRIM_GAIN_IR,	0x80 },
+};
+
+static const struct regmap_config max44000_regmap_config = {
+	.reg_bits	= 8,
+	.val_bits	= 8,
+
+	.max_register	= MAX44000_REG_PRX_DATA,
+	.readable_reg	= max44000_readable_reg,
+	.writeable_reg	= max44000_writeable_reg,
+	.volatile_reg	= max44000_volatile_reg,
+	.precious_reg	= max44000_precious_reg,
+
+	.use_single_rw	= 1,
+	.cache_type	= REGCACHE_FLAT,
+
+	.reg_defaults		= max44000_reg_defaults,
+	.num_reg_defaults	= ARRAY_SIZE(max44000_reg_defaults),
+};
+
+static int max44000_force_write_defaults(struct max44000_data *data)
+{
+	int i, ret;
+
+	for (i = 0; i < ARRAY_SIZE(max44000_reg_defaults); ++i) {
+		ret = regmap_write(data->regmap,
+				   max44000_reg_defaults[i].reg,
+				   max44000_reg_defaults[i].def);
+		if (ret)
+			return ret;
+	}
+	return 0;
+}
+
+static int max44000_probe(struct i2c_client *client,
+			  const struct i2c_device_id *id)
+{
+	struct max44000_data *data;
+	struct iio_dev *indio_dev;
+	int ret, reg;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+	data = iio_priv(indio_dev);
+	data->regmap = devm_regmap_init_i2c(client, &max44000_regmap_config);
+	if (IS_ERR(data->regmap)) {
+		dev_err(&client->dev, "regmap_init failed!\n");
+		return PTR_ERR(data->regmap);
+	}
+
+	i2c_set_clientdata(client, indio_dev);
+	data->client = client;
+	mutex_init(&data->lock);
+	indio_dev->dev.parent = &client->dev;
+	indio_dev->info = &max44000_info;
+	indio_dev->name = MAX44000_DRV_NAME;
+	indio_dev->channels = max44000_channels;
+	indio_dev->num_channels = ARRAY_SIZE(max44000_channels);
+
+	/* Read status at least once to clear the power-on-reset bit. */
+	ret = regmap_read(data->regmap, MAX44000_REG_STATUS, &reg);
+	if (ret < 0) {
+		dev_err(&data->client->dev, "failed to read init status: %d\n", ret);
+		return ret;
+	}
+
+	/* The device has no reset command, write defaults explicitly. */
+	ret = max44000_force_write_defaults(data);
+	if (ret < 0) {
+		dev_err(&data->client->dev, "failed to write defaults: %d\n", ret);
+		return ret;
+	}
+
+	return iio_device_register(indio_dev);
+}
+
+static int max44000_remove(struct i2c_client *client)
+{
+	struct iio_dev *indio_dev = i2c_get_clientdata(client);
+
+	iio_device_unregister(indio_dev);
+	return 0;
+}
+
+static const struct i2c_device_id max44000_id[] = {
+	{"max44000", 0},
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max44000_id);
+
+#ifdef CONFIG_OF
+static const struct of_device_id max44000_of_match[] = {
+	{ .compatible = "maxim,max44000" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max44000_of_match);
+#endif
+
+#ifdef CONFIG_ACPI
+static const struct acpi_device_id max44000_acpi_match[] = {
+	{"MAX44000", 0},
+	{ }
+};
+MODULE_DEVICE_TABLE(acpi, max44000_acpi_match);
+#endif
+
+static struct i2c_driver max44000_driver = {
+	.driver = {
+		.name	= MAX44000_DRV_NAME,
+		.of_match_table = of_match_ptr(max44000_of_match),
+		.acpi_match_table = ACPI_PTR(max44000_acpi_match),
+	},
+	.probe		= max44000_probe,
+	.remove		= max44000_remove,
+	.id_table	= max44000_id,
+};
+
+module_i2c_driver(max44000_driver);
+
+MODULE_AUTHOR("Crestez Dan Leonard <leonard.crestez@...el.com>");
+MODULE_DESCRIPTION("MAX44000 Ambient and Infrared Proximity Sensor");
+MODULE_LICENSE("GPL v2");
-- 
2.8.0.rc3

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