Message-ID: <57135509.9020508@kernel.org>
Date:	Sun, 17 Apr 2016 10:19:05 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	Crestez Dan Leonard <leonard.crestez@...el.com>,
	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>,
	Mark Brown <broonie@...aro.org>
Subject: Re: [PATCH v2 1/5] max44000: Initial support

On 11/04/16 19:52, Crestez Dan Leonard wrote:
> This just adds support for reporting illuminance with default settings.
> 
> Important default registers are written on probe because the device
> otherwise lacks a reset function.
> 
> Signed-off-by: Crestez Dan Leonard <leonard.crestez@...el.com>
cc'ing Mark Brown for regcache flat discussion..   Mark I don't suppose you
have any docs anywhere I can point people at on this.  It comes round rather
to frequently for my taste and I can't immediately find any references in
the tree or code to explain what REGCACHE_FLAT is for...  I've cc'd your
previous email on the subject, but it's not really documentation.


> ---
>  drivers/iio/light/Kconfig    |  11 ++
>  drivers/iio/light/Makefile   |   1 +
>  drivers/iio/light/max44000.c | 336 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 348 insertions(+)
>  create mode 100644 drivers/iio/light/max44000.c
> 
> diff --git a/drivers/iio/light/Kconfig b/drivers/iio/light/Kconfig
> index cfd3df8..b4ab65b 100644
> --- a/drivers/iio/light/Kconfig
> +++ b/drivers/iio/light/Kconfig
> @@ -223,6 +223,17 @@ config LTR501
>  	 This driver can also be built as a module.  If so, the module
>           will be called ltr501.
>  
> +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.
> +
>  config OPT3001
>  	tristate "Texas Instruments OPT3001 Light Sensor"
>  	depends on I2C
> diff --git a/drivers/iio/light/Makefile b/drivers/iio/light/Makefile
> index b2c3105..c77f27f 100644
> --- a/drivers/iio/light/Makefile
> +++ b/drivers/iio/light/Makefile
> @@ -20,6 +20,7 @@ obj-$(CONFIG_ISL29125)		+= isl29125.o
>  obj-$(CONFIG_JSA1212)		+= jsa1212.o
>  obj-$(CONFIG_SENSORS_LM3533)	+= lm3533-als.o
>  obj-$(CONFIG_LTR501)		+= ltr501.o
> +obj-$(CONFIG_MAX44000)		+= max44000.o
>  obj-$(CONFIG_OPT3001)		+= opt3001.o
>  obj-$(CONFIG_PA12203001)	+= pa12203001.o
>  obj-$(CONFIG_RPR0521)		+= rpr0521.o
> diff --git a/drivers/iio/light/max44000.c b/drivers/iio/light/max44000.c
> new file mode 100644
> index 0000000..707cc24
> --- /dev/null
> +++ b/drivers/iio/light/max44000.c
> @@ -0,0 +1,336 @@
> +/*
> + * 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
> +
> +/* REG_CFG bits */
> +#define MAX44000_CFG_ALSINTE            0x01
> +#define MAX44000_CFG_PRXINTE            0x02
> +#define MAX44000_CFG_MASK               0x1c
> +#define MAX44000_CFG_MODE_SHUTDOWN      0x00
> +#define MAX44000_CFG_MODE_ALS_GIR       0x04
> +#define MAX44000_CFG_MODE_ALS_G         0x08
> +#define MAX44000_CFG_MODE_ALS_IR        0x0c
> +#define MAX44000_CFG_MODE_ALS_PRX       0x10
> +#define MAX44000_CFG_MODE_PRX           0x14
> +#define MAX44000_CFG_TRIM               0x20
> +
> +/*
> + * 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
> + */
> +#define MAX44000_REG_CFG_RX_DEFAULT 0xf0
> +
> +#define MAX44000_ALSDATA_OVERFLOW	0x4000
> +
> +#define MAX44000_REGMASK_READABLE ( \
Whilst an improvement I'd still prefer the nice clean
switch statement in the function.  Let the compiler do the magic for
you.
> +		(1 << MAX44000_REG_STATUS) | \
> +		(1 << MAX44000_REG_CFG_MAIN) | \
> +		(1 << MAX44000_REG_CFG_RX) | \
> +		(1 << MAX44000_REG_CFG_TX) | \
> +		(1 << MAX44000_REG_ALS_DATA_HI) | \
> +		(1 << MAX44000_REG_ALS_DATA_LO) | \
> +		(1 << MAX44000_REG_PRX_DATA) | \
> +		(1 << MAX44000_REG_ALS_UPTHR_HI) | \
> +		(1 << MAX44000_REG_ALS_UPTHR_LO) | \
> +		(1 << MAX44000_REG_ALS_LOTHR_HI) | \
> +		(1 << MAX44000_REG_ALS_LOTHR_LO) | \
> +		(1 << MAX44000_REG_PST) | \
> +		(1 << MAX44000_REG_PRX_IND) | \
> +		(1 << MAX44000_REG_PRX_THR) | \
> +		(1 << MAX44000_REG_TRIM_GAIN_GREEN) | \
> +		(1 << MAX44000_REG_TRIM_GAIN_IR))
> +
> +#define MAX44000_REGMASK_WRITEABLE ( \
> +		(1 << MAX44000_REG_CFG_MAIN) | \
> +		(1 << MAX44000_REG_CFG_RX) | \
> +		(1 << MAX44000_REG_CFG_TX) | \
> +		(1 << MAX44000_REG_ALS_UPTHR_HI) | \
> +		(1 << MAX44000_REG_ALS_UPTHR_LO) | \
> +		(1 << MAX44000_REG_ALS_LOTHR_HI) | \
> +		(1 << MAX44000_REG_ALS_LOTHR_LO) | \
> +		(1 << MAX44000_REG_PST) | \
> +		(1 << MAX44000_REG_PRX_IND) | \
> +		(1 << MAX44000_REG_PRX_THR) | \
> +		(1 << MAX44000_REG_TRIM_GAIN_GREEN) | \
> +		(1 << MAX44000_REG_TRIM_GAIN_IR))
> +
> +#define MAX44000_REGMASK_VOLATILE ( \
> +		(1 << MAX44000_REG_STATUS) | \
> +		(1 << MAX44000_REG_ALS_DATA_HI) | \
> +		(1 << MAX44000_REG_ALS_DATA_LO) | \
> +		(1 << MAX44000_REG_PRX_DATA))
> +
> +struct max44000_data {
> +	struct mutex lock;
> +	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 int max44000_read_alsval(struct max44000_data *data)
> +{
> +	u16 regval;
> +	int ret;
> +
> +	ret = regmap_bulk_read(data->regmap, MAX44000_REG_ALS_DATA_HI,
> +			       &regval, sizeof(regval));
> +	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.
> +	 */
Good comment. Thanks for adding it.
> +	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;
On this one I'm not sure the define adds anything given it really is a
numerical value.. I'd just put it inline here.
> +			*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 },
This must be broken down into defines showing what the various bits are
doing.

> +	{ MAX44000_REG_CFG_RX,		MAX44000_REG_CFG_RX_DEFAULT },
> +	{ 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,

Please read:
http://www.spinics.net/lists/linux-iio/msg22996.html
You definitely want REGCACHE_RBTREE which behaves quite differently wrt
to what happens on startup of the cache.
> +
If we aren't assuming particular values, what is the purpose of providing
defaults?  They are probably wrong..
> +	.reg_defaults		= max44000_reg_defaults,
> +	.num_reg_defaults	= ARRAY_SIZE(max44000_reg_defaults),
> +};
> +
> +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);
> +	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);
> +
> +	/*
> +	 * The device doesn't have a reset function so we just clear some
> +	 * important bits at probe time to ensure sane operation.
> +	 *
> +	 * Since we don't support interrupts/events the threshold values are
> +	 * not important. We also don't touch trim values.
> +	 */
> +
> +	/* Reset ALS scaling bits */
> +	ret = regmap_write(data->regmap, MAX44000_REG_CFG_RX, MAX44000_REG_CFG_RX_DEFAULT);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "failed to write default CFG_RX: %d\n", ret);
> +		return ret;
> +	}
> +
> +	/* Reset CFG bits to ALS-only mode and no interrupts */
> +	reg = MAX44000_CFG_TRIM | MAX44000_CFG_MODE_ALS_GIR;
> +	ret = regmap_write(data->regmap, MAX44000_REG_CFG_MAIN, reg);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "failed to write init config: %d\n", ret);
> +		return ret;
> +	}
> +
I prefer this careful code making it clear what you are doing on setting the
defaults to the previous wholesale version.

> +	/* Read status at least once to clear any stale interrupt bits. */
> +	ret = regmap_read(data->regmap, MAX44000_REG_STATUS, &reg);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "failed to read init status: %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);
blank line here ideally (nitpick on the day :)
> +	return 0;
> +}
> +
> +static const struct i2c_device_id max44000_id[] = {
> +	{"max44000", 0},
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, max44000_id);
> +
> +#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,
> +		.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");
> 

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