Date:   Mon, 3 Jun 2019 12:11:17 +0100
From:   Jonathan Cameron <jonathan.cameron@...wei.com>
To:     Guenter Roeck <linux@...ck-us.net>
CC:     Serge Semin <fancer.lancer@...il.com>,
        Jean Delvare <jdelvare@...e.com>,
        Serge Semin <Sergey.Semin@...latforms.ru>,
        <linux-kernel@...r.kernel.org>, <linux-hwmon@...r.kernel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        <linux-iio@...r.kernel.org>
Subject: Re: [PATCH 2/2] hwmon: Add ads1000/ads1100 voltage ADCs driver

On Thu, 30 May 2019 05:55:10 -0700
Guenter Roeck <linux@...ck-us.net> wrote:

> Hi,
> 
> On Wed, May 15, 2019 at 01:58:09AM +0300, Serge Semin wrote:
> > These are simple Texas Instruments ADC working over i2c-interface with
> > just one differential input and with configurable 12-16 bits resolution.
> > Sample rate is fixed to 128 for ads1000 and can vary from 8 to 128 for
> > ads1100. Vdd value reference value must be supplied so to properly
> > translate the sampled code to the real voltage. All of these configs are
> > implemented in the device drivers for hwmon subsystem. The next dts
> > properties should be specified to comply the device platform setup:
> >  - vdd-supply - voltage regulator connected to the Vdd pin of the device
> >  - ti,gain - programmable gain amplifier
> >  - ti,datarate - converter data rate
> >  - ti,voltage-divider - possible resistors-base external divider
> > See bindings documentation file for details.
> > 
> > Even though these devices seem more like ads1015 series, they
> > in fact pretty much different. First of all ads1000/ads1100 got less
> > capabilities: just one port, no configurations of digital comparator, no
> > input multi-channel multiplexer, smaller PGA and data-rate ranges.
> > In addition they haven't got internal voltage reference, but instead
> > are created to use Vdd pin voltage. Finally the output code value is
> > provided in different format. As a result it was much easier for
> > development and for future support to create a separate driver.
> >   
> 
> This chicp doesn't have any real hardware monitoring characteristics
> (no limit registers). It seems to be better suited to be implemented
> as iio driver. If it is used as hardware monitor, the iio-hwmon bridge
> should work just fine.
> 
> Jonathan, what do you think ?
Sorry for slow response, was on vacation.

Agreed, this looks like a standard multipurpose ADC so probably more suited
to IIO. Whether you bother with a buffered /chardev interface or not given it
is a fairly slow device is a separate question (can always be added later
when someone wants it).

Note the voltage-divider in the DT properties is something that should
have a generic representation. In IIO we have drivers/iio/afe/iio-rescale.c
for that, in this case using the voltage divider binding.

gain and datarate are both characteristics that should be controlled from
userspace rather than via a binding.

Thanks,

Jonathan
> 
> Thanks,
> Guenter
> 
> > Signed-off-by: Serge Semin <fancer.lancer@...il.com>
> > ---
> >  MAINTAINERS                           |   8 +
> >  drivers/hwmon/Kconfig                 |  10 +
> >  drivers/hwmon/Makefile                |   1 +
> >  drivers/hwmon/ads1000.c               | 320 ++++++++++++++++++++++++++
> >  include/linux/platform_data/ads1000.h |  20 ++
> >  5 files changed, 359 insertions(+)
> >  create mode 100644 drivers/hwmon/ads1000.c
> >  create mode 100644 include/linux/platform_data/ads1000.h
> > 
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index ce573aaa04df..5c3a8107ef1a 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -517,6 +517,14 @@ W:	http://ez.analog.com/community/linux-device-drivers
> >  S:	Supported
> >  F:	drivers/video/backlight/adp8860_bl.c
> >  
> > +ADS1000 HARDWARE MONITOR DRIVER
> > +M:	Serge Semin <fancer.lancer@...il.com>
> > +L:	linux-hwmon@...r.kernel.org
> > +S:	Maintained
> > +F:	Documentation/hwmon/ads1000.rst
> > +F:	drivers/hwmon/ads1000.c
> > +F:	include/linux/platform_data/ads1000.h
> > +
> >  ADS1015 HARDWARE MONITOR DRIVER
> >  M:	Dirk Eibach <eibach@...ys.de>
> >  L:	linux-hwmon@...r.kernel.org
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index 1915a18b537b..a1220cc48f2f 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -1569,6 +1569,16 @@ config SENSORS_ADC128D818
> >  	  This driver can also be built as a module. If so, the module
> >  	  will be called adc128d818.
> >  
> > +config SENSORS_ADS1000
> > +	tristate "Texas Instruments ADS1000"
> > +	depends on I2C
> > +	help
> > +	  If you say yes here you get support for Texas Instruments
> > +	  ADS1000/ADS1100 12-16-bit single channel ADC device.
> > +
> > +	  This driver can also be built as a module.  If so, the module
> > +	  will be called ads1000.
> > +
> >  config SENSORS_ADS1015
> >  	tristate "Texas Instruments ADS1015"
> >  	depends on I2C
> > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > index 8db472ea04f0..2cd82f6c651e 100644
> > --- a/drivers/hwmon/Makefile
> > +++ b/drivers/hwmon/Makefile
> > @@ -35,6 +35,7 @@ obj-$(CONFIG_SENSORS_ADM1026)	+= adm1026.o
> >  obj-$(CONFIG_SENSORS_ADM1029)	+= adm1029.o
> >  obj-$(CONFIG_SENSORS_ADM1031)	+= adm1031.o
> >  obj-$(CONFIG_SENSORS_ADM9240)	+= adm9240.o
> > +obj-$(CONFIG_SENSORS_ADS1000)	+= ads1000.o
> >  obj-$(CONFIG_SENSORS_ADS1015)	+= ads1015.o
> >  obj-$(CONFIG_SENSORS_ADS7828)	+= ads7828.o
> >  obj-$(CONFIG_SENSORS_ADS7871)	+= ads7871.o
> > diff --git a/drivers/hwmon/ads1000.c b/drivers/hwmon/ads1000.c
> > new file mode 100644
> > index 000000000000..a88b738f56bd
> > --- /dev/null
> > +++ b/drivers/hwmon/ads1000.c
> > @@ -0,0 +1,320 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Driver for ADS1000/ADS1100 12-16-bit ADC
> > + *
> > + * Copyright (C) 2019 T-platforms JSC (fancer.lancer@...il.com)
> > + *
> > + * Based on the ads1015 driver by Dirk Eibach.
> > + *
> > + * Datasheet available at: http://focus.ti.com/lit/ds/symlink/ads1000.pdf
> > + */
> > +
> > +#include <linux/module.h>
> > +#include <linux/init.h>
> > +#include <linux/slab.h>
> > +#include <linux/delay.h>
> > +#include <linux/i2c.h>
> > +#include <linux/hwmon.h>
> > +#include <linux/hwmon-sysfs.h>
> > +#include <linux/err.h>
> > +#include <linux/mutex.h>
> > +#include <linux/regulator/consumer.h>
> > +#include <linux/of_device.h>
> > +#include <linux/of.h>
> > +#include <linux/platform_data/ads1000.h>
> > +
> > +/* Data rates scale table */
> > +static const unsigned int scale_table[4] = {
> > +	2048, 8192, 16384, 32768
> > +};
> > +
> > +/* Minimal data rates in samples per second */
> > +static const unsigned int data_rate_table[4] = {
> > +	100, 25, 12, 5
> > +};
> > +
> > +#define ADS1000_DEFAULT_PGA 0
> > +#define ADS1000_DEFAULT_DATA_RATE 0
> > +#define ADS1000_DEFAULT_R1_DIVIDER 0
> > +#define ADS1000_DEFAULT_R2_DIVIDER 0
> > +
> > +enum ads1000_chips {
> > +	ads1000,
> > +	ads1100,
> > +};
> > +
> > +struct ads1000 {
> > +	struct device *hwmon_dev;
> > +	struct mutex update_lock;
> > +	struct i2c_client *client;
> > +	struct ads1000_platform_data data;
> > +	enum ads1000_chips id;
> > +};
> > +
> > +static inline int ads1000_enable_vdd(struct ads1000 *priv)
> > +{
> > +	return regulator_enable(priv->data.vdd);
> > +}
> > +
> > +static inline int ads1000_get_vdd(struct ads1000 *priv)
> > +{
> > +	return regulator_get_voltage(priv->data.vdd);
> > +}
> > +
> > +static int ads1000_read_adc(struct ads1000 *priv)
> > +{
> > +	struct i2c_client *client = priv->client;
> > +	unsigned int delay_ms;
> > +	u8 data[3] = {0};
> > +	int res;
> > +
> > +	mutex_lock(&priv->update_lock);
> > +
> > +	delay_ms = DIV_ROUND_UP(1000, data_rate_table[priv->data.data_rate]);
> > +
> > +	/* setup and start single conversion */
> > +	data[2] |= (1 << 7) | (1 << 4);
> > +	data[2] |= priv->data.pga;
> > +	data[2] |= priv->data.data_rate << 2;
> > +
> > +	res = i2c_master_send(client, &data[2], 1);
> > +	if (res < 0)
> > +		goto err_unlock;
> > +
> > +	/* wait until conversion finished */
> > +	msleep(delay_ms);
> > +	res = i2c_master_recv(client, data, 3);
> > +	if (res < 0)
> > +		goto err_unlock;
> > +
> > +	if (data[2] & (1 << 7)) {
> > +		res = -EIO;
> > +		goto err_unlock;
> > +	}
> > +
> > +	res = ((u16)data[0] << 8) | data[1];
> > +
> > +err_unlock:
> > +	mutex_unlock(&priv->update_lock);
> > +
> > +	return res;
> > +}
> > +
> > +static int ads1000_reg_to_mv(struct ads1000 *priv, s16 reg)
> > +{
> > +	unsigned int *divider = priv->data.divider;
> > +	int voltage = ads1000_get_vdd(priv);
> > +	int gain = 1 << priv->data.pga;
> > +	int c = 0;
> > +
> > +	voltage = reg*DIV_ROUND_CLOSEST(voltage, 1000);
> > +	gain = gain*scale_table[priv->data.data_rate];
> > +	voltage = DIV_ROUND_CLOSEST(voltage, gain);
> > +
> > +	if (divider[0] && divider[1]) {
> > +		c = divider[0]*voltage;
> > +		c = DIV_ROUND_CLOSEST(c, (int)divider[1]);
> > +	}
> > +
> > +	return voltage + c;
> > +}
> > +
> > +static ssize_t show_in(struct device *dev, struct device_attribute *da,
> > +		       char *buf)
> > +{
> > +	struct ads1000 *priv = dev_get_drvdata(dev);
> > +	int res;
> > +
> > +	res = ads1000_read_adc(priv);
> > +	if (res < 0)
> > +		return res;
> > +
> > +	return sprintf(buf, "%d\n", ads1000_reg_to_mv(priv, res));
> > +}
> > +
> > +static SENSOR_DEVICE_ATTR(in0_input, 0444, show_in, NULL, 0);
> > +
> > +static struct attribute *ads1000_attrs[] = {
> > +	&sensor_dev_attr_in0_input.dev_attr.attr,
> > +	NULL
> > +};
> > +ATTRIBUTE_GROUPS(ads1000);
> > +
> > +static struct ads1000 *ads1000_create_priv(struct i2c_client *client,
> > +					   const struct i2c_device_id *id)
> > +{
> > +	struct ads1000 *priv;
> > +
> > +	priv = devm_kzalloc(&client->dev, sizeof(struct ads1000),
> > +			    GFP_KERNEL);
> > +	if (!priv)
> > +		return ERR_PTR(-ENOMEM);
> > +
> > +	if (client->dev.of_node)
> > +		priv->id = (enum ads1000_chips)
> > +			of_device_get_match_data(&client->dev);
> > +	else
> > +		priv->id = id->driver_data;
> > +
> > +	i2c_set_clientdata(client, priv);
> > +	priv->client = client;
> > +	mutex_init(&priv->update_lock);
> > +
> > +	return priv;
> > +}
> > +
> > +#ifdef CONFIG_OF
> > +static int ads1000_get_config_of(struct ads1000 *priv)
> > +{
> > +	struct i2c_client *client = priv->client;
> > +	struct device_node *node = client->dev.of_node;
> > +	u32 divider[2];
> > +	u32 val;
> > +
> > +	if (!node)
> > +		return -EINVAL;
> > +
> > +	if (!of_property_read_u32(node, "ti,gain", &val))
> > +		priv->data.pga = val;
> > +
> > +	if (!of_property_read_u32(node, "ti,datarate", &val))
> > +		priv->data.data_rate = val;
> > +
> > +	if (!of_property_read_u32_array(node, "ti,voltage-divider",
> > +					divider, 2)) {
> > +		priv->data.divider[0] = divider[0];
> > +		priv->data.divider[1] = divider[1];
> > +	}
> > +
> > +	priv->data.vdd = devm_regulator_get(&client->dev, "vdd");
> > +	if (IS_ERR(priv->data.vdd))
> > +		return PTR_ERR(priv->data.vdd);
> > +
> > +	return 0;
> > +}
> > +#endif
> > +
> > +static int ads1000_get_config(struct ads1000 *priv)
> > +{
> > +	struct i2c_client *client = priv->client;
> > +	struct ads1000_platform_data *pdata = dev_get_platdata(&client->dev);
> > +
> > +	priv->data.pga = ADS1000_DEFAULT_PGA;
> > +	priv->data.data_rate = ADS1000_DEFAULT_DATA_RATE;
> > +	priv->data.divider[0] = ADS1000_DEFAULT_R1_DIVIDER;
> > +	priv->data.divider[1] = ADS1000_DEFAULT_R2_DIVIDER;
> > +
> > +	/* prefer platform data */
> > +	if (pdata) {
> > +		memcpy(&priv->data, pdata, sizeof(priv->data));
> > +	} else {
> > +#ifdef CONFIG_OF
> > +		int ret;
> > +
> > +		ret = ads1000_get_config_of(priv);
> > +		if (ret)
> > +			return ret;
> > +#endif
> > +	}
> > +
> > +	if (!priv->data.vdd) {
> > +		dev_err(&client->dev, "No VDD regulator\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	if (priv->data.pga > 4) {
> > +		dev_err(&client->dev, "Invalid gain, using default\n");
> > +		priv->data.pga = ADS1000_DEFAULT_PGA;
> > +	}
> > +
> > +	if (priv->data.data_rate > 4) {
> > +		dev_err(&client->dev, "Invalid datarate, using default\n");
> > +		priv->data.data_rate = ADS1000_DEFAULT_DATA_RATE;
> > +	}
> > +
> > +	if (priv->id == ads1000 && priv->data.data_rate != 0) {
> > +		dev_warn(&client->dev, "ADC data rate can be 128SPS only\n");
> > +		priv->data.data_rate = 0;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int ads1000_set_config(struct ads1000 *priv)
> > +{
> > +	u8 data = 0;
> > +	int ret;
> > +
> > +	/* disable continuous conversion */
> > +	data |= (1 << 4);
> > +	data |= priv->data.pga;
> > +	data |= priv->data.data_rate << 2;
> > +
> > +	ret = i2c_master_send(priv->client, &data, 1);
> > +
> > +	return ret < 0 ? ret : 0;
> > +}
> > +
> > +static int ads1000_probe(struct i2c_client *client,
> > +			 const struct i2c_device_id *id)
> > +{
> > +	struct ads1000 *priv;
> > +	int ret;
> > +
> > +	priv = ads1000_create_priv(client, id);
> > +	if (IS_ERR(priv))
> > +		return PTR_ERR(priv);
> > +
> > +	ret = ads1000_get_config(priv);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = ads1000_enable_vdd(priv);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = ads1000_set_config(priv);
> > +	if (ret)
> > +		return ret;
> > +
> > +	priv->hwmon_dev = devm_hwmon_device_register_with_groups(&client->dev,
> > +				client->name, priv, ads1000_groups);
> > +	if (IS_ERR(priv->hwmon_dev))
> > +		return PTR_ERR(priv->hwmon_dev);
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct i2c_device_id ads1000_id[] = {
> > +	{ "ads1000",  ads1000},
> > +	{ "ads1100",  ads1100},
> > +	{ }
> > +};
> > +MODULE_DEVICE_TABLE(i2c, ads1000_id);
> > +
> > +static const struct of_device_id ads1000_of_match[] = {
> > +	{
> > +		.compatible = "ti,ads1000",
> > +		.data = (void *)ads1000
> > +	},
> > +	{
> > +		.compatible = "ti,ads1100",
> > +		.data = (void *)ads1100
> > +	},
> > +	{ },
> > +};
> > +MODULE_DEVICE_TABLE(of, ads1000_of_match);
> > +
> > +static struct i2c_driver ads1000_driver = {
> > +	.driver = {
> > +		.name = "ads1000",
> > +		.of_match_table = of_match_ptr(ads1000_of_match),
> > +	},
> > +	.probe = ads1000_probe,
> > +	.id_table = ads1000_id,
> > +};
> > +module_i2c_driver(ads1000_driver);
> > +
> > +MODULE_AUTHOR("Serge Semin <fancer.lancer@...il.com>");
> > +MODULE_DESCRIPTION("ADS1000 driver");
> > +MODULE_LICENSE("GPL v2");
> > diff --git a/include/linux/platform_data/ads1000.h b/include/linux/platform_data/ads1000.h
> > new file mode 100644
> > index 000000000000..979670483537
> > --- /dev/null
> > +++ b/include/linux/platform_data/ads1000.h
> > @@ -0,0 +1,20 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Platform Data for ADS1000/ADS1100 12-16-bit ADC
> > + *
> > + * Copyright (C) 2019 T-platforms JSC (fancer.lancer@...il.com)
> > + */
> > +
> > +#ifndef LINUX_ADS1000_H
> > +#define LINUX_ADS1000_H
> > +
> > +#include <linux/regulator/consumer.h>
> > +
> > +struct ads1000_platform_data {
> > +	unsigned int pga;
> > +	unsigned int data_rate;
> > +	struct regulator *vdd;
> > +	unsigned int divider[2];
> > +};
> > +
> > +#endif /* LINUX_ADS1000_H */  

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