Message-ID: <20190607230144.fnkzljhnnqks5oqx@mobilestation>
Date:   Sat, 8 Jun 2019 02:01:46 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Jonathan Cameron <jonathan.cameron@...wei.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

Hello folks

On Wed, Jun 05, 2019 at 01:55:56PM -0700, Guenter Roeck wrote:
> On Mon, Jun 03, 2019 at 12:11:17PM +0100, Jonathan Cameron wrote:
> > 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.
> > 
> 
> In summary: Serge, please re-implement the driver as iio adc driver.
> 

Thanks for the comments. I see your point, but since you are asking of a pretty
much serious code redevelopment, I want to make sure it is fully justified.

I made my decision of creating the hwmon driver following the next logic.
Before I started this driver development, I searched the kernel for either a
ready-to-use code or for a similar device driver to add the ads1000 ADC support.
I found the ads1015 driver, which is created for TI ADC1015 ADCs. These devices
are similar to the ads1000 series, but are more complex. Due to the complexity
I decided to create a separate driver for ads1000s, and of course since the similar
device driver lived in hwmon, I chose it to be home of my new driver.

But now you are asking me to move it to IIO, while the driver of more complex
ads1015 device exists in the hwmon subsystem of the kernel. Moreover the ads1000
device is utilized on our board to monitor system itself (voltage on the input
DC-DC). Could you please tell me why the driver should really be in IIO instead
of hwmon and how do you select which subsystem one or another driver is supposed
to live in?

Regards,
-Sergey

> Thanks,
> Guenter
> 
> > 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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