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Date: Thu, 29 Jun 2017 06:34:22 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Mike Looijmans <mike.looijmans@...ic.nl>,
linux-hwmon@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, Jonathan Cameron <jic23@...nel.org>,
linux-iio@...r.kernel.org, jdelvare@...e.com
Subject: Re: [PATCH] hwmon: Add LTC2471/LTC2473 driver
On 06/29/2017 03:45 AM, Mike Looijmans wrote:
> The LTC2741 and LTC2473 are single voltage monitoring chips. The LTC2473
> is similar to the LTC2471 but outputs a signed differential value.
>
> Datasheet:
> http://cds.linear.com/docs/en/datasheet/24713fb.pdf
>
> Signed-off-by: Mike Looijmans <mike.looijmans@...ic.nl>
Hi Mike,
that looks like a perfect candidate for an iio driver, since its use is
not limited to hardware monitoring, it has a high sample rate, and it
doesn't have limit registers or actions.
Jonathan, what do you think ?
Thanks,
Guenter
> ---
> drivers/hwmon/Kconfig | 10 ++++
> drivers/hwmon/Makefile | 1 +
> drivers/hwmon/ltc2471.c | 127 ++++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 138 insertions(+)
> create mode 100644 drivers/hwmon/ltc2471.c
>
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index fbde226..c9a2a87 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -673,6 +673,16 @@ config SENSORS_LINEAGE
> This driver can also be built as a module. If so, the module
> will be called lineage-pem.
>
> +config SENSORS_LTC2471
> + tristate "Linear Technology LTC2471 and LTC2473"
> + depends on I2C
> + help
> + If you say yes here you get support for Linear Technology LTC2471
> + and LTC2473 voltage monitors.
> +
> + This driver can also be built as a module. If so, the module will
> + be called ltc2471.
> +
> config SENSORS_LTC2945
> tristate "Linear Technology LTC2945"
> depends on I2C
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 58cc3ac..6f60fe7 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -99,6 +99,7 @@ obj-$(CONFIG_SENSORS_LM93) += lm93.o
> obj-$(CONFIG_SENSORS_LM95234) += lm95234.o
> obj-$(CONFIG_SENSORS_LM95241) += lm95241.o
> obj-$(CONFIG_SENSORS_LM95245) += lm95245.o
> +obj-$(CONFIG_SENSORS_LTC2471) += ltc2471.o
> obj-$(CONFIG_SENSORS_LTC2945) += ltc2945.o
> obj-$(CONFIG_SENSORS_LTC2990) += ltc2990.o
> obj-$(CONFIG_SENSORS_LTC4151) += ltc4151.o
> diff --git a/drivers/hwmon/ltc2471.c b/drivers/hwmon/ltc2471.c
> new file mode 100644
> index 0000000..17eaad8
> --- /dev/null
> +++ b/drivers/hwmon/ltc2471.c
> @@ -0,0 +1,127 @@
> +/*
> + * Driver for Linear Technology LTC2471 and LTC2473 voltage monitors
> + * The LTC2473 is identical to the 2471, but reports a differential signal.
> + *
> + * Copyright (C) 2017 Topic Embedded Products
> + * Author: Mike Looijmans <mike.looijmans@...ic.nl>
> + *
> + * License: GPLv2
> + */
> +
> +#include <linux/err.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>
> +#include <linux/i2c.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +
> +enum chips {
> + ltc2471,
> + ltc2473
> +};
> +
> +struct ltc2471_data {
> + struct i2c_client *i2c;
> + bool differential;
> +};
> +
> +/* Reference voltage is 1.25V */
> +#define LTC2471_VREF 1250
> +
> +/* Read two bytes from the I2C bus to obtain the ADC result */
> +static int ltc2471_get_value(struct i2c_client *i2c)
> +{
> + int ret;
> + __be16 buf;
> +
> + ret = i2c_master_recv(i2c, (char *)&buf, 2);
> + if (ret < 0)
> + return ret;
> + if (ret != 2)
> + return -EIO;
> +
> + /* MSB first */
> + return be16_to_cpu(buf);
> +}
> +
> +static ssize_t ltc2471_show_value(struct device *dev,
> + struct device_attribute *da, char *buf)
> +{
> + struct ltc2471_data *data = dev_get_drvdata(dev);
> + int value;
> +
> + value = ltc2471_get_value(data->i2c);
> + if (unlikely(value < 0))
> + return value;
> +
> + if (data->differential)
> + /* Ranges from -VREF to +VREF with "0" at 0x8000 */
> + value = ((s32)LTC2471_VREF * (s32)(value - 0x8000)) >> 15;
> + else
> + /* Ranges from 0 to +VREF */
> + value = ((u32)LTC2471_VREF * (u32)value) >> 16;
> +
> + return snprintf(buf, PAGE_SIZE, "%d\n", value);
> +}
> +
> +static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, ltc2471_show_value, NULL, 0);
> +
> +static struct attribute *ltc2471_attrs[] = {
> + &sensor_dev_attr_in0_input.dev_attr.attr,
> + NULL
> +};
> +
> +ATTRIBUTE_GROUPS(ltc2471);
> +
> +static int ltc2471_i2c_probe(struct i2c_client *i2c,
> + const struct i2c_device_id *id)
> +{
> + int ret;
> + struct device *hwmon_dev;
> + struct ltc2471_data *data;
> +
> + if (!i2c_check_functionality(i2c->adapter, I2C_FUNC_I2C))
> + return -ENODEV;
> +
> + data = devm_kzalloc(&i2c->dev, sizeof(struct ltc2471_data), GFP_KERNEL);
> + if (unlikely(!data))
> + return -ENOMEM;
> +
> + data->i2c = i2c;
> + data->differential = (id->driver_data == ltc2473);
> +
> + /* Trigger once to start conversion and check if chip is there */
> + ret = ltc2471_get_value(i2c);
> + if (ret < 0) {
> + dev_err(&i2c->dev, "Cannot read from device.\n");
> + return ret;
> + }
> +
> + hwmon_dev = devm_hwmon_device_register_with_groups(&i2c->dev,
> + i2c->name,
> + data,
> + ltc2471_groups);
> +
> + return PTR_ERR_OR_ZERO(hwmon_dev);
> +}
> +
> +static const struct i2c_device_id ltc2471_i2c_id[] = {
> + { "ltc2471", ltc2471 },
> + { "ltc2473", ltc2473 },
> + {}
> +};
> +MODULE_DEVICE_TABLE(i2c, ltc2471_i2c_id);
> +
> +static struct i2c_driver ltc2471_i2c_driver = {
> + .driver = {
> + .name = "ltc2471",
> + },
> + .probe = ltc2471_i2c_probe,
> + .id_table = ltc2471_i2c_id,
> +};
> +
> +module_i2c_driver(ltc2471_i2c_driver);
> +
> +MODULE_DESCRIPTION("LTC2471/LTC2473 Sensor Driver");
> +MODULE_AUTHOR("Topic Embedded Products");
> +MODULE_LICENSE("GPL v2");
>
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