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Message-ID: <20130626143927.GB31998@roeck-us.net>
Date: Wed, 26 Jun 2013 07:39:27 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Cc: Shawn Guo <shawn.guo@...aro.org>,
Jean Delvare <khali@...ux-fr.org>, jimwall@...om,
brian@...stalfontz.com,
Maxime Ripard <maxime.ripard@...e-electrons.com>,
Grant Likely <grant.likely@...aro.org>,
Rob Herring <rob.herring@...xeda.com>,
Rob Landley <rob@...dley.net>,
Russell King <linux@....linux.org.uk>,
devicetree-discuss@...ts.ozlabs.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, lm-sensors@...sensors.org,
linux-arm-kernel@...ts.infradead.org, linux-iio@...r.kernel.org
Subject: Re: [PATCH 3/4] hwmon: Add a simple driver to read the MXS SoC
temperature
On Wed, Jun 26, 2013 at 10:51:12AM +0200, Alexandre Belloni wrote:
> The low resolution ADC of the mxs is able to read an internal temperature
> sensor, expose that using hwmon.
>
> Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
> ---
Wouldn't it make more sense to use iio-hwmon and improve it if necessary ?
Guenter
> .../devicetree/bindings/hwmon/mxs-cputemp.txt | 18 +++
> Documentation/hwmon/mxs-cputemp | 29 +++++
> drivers/hwmon/Kconfig | 10 ++
> drivers/hwmon/Makefile | 1 +
> drivers/hwmon/mxs-cputemp.c | 132 +++++++++++++++++++++
> 5 files changed, 190 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/hwmon/mxs-cputemp.txt
> create mode 100644 Documentation/hwmon/mxs-cputemp
> create mode 100644 drivers/hwmon/mxs-cputemp.c
>
> diff --git a/Documentation/devicetree/bindings/hwmon/mxs-cputemp.txt b/Documentation/devicetree/bindings/hwmon/mxs-cputemp.txt
> new file mode 100644
> index 0000000..7d3ae47
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/hwmon/mxs-cputemp.txt
> @@ -0,0 +1,18 @@
> +mxs cputemp hwmon sensors
> +-------------------------
> +
> +See: Documentation/hwmon/mxs-cputemp
> +
> +Required properties:
> +- compatible: should be "fsl,mxs-internal-temp"
> +- io-channels: should list the two adc channels needed to calculate the
> + temperature
> +- io-channel-names: should map the previously listed adc channels to the "min"
> + and "max" value
> +
> +Example:
> + temp {
> + compatible = "fsl,mxs-internal-temp";
> + io-channels = <&lradc 8>, <&lradc 9>;
> + io-channel-names = "min", "max";
> + };
> diff --git a/Documentation/hwmon/mxs-cputemp b/Documentation/hwmon/mxs-cputemp
> new file mode 100644
> index 0000000..6c6201f
> --- /dev/null
> +++ b/Documentation/hwmon/mxs-cputemp
> @@ -0,0 +1,29 @@
> +Kernel driver mxs-cputemp
> +=========================
> +
> +Supported chips:
> + * Freescale i.mx28
> + Datasheet: i.MX28 Applications Processor Reference Manual, Rev. 1, 2010
> + http://cache.freescale.com/files/dsp/doc/ref_manual/MCIMX28RM.pdf
> +
> +Author: Alexandre Belloni
> +
> +Description
> +-----------
> +This driver permits reading the internal die temperature sensor embedded inside
> +Freescale i.mx28 SoCs. This sensor is read through two channels of the on chip
> +Low-Resolution ADC. After calculation, the three-sigma error of the temperature
> +sensor should be within ± 1.5% in degrees Kelvin. Additionally, the temperature
> +sampling has a three-sigma sample-to-sample variation of 2 degrees Kelvin. If
> +desired, this error can be removed by oversampling and averaging the temperature
> +result.
> +
> +The formula is:
> + (Channel9 – Channel8) * Gain_correction/4
> +
> +As recommended by the datasheet, Gain_correction is equal to 1.012.
> +
> +sysfs entries
> +-------------
> +temp1_input Measured and corrected temperature in millidegrees Celsius
> +
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 0428e8a..2daf794 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -929,6 +929,16 @@ config SENSORS_MCP3021
> This driver can also be built as a module. If so, the module
> will be called mcp3021.
>
> +config SENSORS_MXS_CPU
> + tristate "MXS internal CPU temperature sensor"
> + depends on MXS_LRADC
> + help
> + If you say yes here you get support for the i.mx28 internal
> + temperature sensor.
> +
> + This driver can also be built as a module. If so, the module
> + will be called mxs-cputemp
> +
> config SENSORS_NCT6775
> tristate "Nuvoton NCT6775F and compatibles"
> depends on !PPC
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index d17d3e6..366c92d 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -108,6 +108,7 @@ obj-$(CONFIG_SENSORS_MAX6650) += max6650.o
> obj-$(CONFIG_SENSORS_MAX6697) += max6697.o
> obj-$(CONFIG_SENSORS_MC13783_ADC)+= mc13783-adc.o
> obj-$(CONFIG_SENSORS_MCP3021) += mcp3021.o
> +obj-$(CONFIG_SENSORS_MXS_CPU) += mxs-cputemp.o
> obj-$(CONFIG_SENSORS_NCT6775) += nct6775.o
> obj-$(CONFIG_SENSORS_NTC_THERMISTOR) += ntc_thermistor.o
> obj-$(CONFIG_SENSORS_PC87360) += pc87360.o
> diff --git a/drivers/hwmon/mxs-cputemp.c b/drivers/hwmon/mxs-cputemp.c
> new file mode 100644
> index 0000000..a312fb5
> --- /dev/null
> +++ b/drivers/hwmon/mxs-cputemp.c
> @@ -0,0 +1,132 @@
> +/*
> + * Driver for the mxs internal temperature sensor
> + *
> + * Copyright 2013 Free Electrons
> + *
> + * Licensed under the GPLv2 or later.
> + */
> +
> +#define DRVNAME "mxs-hwmon"
> +
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/iio/consumer.h>
> +
> +#define GAIN_CORRECTION 1012
> +
> +/* The value we calculate from the ADCs is in Kelvins, don't forget to convert
> + * it to Celsius */
> +#define VALUES_TO_MILLIC(min, max) ((max - min) * GAIN_CORRECTION / 4 - 272150)
> +
> +struct mxs_hwmon_data {
> + struct device *hwmon_dev;
> + struct iio_channel *chan_min;
> + struct iio_channel *chan_max;
> +};
> +
> +static int mxs_hwmon_show_temp(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + int err, val_min, val_max;
> +
> + struct mxs_hwmon_data *data = dev_get_drvdata(dev);
> +
> + err = iio_read_channel_raw(data->chan_min, &val_min);
> + if (err < 0)
> + return err;
> +
> + err = iio_read_channel_raw(data->chan_max, &val_max);
> + if (err < 0)
> + return err;
> +
> + return sprintf(buf, "%u\n", VALUES_TO_MILLIC(val_min, val_max));
> +}
> +
> +static DEVICE_ATTR(temp1_input, S_IRUGO, mxs_hwmon_show_temp, NULL);
> +
> +static int mxs_hwmon_probe(struct platform_device *pdev)
> +{
> + int err;
> + struct mxs_hwmon_data *data;
> +
> + data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
> + if (!data)
> + return -ENOMEM;
> +
> + platform_set_drvdata(pdev, data);
> +
> + err = device_create_file(&pdev->dev, &dev_attr_temp1_input);
> + if (err)
> + return err;
> +
> + data->chan_min = iio_channel_get(&pdev->dev, "min");
> + if (IS_ERR(data->chan_min)) {
> + err = PTR_ERR(data->chan_min);
> + goto error_chan_min;
> + }
> +
> + data->chan_max = iio_channel_get(&pdev->dev, "max");
> + if (IS_ERR(data->chan_max)) {
> + err = PTR_ERR(data->chan_max);
> + goto error_chan_max;
> + }
> +
> + data->hwmon_dev = hwmon_device_register(&pdev->dev);
> + if (IS_ERR(data->hwmon_dev)) {
> + err = PTR_ERR(data->hwmon_dev);
> + goto error_hwmon;
> + }
> +
> + return 0;
> +
> +error_hwmon:
> + iio_channel_release(data->chan_max);
> +error_chan_max:
> + iio_channel_release(data->chan_min);
> +error_chan_min:
> + device_remove_file(&pdev->dev, &dev_attr_temp1_input);
> +
> + return err;
> +}
> +
> +static int mxs_hwmon_remove(struct platform_device *pdev)
> +{
> + struct mxs_hwmon_data *data = platform_get_drvdata(pdev);
> +
> + iio_channel_release(data->chan_min);
> + iio_channel_release(data->chan_max);
> + hwmon_device_unregister(data->hwmon_dev);
> +
> + device_remove_file(&pdev->dev, &dev_attr_temp1_input);
> +
> + return 0;
> +}
> +
> +static struct of_device_id mxs_hwmon_of_match[] = {
> + { .compatible = "fsl,mxs-internal-temp", },
> + {}
> +};
> +MODULE_DEVICE_TABLE(of, mxs_hwmon_of_match);
> +
> +static struct platform_driver mxs_hwmon_driver = {
> + .probe = mxs_hwmon_probe,
> + .remove = mxs_hwmon_remove,
> + .driver = {
> + .name = DRVNAME,
> + .owner = THIS_MODULE,
> + .of_match_table = mxs_hwmon_of_match,
> + },
> +};
> +
> +module_platform_driver(mxs_hwmon_driver);
> +
> +MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@...e-electrons.com>");
> +MODULE_DESCRIPTION("Freescale i.MX28 hwmon sensor driver");
> +MODULE_LICENSE("GPL v2");
> +MODULE_ALIAS("platform:mxs-hwmon");
> --
> 1.8.1.2
>
>
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