[PATCH V2 1/2] thermal: generic-adc: Add DT binding for ADC based thermal sensor

[PATCH V2 1/2] thermal: generic-adc: Add DT binding for ADC based thermal sensor

[Laxman Dewangan]

Sometimes, thermal sensors like NCT thermistors are connected to
the ADC channel. The temperature is read by reading the voltage
across the sensor resistance via ADC and referring the lookup
table for ADC value to temperature.

Add DT binding doc for the ADC based thermal sensor driver to
detail the DT property and provide the example for how to use it.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>

---
Changes from V1:
- Make the lookup table to two dimensional instead of single array of linear
  step of temperature.
- Remove detailing of IIO frameowrk and drivers.
- Added proper braces, indenting and labels.

 .../bindings/thermal/thermal-generic-adc.txt       | 86 ++++++++++++++++++++++
 1 file changed, 86 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/thermal/thermal-generic-adc.txt

diff --git a/Documentation/devicetree/bindings/thermal/thermal-generic-adc.txt b/Documentation/devicetree/bindings/thermal/thermal-generic-adc.txt
new file mode 100644
index 0000000..c5c2e5b
--- /dev/null
+++ b/Documentation/devicetree/bindings/thermal/thermal-generic-adc.txt
@@ -0,0 +1,86 @@
+General Purpose Analog To Digital Converter (ADC) based thermal sensor.
+
+On some of platforms, thermal sensor like thermistors are connected to
+one of ADC channel and sensor resistance is read via voltage across the
+sensor resistor. The voltage read across the sensor is mapped to
+temperature using voltage-temperature lookup table.
+
+Required properties:
+===================
+- compatible:		     Must be "generic-adc-thermal".
+- temperature-lookup-table:  Two dimensional array of Integer; lookup table
+			     to map the relation between ADC value and
+			     temperature. When ADC is read, the value is
+			     looked up on the table to get the equivalent
+			     temperature.
+- #thermal-sensor-cells:     Should be 1. See ./thermal.txt for a description
+			     of this property.
+
+Example :
+#include <dt-bindings/thermal/thermal.h>
+
+i2c@7000c400 {
+	ads1015: ads1015@4a {
+		reg = <0x4a>;
+		compatible = "ads1015";
+		sampling-frequency = <3300>;
+		#io-channel-cells = <1>;
+	};
+};
+
+tboard_thermistor: thermal-sensor@1 {
+	compatible = "generic-adc-thermal";
+	#thermal-sensor-cells = <0>;
+	io-channels = <&ads1015 1>;
+	io-channel-names = "sensor-channel";
+	temperature-lookup-table = <    (-40000) 2578
+					(-39000) 2577
+					(-38000) 2576
+					(-37000) 2575
+					(-36000) 2574
+					(-35000) 2573
+					(-34000) 2572
+					(-33000) 2571
+					(-32000) 2569
+					(-31000) 2568
+					(-30000) 2567
+					::::::::::
+					118000 254
+					119000 247
+					120000 240
+					121000 233
+					122000 226
+					123000 220
+					124000 214
+					125000 208>;
+};
+
+dummy_cool_dev: dummy-cool-dev {
+	compatible = "dummy-cooling-dev";
+	#cooling-cells = <2>; /* min followed by max */
+};
+
+thermal-zones {
+	Tboard {
+		polling-delay = <15000>; /* milliseconds */
+		polling-delay-passive = <0>; /* milliseconds */
+		thermal-sensors = <&tboard_thermistor>;
+
+		trips {
+			therm_est_trip: therm_est_trip {
+				temperature = <40000>;
+				type = "active";
+				hysteresis = <1000>;
+			};
+		};
+
+		cooling-maps {
+			map0 {
+				trip = <&therm_est_trip>;
+				cooling-device = <&dummy_cool_dev THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
+				contribution = <100>;
+			};
+
+		};
+	};
+};
-- 
2.1.4

[PATCH V2 2/2] thermal: generic-adc: Add ADC based thermal sensor driver

[Laxman Dewangan]

Sometimes, thermal sensors like NCT thermistors are connected to
the ADC channel. The temperature is read by reading the voltage
across the sensor resistance via ADC and referring the lookup
table for ADC value to temperature.  The ADC interface is provided
through the IIO framework.

Add support for thermal sensor driver which read the sensor
data through IIO framework which has ADC driver as HW driver.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>

---
Changes from V1:
- Use the two dimensional lookup table for temperature vs ADC value.
- Use non devm_ for thermal zone sensor registration as there may be
  race between IIO channel release and temperature read.

 drivers/thermal/Kconfig               |  10 ++
 drivers/thermal/Makefile              |   1 +
 drivers/thermal/thermal-generic-adc.c | 195 ++++++++++++++++++++++++++++++++++
 3 files changed, 206 insertions(+)
 create mode 100644 drivers/thermal/thermal-generic-adc.c

diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
index 594748e..d7d0136 100644
--- a/drivers/thermal/Kconfig
+++ b/drivers/thermal/Kconfig
@@ -400,4 +400,14 @@ config QCOM_SPMI_TEMP_ALARM
 	  real time die temperature if an ADC is present or an estimate of the
 	  temperature based upon the over temperature stage value.
 
+config GENERIC_ADC_THERMAL
+	tristate "Generic ADC based thermal sensor"
+	depends on IIO
+	help
+	  This enabled a thermal sysfs driver for the temperature sensor
+	  which is connected to the General Purpose ADC. The ADC channel
+	  is read via IIO framework and the channel information is provided
+	  to this driver. This driver reports the temperature by reading ADC
+	  channel and converts it to temperature based on lookup table.
+
 endif
diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
index d64f7f7..904593a 100644
--- a/drivers/thermal/Makefile
+++ b/drivers/thermal/Makefile
@@ -49,3 +49,4 @@ obj-$(CONFIG_ST_THERMAL)	+= st/
 obj-$(CONFIG_TEGRA_SOCTHERM)	+= tegra/
 obj-$(CONFIG_HISI_THERMAL)     += hisi_thermal.o
 obj-$(CONFIG_MTK_THERMAL)	+= mtk_thermal.o
+obj-$(CONFIG_GENERIC_ADC_THERMAL)	+= thermal-generic-adc.o
diff --git a/drivers/thermal/thermal-generic-adc.c b/drivers/thermal/thermal-generic-adc.c
new file mode 100644
index 0000000..902cf12
--- /dev/null
+++ b/drivers/thermal/thermal-generic-adc.c
@@ -0,0 +1,195 @@
+/*
+ * Generic ADC thermal driver
+ *
+ * Copyright (C) 2016 NVIDIA CORPORATION. All rights reserved.
+ *
+ * Author: Laxman Dewangan <ldewangan@nvidia.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#include <linux/iio/consumer.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/thermal.h>
+
+struct gadc_thermal_info {
+	struct device *dev;
+	struct thermal_zone_device *tz_dev;
+	struct iio_channel *channel;
+	s32 *lookup_table;
+	int nlookup_table;
+};
+
+static int gadc_thermal_read_channel(struct gadc_thermal_info *gti, int *val)
+{
+	int ret;
+
+	ret = iio_read_channel_processed(gti->channel, val);
+	if (ret < 0)
+		ret = iio_read_channel_raw(gti->channel, val);
+	if (ret < 0)
+		return ret;
+
+	return ret;
+}
+
+static int gadc_thermal_adc_to_temp(struct gadc_thermal_info *gti, int val)
+{
+	int temp, adc_hi, adc_lo;
+	int i;
+
+	for (i = 0; i < gti->nlookup_table; i++) {
+		if (val >= gti->lookup_table[2 * i + 1])
+			break;
+	}
+
+	if (i == 0) {
+		temp = gti->lookup_table[0];
+	} else if (i >= (gti->nlookup_table - 1)) {
+		temp = gti->lookup_table[2 * (gti->nlookup_table - 1)];
+	} else {
+		adc_hi = gti->lookup_table[2 * i - 1];
+		adc_lo = gti->lookup_table[2 * i + 1];
+		temp = gti->lookup_table[2 * i];
+		temp -= ((val - adc_lo) * 1000) / (adc_hi - adc_lo);
+	}
+
+	return temp;
+}
+
+static int gadc_thermal_get_temp(void *data, int *temp)
+{
+	struct gadc_thermal_info *gti = data;
+	int val;
+	int ret;
+
+	ret = gadc_thermal_read_channel(gti, &val);
+	if (ret < 0) {
+		dev_err(gti->dev, "IIO channel read failed %d\n", ret);
+		return ret;
+	}
+	*temp = gadc_thermal_adc_to_temp(gti, val);
+
+	return 0;
+}
+
+static const struct thermal_zone_of_device_ops gadc_thermal_ops = {
+	.get_temp = gadc_thermal_get_temp,
+};
+
+static int gadc_thermal_read_linear_lookup_table(struct device *dev,
+						 struct gadc_thermal_info *gti)
+{
+	struct device_node *np = dev->of_node;
+	int ntable;
+	int ret;
+
+	ntable = of_property_count_elems_of_size(np, "temperature-lookup-table",
+						 sizeof(u32));
+	if (ntable < 0) {
+		dev_err(dev, "Lookup table is not provided\n");
+		return ntable;
+	}
+
+	if (ntable % 2) {
+		dev_err(dev, "Pair of temperature vs ADC read value missing\n");
+		return -EINVAL;
+	}
+
+	gti->lookup_table = devm_kzalloc(dev, sizeof(*gti->lookup_table) *
+					 ntable, GFP_KERNEL);
+	if (!gti->lookup_table)
+		return -ENOMEM;
+
+	ret = of_property_read_u32_array(np, "temperature-lookup-table",
+					 (u32 *)gti->lookup_table, ntable);
+	if (ret < 0) {
+		dev_err(dev, "Failed to read temperature lookup table: %d\n",
+			ret);
+		return ret;
+	}
+
+	gti->nlookup_table = ntable / 2;
+
+	return 0;
+}
+
+static int gadc_thermal_probe(struct platform_device *pdev)
+{
+	struct gadc_thermal_info *gti;
+	int ret;
+
+	if (!pdev->dev.of_node) {
+		dev_err(&pdev->dev, "Only DT based supported\n");
+		return -ENODEV;
+	}
+
+	gti = devm_kzalloc(&pdev->dev, sizeof(*gti), GFP_KERNEL);
+	if (!gti)
+		return -ENOMEM;
+
+	ret = gadc_thermal_read_linear_lookup_table(&pdev->dev, gti);
+	if (ret < 0)
+		return ret;
+
+	gti->dev = &pdev->dev;
+	platform_set_drvdata(pdev, gti);
+
+	gti->channel = iio_channel_get(&pdev->dev, "sensor-channel");
+	if (IS_ERR(gti->channel)) {
+		ret = PTR_ERR(gti->channel);
+		dev_err(&pdev->dev, "IIO channel not found: %d\n", ret);
+		return ret;
+	}
+
+	gti->tz_dev = thermal_zone_of_sensor_register(&pdev->dev, 0,
+						      gti, &gadc_thermal_ops);
+	if (IS_ERR(gti->tz_dev)) {
+		ret = PTR_ERR(gti->tz_dev);
+		dev_err(&pdev->dev, "Thermal zone sensor register failed: %d\n",
+			ret);
+		goto sensor_fail;
+	}
+
+	return 0;
+
+sensor_fail:
+	iio_channel_release(gti->channel);
+
+	return ret;
+}
+
+static int gadc_thermal_remove(struct platform_device *pdev)
+{
+	struct gadc_thermal_info *gti = platform_get_drvdata(pdev);
+
+	thermal_zone_of_sensor_unregister(&pdev->dev, gti->tz_dev);
+	iio_channel_release(gti->channel);
+
+	return 0;
+}
+
+static const struct of_device_id of_adc_thermal_match[] = {
+	{ .compatible = "generic-adc-thermal", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, of_adc_thermal_match);
+
+static struct platform_driver gadc_thermal_driver = {
+	.driver = {
+		.name = "generic-adc-thermal",
+		.of_match_table = of_adc_thermal_match,
+	},
+	.probe = gadc_thermal_probe,
+	.remove = gadc_thermal_remove,
+};
+
+module_platform_driver(gadc_thermal_driver);
+
+MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
+MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
+MODULE_LICENSE("GPL v2");
-- 
2.1.4

Re: [PATCH V2 1/2] thermal: generic-adc: Add DT binding for ADC based thermal sensor

[Rob Herring]

On Mon, Apr 11, 2016 at 07:11:41PM +0530, Laxman Dewangan wrote:
> Sometimes, thermal sensors like NCT thermistors are connected to
> the ADC channel. The temperature is read by reading the voltage
> across the sensor resistance via ADC and referring the lookup
> table for ADC value to temperature.
> 
> Add DT binding doc for the ADC based thermal sensor driver to
> detail the DT property and provide the example for how to use it.
> 
> Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
> 
> ---
> Changes from V1:
> - Make the lookup table to two dimensional instead of single array of linear
>   step of temperature.
> - Remove detailing of IIO frameowrk and drivers.
> - Added proper braces, indenting and labels.
> 
>  .../bindings/thermal/thermal-generic-adc.txt       | 86 ++++++++++++++++++++++
>  1 file changed, 86 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/thermal/thermal-generic-adc.txt
> 
> diff --git a/Documentation/devicetree/bindings/thermal/thermal-generic-adc.txt b/Documentation/devicetree/bindings/thermal/thermal-generic-adc.txt
> new file mode 100644
> index 0000000..c5c2e5b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/thermal/thermal-generic-adc.txt
> @@ -0,0 +1,86 @@
> +General Purpose Analog To Digital Converter (ADC) based thermal sensor.
> +
> +On some of platforms, thermal sensor like thermistors are connected to
> +one of ADC channel and sensor resistance is read via voltage across the
> +sensor resistor. The voltage read across the sensor is mapped to
> +temperature using voltage-temperature lookup table.
> +
> +Required properties:
> +===================
> +- compatible:		     Must be "generic-adc-thermal".
> +- temperature-lookup-table:  Two dimensional array of Integer; lookup table
> +			     to map the relation between ADC value and
> +			     temperature. When ADC is read, the value is
> +			     looked up on the table to get the equivalent
> +			     temperature.

First value is ?, 2nd value is ? The units are milliCelsius?

> +- #thermal-sensor-cells:     Should be 1. See ./thermal.txt for a description
> +			     of this property.
> +
> +Example :
> +#include <dt-bindings/thermal/thermal.h>
> +
> +i2c@7000c400 {
> +	ads1015: ads1015@4a {
> +		reg = <0x4a>;
> +		compatible = "ads1015";
> +		sampling-frequency = <3300>;
> +		#io-channel-cells = <1>;
> +	};
> +};
> +
> +tboard_thermistor: thermal-sensor@1 {

Drop the unit address.

> +	compatible = "generic-adc-thermal";