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

[PATCH 1/2] thermal: generic-adc: Add DT binding for 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 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>
---
 .../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..6b3e715
--- /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. The voltage read across the sensor is mapped to temperature using
+voltage-temperature lookup table.
+
+This driver provides the interface to sensor-ADC interconnection and
+the relation ship between ADC read value and temperature.
+
+Required properties:
+===================
+- compatible:		     Must be "generic-adc-thermal".
+- lower-temperature:	     Lower temperature for the lookup table
+			     in millicelsius.
+- upper-temperature:	     Upper temperature for the lookup table
+			     in millicelsius.
+- step-temperature:	     The temperature steps for the reading ADC
+			     value in millicelsius.
+- temperature-lookup-table:  The ADC reading value on each step of the
+			     temperature starting from lower temperature
+			     to upper 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>; 
+	};
+};
+
+thermal-sensor@1 {
+	compatible = "generic-adc-thermal";
+	#thermal-sensor-cells = <0>;
+	io-channels = <&ads1015 1>; 
+	io-channel-names = "sensor-channel";
+	lower-temperature = <(-40000)>;
+	upper-temperature = <125000>;
+	step-temperature = <1000>;
+	temperature-lookup-table = <2578 2577 2576 2575 2574
+				2573 2572 2571 2569 2568
+				2567 2565 2563 2561 2559
+				::::::::::
+				254 247 240 233 226 220 
+				214 208>;
+};
+
+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>;
+			writable;
+		};
+	};
+
+	cooling-maps {
+		map0 {
+			trip = <&therm_est_trip>;
+			cooling-device = <&dummy_cool_dev THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
+			contribution = <100>;
+			cdev-type = "therm_est_activ";
+			};
+		};
+
+	};
+};
-- 
2.1.4

[PATCH 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>
---
 drivers/thermal/Kconfig               |  10 ++
 drivers/thermal/Makefile              |   1 +
 drivers/thermal/thermal-generic-adc.c | 208 ++++++++++++++++++++++++++++++++++
 3 files changed, 219 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..6494d86
--- /dev/null
+++ b/drivers/thermal/thermal-generic-adc.c
@@ -0,0 +1,208 @@
+/*
+ * 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 lower_temp;
+	s32 upper_temp;
+	u32 step_temp;
+	int nsteps;
+	u32 *lookup_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->nsteps; i++) {
+		if (val >= gti->lookup_table[i])
+			break;
+	}
+
+	if (i == 0) {
+		temp = gti->lower_temp;
+	} else if (i >= (gti->nsteps - 1)) {
+		temp = gti->upper_temp;
+	} else {
+		adc_hi = gti->lookup_table[i - 1];
+		adc_lo = gti->lookup_table[i];
+		temp = (gti->lower_temp + i * gti->step_temp);
+		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;
+	u32 range_temp;
+	int ret;
+
+	ret = of_property_read_s32(np, "lower-temperature", &gti->lower_temp);
+	if (ret < 0) {
+		dev_err(dev, "Lower temp not found\n");
+		return ret;
+	}
+
+	ret = of_property_read_s32(np, "upper-temperature", &gti->upper_temp);
+	if (ret < 0) {
+		dev_err(dev, "Upper temp not found\n");
+		return ret;
+	}
+
+	ret = of_property_read_u32(np, "step-temperature", &gti->step_temp);
+	if (ret < 0) {
+		dev_err(dev, "Steps temp not found\n");
+		return ret;
+	}
+
+	range_temp = abs(gti->upper_temp - gti->lower_temp);
+	if (range_temp % gti->step_temp) {
+		dev_err(dev, "Steps does not meet with lower/upper\n");
+		return -EINVAL;
+	}
+
+	gti->nsteps = range_temp / gti->step_temp;
+
+	gti->lookup_table = devm_kzalloc(dev, sizeof(*gti->lookup_table) *
+					 gti->nsteps, GFP_KERNEL);
+	if (!gti->lookup_table)
+		return -ENOMEM;
+
+	ret = of_property_read_u32_array(np, "temperature-lookup-table",
+					 gti->lookup_table, gti->nsteps);
+	if (ret < 0) {
+		dev_err(dev, "Failed to read temperature lookup table: %d\n",
+			ret);
+		return ret;
+	}
+
+	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 = devm_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);
+
+	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 1/2] thermal: generic-adc: Add DT binding for ADC based thermal sensor driver

[Eduardo Valentin]

On Wed, Apr 06, 2016 at 03:33:05PM +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. The ADC interface is provided
> through the IIO framework.
> 
> 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>
> ---
>  .../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..6b3e715
> --- /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. The voltage read across the sensor is mapped to temperature using
> +voltage-temperature lookup table.
> +
> +This driver provides the interface to sensor-ADC interconnection and
> +the relation ship between ADC read value and temperature.
> +
> +Required properties:
> +===================
> +- compatible:		     Must be "generic-adc-thermal".
> +- lower-temperature:	     Lower temperature for the lookup table
> +			     in millicelsius.
> +- upper-temperature:	     Upper temperature for the lookup table
> +			     in millicelsius.
> +- step-temperature:	     The temperature steps for the reading ADC
> +			     value in millicelsius.

How about when you have a sensor that does not have a nice linear
stepping correlation ?

> +- temperature-lookup-table:  The ADC reading value on each step of the
> +			     temperature starting from lower temperature
> +			     to upper temperature.
> +			     When ADC is read, the value is looked up on the
> +			     table to get the equivalent temperature.

I would say, we would need to support a two dimensional table here..

> +- #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>; 
> +	};
> +};
> +
> +thermal-sensor@1 {
> +	compatible = "generic-adc-thermal";
> +	#thermal-sensor-cells = <0>;
> +	io-channels = <&ads1015 1>; 
> +	io-channel-names = "sensor-channel";
> +	lower-temperature = <(-40000)>;
> +	upper-temperature = <125000>;
> +	step-temperature = <1000>;
> +	temperature-lookup-table = <2578 2577 2576 2575 2574
> +				2573 2572 2571 2569 2568
> +				2567 2565 2563 2561 2559
> +				::::::::::
> +				254 247 240 233 226 220 
> +				214 208>;
> +};
> +
> +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>;
> +			writable;

Not sure about writable property, where is it described?

> +		};
> +	};
> +
> +	cooling-maps {
> +		map0 {
> +			trip = <&therm_est_trip>;
> +			cooling-device = <&dummy_cool_dev THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
> +			contribution = <100>;
> +			cdev-type = "therm_est_activ";


Not sure about cdev-type property, where is it described?

> +			};
> +		};
> +
> +	};
> +};
> -- 
> 2.1.4
> 

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

[Laxman Dewangan]

Hi Eduardo,
Thanks for review.

On Wednesday 06 April 2016 09:31 PM, Eduardo Valentin wrote:
> On Wed, Apr 06, 2016 at 03:33:05PM +0530, Laxman Dewangan wrote:
>> +- step-temperature:	     The temperature steps for the reading ADC
>> +			     value in millicelsius.
> How about when you have a sensor that does not have a nice linear
> stepping correlation ?

Here just temp is stepping but ADC reading is not in linear. So temp vs 
adc value is not linear.
Just making the table that temp vs adc value where temp is in equally 
stepped.

if something is not possible for few steps than that can be intrapolate 
here to get this.

Other way as you said: two dimensional. You mean <temp ADC-value> pair 
for the table?

This is also possible and on this case, we will not need lower/upper and 
step temperature.
Table will provide all the information.

Also, I assume that sensor is negative coefficients. Temp increases->ADC 
read value decreases.

Should we also support positive coefficient relation?

> +			writable;
> Not sure about writable property, where is it described?
It is from my testing, not standard.  I will remove it.
>> +		};
>> +	};
>> +
>> +	cooling-maps {
>> +		map0 {
>> +			trip = <&therm_est_trip>;
>> +			cooling-device = <&dummy_cool_dev THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
>> +			contribution = <100>;
>> +			cdev-type = "therm_est_activ";
>
> Not sure about cdev-type property, where is it described?
 From my testing only. Will remove it.

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

[Rob Herring]

On Wed, Apr 06, 2016 at 03:33:05PM +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. The ADC interface is provided
> through the IIO framework.

IIO framework is a detail not relevant to the binding.

> 
> 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>
> ---
>  .../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..6b3e715
> --- /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. The voltage read across the sensor is mapped to temperature using
> +voltage-temperature lookup table.
> +
> +This driver provides the interface to sensor-ADC interconnection and
> +the relation ship between ADC read value and temperature.

Bindings don't describe drivers.

> +
> +Required properties:
> +===================
> +- compatible:		     Must be "generic-adc-thermal".
> +- lower-temperature:	     Lower temperature for the lookup table
> +			     in millicelsius.
> +- upper-temperature:	     Upper temperature for the lookup table
> +			     in millicelsius.
> +- step-temperature:	     The temperature steps for the reading ADC
> +			     value in millicelsius.
> +- temperature-lookup-table:  The ADC reading value on each step of the
> +			     temperature starting from lower temperature
> +			     to upper 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>; 
> +	};
> +};
> +
> +thermal-sensor@1 {
> +	compatible = "generic-adc-thermal";
> +	#thermal-sensor-cells = <0>;
> +	io-channels = <&ads1015 1>; 
> +	io-channel-names = "sensor-channel";
> +	lower-temperature = <(-40000)>;
> +	upper-temperature = <125000>;
> +	step-temperature = <1000>;
> +	temperature-lookup-table = <2578 2577 2576 2575 2574
> +				2573 2572 2571 2569 2568
> +				2567 2565 2563 2561 2559
> +				::::::::::
> +				254 247 240 233 226 220 
> +				214 208>;
> +};
> +
> +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>;

Missing a label?

> +
> +		trips {
> +			therm_est_trip: therm_est_trip {
> +			temperature = <40000>;
> +			type = "active";
> +			hysteresis = <1000>;
> +			writable;

Missing indentation and closing brace.

> +		};
> +	};
> +
> +	cooling-maps {
> +		map0 {
> +			trip = <&therm_est_trip>;
> +			cooling-device = <&dummy_cool_dev THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
> +			contribution = <100>;
> +			cdev-type = "therm_est_activ";
> +			};

Here's your missing brace... 

> +		};
> +
> +	};
> +};
> -- 
> 2.1.4
>