On 19/04/16 08:22, Laxman Dewangan wrote:
> In some of platform, thermal sensors like NCT thermistors are
> connected to the one of ADC channel. The temperature is read by
> reading the voltage across the sensor resistance via ADC. Lookup
> table for ADC read value to temperature is referred to get
> temperature. ADC is read via IIO framework.
>
> Add support for thermal sensor driver which read the voltage across
> sensor resistance from ADC through IIO framework.
>
> Signed-off-by: Laxman Dewangan <ldewangan@xxxxxxxxxx>
Acked-by: Jonathan Cameron <jic23@xxxxxxxxxx> primarily for the IIO
side of things.
>
> ---
> 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.
>
> Changes from V2:
> - None.
>
> Changes from V3:
> - Jonathan suggested to use the iio_channel_read_processed only. Making
> changes accordingly.
> ---
> drivers/thermal/Kconfig | 10 ++
> drivers/thermal/Makefile | 1 +
> drivers/thermal/thermal-generic-adc.c | 182 ++++++++++++++++++++++++++++++++++
> 3 files changed, 193 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..73f55d6
> --- /dev/null
> +++ b/drivers/thermal/thermal-generic-adc.c
> @@ -0,0 +1,182 @@
> +/*
> + * Generic ADC thermal driver
> + *
> + * Copyright (C) 2016 NVIDIA CORPORATION. All rights reserved.
> + *
> + * Author: Laxman Dewangan <ldewangan@xxxxxxxxxx>
> + *
> + * 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_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 = iio_read_channel_processed(gti->channel, &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@xxxxxxxxxx>");
> +MODULE_DESCRIPTION("Generic ADC thermal driver using IIO framework with DT");
> +MODULE_LICENSE("GPL v2");
>
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