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// SPDX-License-Identifier: GPL-2.0-only
/*
* Generic ADC thermal driver
*
* Copyright (C) 2016 NVIDIA CORPORATION. All rights reserved.
*
* Author: Laxman Dewangan <ldewangan@nvidia.com>
*/
#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, temp_hi, temp_lo, adc_hi, adc_lo;
int i;
if (!gti->lookup_table)
return val;
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) {
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_hi = gti->lookup_table[2 * i - 2];
temp_lo = gti->lookup_table[2 * i];
temp = temp_hi + mult_frac(temp_lo - temp_hi, val - adc_hi,
adc_lo - adc_hi);
}
return temp;
}
static int gadc_thermal_get_temp(struct thermal_zone_device *tz, int *temp)
{
struct gadc_thermal_info *gti = tz->devdata;
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_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;
enum iio_chan_type chan_type;
int ntable;
int ret;
ntable = of_property_count_elems_of_size(np, "temperature-lookup-table",
sizeof(u32));
if (ntable <= 0) {
ret = iio_get_channel_type(gti->channel, &chan_type);
if (ret || chan_type != IIO_TEMP)
dev_notice(dev,
"no lookup table, assuming DAC channel returns milliCelcius\n");
return 0;
}
if (ntable % 2) {
dev_err(dev, "Pair of temperature vs ADC read value missing\n");
return -EINVAL;
}
gti->lookup_table = devm_kcalloc(dev,
ntable, sizeof(*gti->lookup_table),
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;
gti->channel = devm_iio_channel_get(&pdev->dev, "sensor-channel");
if (IS_ERR(gti->channel)) {
ret = PTR_ERR(gti->channel);
if (ret != -EPROBE_DEFER)
dev_err(&pdev->dev, "IIO channel not found: %d\n", ret);
return ret;
}
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->tz_dev = devm_thermal_of_zone_register(&pdev->dev, 0, gti,
&gadc_thermal_ops);
if (IS_ERR(gti->tz_dev)) {
ret = PTR_ERR(gti->tz_dev);
if (ret != -EPROBE_DEFER)
dev_err(&pdev->dev,
"Thermal zone sensor register failed: %d\n",
ret);
return ret;
}
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,
};
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");
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