LXR linux/drivers/thermal/tango

   1#include <linux/io.h>
   2#include <linux/delay.h>
   3#include <linux/module.h>
   4#include <linux/thermal.h>
   5#include <linux/platform_device.h>
   6
   7/*
   8 * According to a data sheet draft, "this temperature sensor uses a bandgap
   9 * type of circuit to compare a voltage which has a negative temperature
  10 * coefficient with a voltage that is proportional to absolute temperature.
  11 * A resistor bank allows 41 different temperature thresholds to be selected
  12 * and the logic output will then indicate whether the actual die temperature
  13 * lies above or below the selected threshold."
  14 */
  15
  16#define TEMPSI_CMD      0
  17#define TEMPSI_RES      4
  18#define TEMPSI_CFG      8
  19
  20#define CMD_OFF         0
  21#define CMD_ON          1
  22#define CMD_READ        2
  23
  24#define IDX_MIN         15
  25#define IDX_MAX         40
  26
  27struct tango_thermal_priv {
  28        void __iomem *base;
  29        int thresh_idx;
  30};
  31
  32static bool temp_above_thresh(void __iomem *base, int thresh_idx)
  33{
  34        writel(CMD_READ | thresh_idx << 8, base + TEMPSI_CMD);
  35        usleep_range(10, 20);
  36        writel(CMD_READ | thresh_idx << 8, base + TEMPSI_CMD);
  37
  38        return readl(base + TEMPSI_RES);
  39}
  40
  41static int tango_get_temp(void *arg, int *res)
  42{
  43        struct tango_thermal_priv *priv = arg;
  44        int idx = priv->thresh_idx;
  45
  46        if (temp_above_thresh(priv->base, idx)) {
  47                /* Search upward by incrementing thresh_idx */
  48                while (idx < IDX_MAX && temp_above_thresh(priv->base, ++idx))
  49                        cpu_relax();
  50                idx = idx - 1; /* always return lower bound */
  51        } else {
  52                /* Search downward by decrementing thresh_idx */
  53                while (idx > IDX_MIN && !temp_above_thresh(priv->base, --idx))
  54                        cpu_relax();
  55        }
  56
  57        *res = (idx * 9 / 2 - 38) * 1000; /* millidegrees Celsius */
  58        priv->thresh_idx = idx;
  59
  60        return 0;
  61}
  62
  63static const struct thermal_zone_of_device_ops ops = {
  64        .get_temp       = tango_get_temp,
  65};
  66
  67static void tango_thermal_init(struct tango_thermal_priv *priv)
  68{
  69        writel(0, priv->base + TEMPSI_CFG);
  70        writel(CMD_ON, priv->base + TEMPSI_CMD);
  71}
  72
  73static int tango_thermal_probe(struct platform_device *pdev)
  74{
  75        struct resource *res;
  76        struct tango_thermal_priv *priv;
  77        struct thermal_zone_device *tzdev;
  78
  79        priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
  80        if (!priv)
  81                return -ENOMEM;
  82
  83        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  84        priv->base = devm_ioremap_resource(&pdev->dev, res);
  85        if (IS_ERR(priv->base))
  86                return PTR_ERR(priv->base);
  87
  88        platform_set_drvdata(pdev, priv);
  89        priv->thresh_idx = IDX_MIN;
  90        tango_thermal_init(priv);
  91
  92        tzdev = devm_thermal_zone_of_sensor_register(&pdev->dev, 0, priv, &ops);
  93        return PTR_ERR_OR_ZERO(tzdev);
  94}
  95
  96static int __maybe_unused tango_thermal_resume(struct device *dev)
  97{
  98        tango_thermal_init(dev_get_drvdata(dev));
  99        return 0;
 100}
 101
 102static SIMPLE_DEV_PM_OPS(tango_thermal_pm, NULL, tango_thermal_resume);
 103
 104static const struct of_device_id tango_sensor_ids[] = {
 105        {
 106                .compatible = "sigma,smp8758-thermal",
 107        },
 108        { /* sentinel */ }
 109};
 110MODULE_DEVICE_TABLE(of, tango_sensor_ids);
 111
 112static struct platform_driver tango_thermal_driver = {
 113        .probe  = tango_thermal_probe,
 114        .driver = {
 115                .name           = "tango-thermal",
 116                .of_match_table = tango_sensor_ids,
 117                .pm             = &tango_thermal_pm,
 118        },
 119};
 120
 121module_platform_driver(tango_thermal_driver);
 122
 123MODULE_LICENSE("GPL");
 124MODULE_AUTHOR("Sigma Designs");
 125MODULE_DESCRIPTION("Tango temperature sensor");
 126