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");