1// SPDX-License-Identifier: GPL-2.0-only
  2#include <linux/io.h>
  3#include <linux/delay.h>
  4#include <linux/module.h>
  5#include <linux/thermal.h>
  6#include <linux/platform_device.h>
  7
  8/*
  9 * According to a data sheet draft, "this temperature sensor uses a bandgap
 10 * type of circuit to compare a voltage which has a negative temperature
 11 * coefficient with a voltage that is proportional to absolute temperature.
 12 * A resistor bank allows 41 different temperature thresholds to be selected
 13 * and the logic output will then indicate whether the actual die temperature
 14 * lies above or below the selected threshold."
 15 */
 16
 17#define TEMPSI_CMD	0
 18#define TEMPSI_RES	4
 19#define TEMPSI_CFG	8
 20
 21#define CMD_OFF		0
 22#define CMD_ON		1
 23#define CMD_READ	2
 24
 25#define IDX_MIN		15
 26#define IDX_MAX		40
 27
 28struct tango_thermal_priv {
 29	void __iomem *base;
 30	int thresh_idx;
 31};
 32
 33static bool temp_above_thresh(void __iomem *base, int thresh_idx)
 34{
 35	writel(CMD_READ | thresh_idx << 8, base + TEMPSI_CMD);
 36	usleep_range(10, 20);
 37	writel(CMD_READ | thresh_idx << 8, base + TEMPSI_CMD);
 38
 39	return readl(base + TEMPSI_RES);
 40}
 41
 42static int tango_get_temp(void *arg, int *res)
 43{
 44	struct tango_thermal_priv *priv = arg;
 45	int idx = priv->thresh_idx;
 46
 47	if (temp_above_thresh(priv->base, idx)) {
 48		/* Search upward by incrementing thresh_idx */
 49		while (idx < IDX_MAX && temp_above_thresh(priv->base, ++idx))
 50			cpu_relax();
 51		idx = idx - 1; /* always return lower bound */
 52	} else {
 53		/* Search downward by decrementing thresh_idx */
 54		while (idx > IDX_MIN && !temp_above_thresh(priv->base, --idx))
 55			cpu_relax();
 56	}
 57
 58	*res = (idx * 9 / 2 - 38) * 1000; /* millidegrees Celsius */
 59	priv->thresh_idx = idx;
 60
 61	return 0;
 62}
 63
 64static const struct thermal_zone_of_device_ops ops = {
 65	.get_temp	= tango_get_temp,
 66};
 67
 68static void tango_thermal_init(struct tango_thermal_priv *priv)
 69{
 70	writel(0, priv->base + TEMPSI_CFG);
 71	writel(CMD_ON, priv->base + TEMPSI_CMD);
 72}
 73
 74static int tango_thermal_probe(struct platform_device *pdev)
 75{
 76	struct resource *res;
 77	struct tango_thermal_priv *priv;
 78	struct thermal_zone_device *tzdev;
 79
 80	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
 81	if (!priv)
 82		return -ENOMEM;
 83
 84	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 85	priv->base = devm_ioremap_resource(&pdev->dev, res);
 86	if (IS_ERR(priv->base))
 87		return PTR_ERR(priv->base);
 88
 89	platform_set_drvdata(pdev, priv);
 90	priv->thresh_idx = IDX_MIN;
 91	tango_thermal_init(priv);
 92
 93	tzdev = devm_thermal_zone_of_sensor_register(&pdev->dev, 0, priv, &ops);
 94	return PTR_ERR_OR_ZERO(tzdev);
 95}
 96
 97static int __maybe_unused tango_thermal_resume(struct device *dev)
 98{
 99	tango_thermal_init(dev_get_drvdata(dev));
100	return 0;
101}
102
103static SIMPLE_DEV_PM_OPS(tango_thermal_pm, NULL, tango_thermal_resume);
104
105static const struct of_device_id tango_sensor_ids[] = {
106	{
107		.compatible = "sigma,smp8758-thermal",
108	},
109	{ /* sentinel */ }
110};
111MODULE_DEVICE_TABLE(of, tango_sensor_ids);
112
113static struct platform_driver tango_thermal_driver = {
114	.probe	= tango_thermal_probe,
115	.driver	= {
116		.name		= "tango-thermal",
117		.of_match_table	= tango_sensor_ids,
118		.pm		= &tango_thermal_pm,
119	},
120};
121
122module_platform_driver(tango_thermal_driver);
123
124MODULE_LICENSE("GPL");
125MODULE_AUTHOR("Sigma Designs");
126MODULE_DESCRIPTION("Tango temperature sensor");