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
27 struct tango_thermal_priv {
28 void __iomem *base;
29 int thresh_idx;
30 };
31
temp_above_thresh(void __iomem * base,int thresh_idx)32 static 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
tango_get_temp(void * arg,int * res)41 static 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
63 static const struct thermal_zone_of_device_ops ops = {
64 .get_temp = tango_get_temp,
65 };
66
tango_thermal_init(struct tango_thermal_priv * priv)67 static 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
tango_thermal_probe(struct platform_device * pdev)73 static 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
tango_thermal_resume(struct device * dev)96 static int __maybe_unused tango_thermal_resume(struct device *dev)
97 {
98 tango_thermal_init(dev_get_drvdata(dev));
99 return 0;
100 }
101
102 static SIMPLE_DEV_PM_OPS(tango_thermal_pm, NULL, tango_thermal_resume);
103
104 static const struct of_device_id tango_sensor_ids[] = {
105 {
106 .compatible = "sigma,smp8758-thermal",
107 },
108 { /* sentinel */ }
109 };
110 MODULE_DEVICE_TABLE(of, tango_sensor_ids);
111
112 static 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
121 module_platform_driver(tango_thermal_driver);
122
123 MODULE_LICENSE("GPL");
124 MODULE_AUTHOR("Sigma Designs");
125 MODULE_DESCRIPTION("Tango temperature sensor");
126
