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
28 struct tango_thermal_priv {
29 void __iomem *base;
30 int thresh_idx;
31 };
32
temp_above_thresh(void __iomem * base,int thresh_idx)33 static 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
tango_get_temp(void * arg,int * res)42 static 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
64 static const struct thermal_zone_of_device_ops ops = {
65 .get_temp = tango_get_temp,
66 };
67
tango_thermal_init(struct tango_thermal_priv * priv)68 static 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
tango_thermal_probe(struct platform_device * pdev)74 static 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
tango_thermal_resume(struct device * dev)97 static int __maybe_unused tango_thermal_resume(struct device *dev)
98 {
99 tango_thermal_init(dev_get_drvdata(dev));
100 return 0;
101 }
102
103 static SIMPLE_DEV_PM_OPS(tango_thermal_pm, NULL, tango_thermal_resume);
104
105 static const struct of_device_id tango_sensor_ids[] = {
106 {
107 .compatible = "sigma,smp8758-thermal",
108 },
109 { /* sentinel */ }
110 };
111 MODULE_DEVICE_TABLE(of, tango_sensor_ids);
112
113 static 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
122 module_platform_driver(tango_thermal_driver);
123
124 MODULE_LICENSE("GPL");
125 MODULE_AUTHOR("Sigma Designs");
126 MODULE_DESCRIPTION("Tango temperature sensor");
127