tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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 int tango_thermal_probe(struct platform_device *pdev)
68{
69 struct resource *res;
70 struct tango_thermal_priv *priv;
71 struct thermal_zone_device *tzdev;
72
73 priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
74 if (!priv)
75 return -ENOMEM;
76
77 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
78 priv->base = devm_ioremap_resource(&pdev->dev, res);
79 if (IS_ERR(priv->base))
80 return PTR_ERR(priv->base);
81
82 priv->thresh_idx = IDX_MIN;
83 writel(0, priv->base + TEMPSI_CFG);
84 writel(CMD_ON, priv->base + TEMPSI_CMD);
85
86 tzdev = devm_thermal_zone_of_sensor_register(&pdev->dev, 0, priv, &ops);
87 return PTR_ERR_OR_ZERO(tzdev);
88}
89
90static const struct of_device_id tango_sensor_ids[] = {
91 {
92 .compatible = "sigma,smp8758-thermal",
93 },
94 { /* sentinel */ }
95};
96
97static struct platform_driver tango_thermal_driver = {
98 .probe = tango_thermal_probe,
99 .driver = {
100 .name = "tango-thermal",
101 .of_match_table = tango_sensor_ids,
102 },
103};
104
105module_platform_driver(tango_thermal_driver);
106
107MODULE_LICENSE("GPL");
108MODULE_AUTHOR("Sigma Designs");
109MODULE_DESCRIPTION("Tango temperature sensor");