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0b58c08b MG |
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 | ||
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 | ||
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 | ||
67 | static 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; | |
431c30f7 | 83 | writel(0, priv->base + TEMPSI_CFG); |
0b58c08b MG |
84 | writel(CMD_ON, priv->base + TEMPSI_CMD); |
85 | ||
86 | tzdev = devm_thermal_zone_of_sensor_register(&pdev->dev, 0, priv, &ops); | |
bba07c13 | 87 | return PTR_ERR_OR_ZERO(tzdev); |
0b58c08b MG |
88 | } |
89 | ||
90 | static const struct of_device_id tango_sensor_ids[] = { | |
91 | { | |
92 | .compatible = "sigma,smp8758-thermal", | |
93 | }, | |
94 | { /* sentinel */ } | |
95 | }; | |
96 | ||
97 | static 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 | ||
105 | module_platform_driver(tango_thermal_driver); | |
106 | ||
107 | MODULE_LICENSE("GPL"); | |
108 | MODULE_AUTHOR("Sigma Designs"); | |
109 | MODULE_DESCRIPTION("Tango temperature sensor"); |