1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Driver for Broadcom BCM2835 SoC temperature sensor
4  *
5  * Copyright (C) 2016 Martin Sperl
6  */
7 
8 #include <linux/clk.h>
9 #include <linux/debugfs.h>
10 #include <linux/device.h>
11 #include <linux/err.h>
12 #include <linux/io.h>
13 #include <linux/kernel.h>
14 #include <linux/module.h>
15 #include <linux/of.h>
16 #include <linux/of_address.h>
17 #include <linux/of_device.h>
18 #include <linux/platform_device.h>
19 #include <linux/thermal.h>
20 
21 #define BCM2835_TS_TSENSCTL			0x00
22 #define BCM2835_TS_TSENSSTAT			0x04
23 
24 #define BCM2835_TS_TSENSCTL_PRWDW		BIT(0)
25 #define BCM2835_TS_TSENSCTL_RSTB		BIT(1)
26 
27 /*
28  * bandgap reference voltage in 6 mV increments
29  * 000b = 1178 mV, 001b = 1184 mV, ... 111b = 1220 mV
30  */
31 #define BCM2835_TS_TSENSCTL_CTRL_BITS		3
32 #define BCM2835_TS_TSENSCTL_CTRL_SHIFT		2
33 #define BCM2835_TS_TSENSCTL_CTRL_MASK		    \
34 	GENMASK(BCM2835_TS_TSENSCTL_CTRL_BITS +     \
35 		BCM2835_TS_TSENSCTL_CTRL_SHIFT - 1, \
36 		BCM2835_TS_TSENSCTL_CTRL_SHIFT)
37 #define BCM2835_TS_TSENSCTL_CTRL_DEFAULT	1
38 #define BCM2835_TS_TSENSCTL_EN_INT		BIT(5)
39 #define BCM2835_TS_TSENSCTL_DIRECT		BIT(6)
40 #define BCM2835_TS_TSENSCTL_CLR_INT		BIT(7)
41 #define BCM2835_TS_TSENSCTL_THOLD_SHIFT		8
42 #define BCM2835_TS_TSENSCTL_THOLD_BITS		10
43 #define BCM2835_TS_TSENSCTL_THOLD_MASK		     \
44 	GENMASK(BCM2835_TS_TSENSCTL_THOLD_BITS +     \
45 		BCM2835_TS_TSENSCTL_THOLD_SHIFT - 1, \
46 		BCM2835_TS_TSENSCTL_THOLD_SHIFT)
47 /*
48  * time how long the block to be asserted in reset
49  * which based on a clock counter (TSENS clock assumed)
50  */
51 #define BCM2835_TS_TSENSCTL_RSTDELAY_SHIFT	18
52 #define BCM2835_TS_TSENSCTL_RSTDELAY_BITS	8
53 #define BCM2835_TS_TSENSCTL_REGULEN		BIT(26)
54 
55 #define BCM2835_TS_TSENSSTAT_DATA_BITS		10
56 #define BCM2835_TS_TSENSSTAT_DATA_SHIFT		0
57 #define BCM2835_TS_TSENSSTAT_DATA_MASK		     \
58 	GENMASK(BCM2835_TS_TSENSSTAT_DATA_BITS +     \
59 		BCM2835_TS_TSENSSTAT_DATA_SHIFT - 1, \
60 		BCM2835_TS_TSENSSTAT_DATA_SHIFT)
61 #define BCM2835_TS_TSENSSTAT_VALID		BIT(10)
62 #define BCM2835_TS_TSENSSTAT_INTERRUPT		BIT(11)
63 
64 struct bcm2835_thermal_data {
65 	struct thermal_zone_device *tz;
66 	void __iomem *regs;
67 	struct clk *clk;
68 	struct dentry *debugfsdir;
69 };
70 
71 static int bcm2835_thermal_adc2temp(u32 adc, int offset, int slope)
72 {
73 	return offset + slope * adc;
74 }
75 
76 static int bcm2835_thermal_temp2adc(int temp, int offset, int slope)
77 {
78 	temp -= offset;
79 	temp /= slope;
80 
81 	if (temp < 0)
82 		temp = 0;
83 	if (temp >= BIT(BCM2835_TS_TSENSSTAT_DATA_BITS))
84 		temp = BIT(BCM2835_TS_TSENSSTAT_DATA_BITS) - 1;
85 
86 	return temp;
87 }
88 
89 static int bcm2835_thermal_get_temp(void *d, int *temp)
90 {
91 	struct bcm2835_thermal_data *data = d;
92 	u32 val = readl(data->regs + BCM2835_TS_TSENSSTAT);
93 
94 	if (!(val & BCM2835_TS_TSENSSTAT_VALID))
95 		return -EIO;
96 
97 	val &= BCM2835_TS_TSENSSTAT_DATA_MASK;
98 
99 	*temp = bcm2835_thermal_adc2temp(
100 		val,
101 		thermal_zone_get_offset(data->tz),
102 		thermal_zone_get_slope(data->tz));
103 
104 	return 0;
105 }
106 
107 static const struct debugfs_reg32 bcm2835_thermal_regs[] = {
108 	{
109 		.name = "ctl",
110 		.offset = 0
111 	},
112 	{
113 		.name = "stat",
114 		.offset = 4
115 	}
116 };
117 
118 static void bcm2835_thermal_debugfs(struct platform_device *pdev)
119 {
120 	struct thermal_zone_device *tz = platform_get_drvdata(pdev);
121 	struct bcm2835_thermal_data *data = tz->devdata;
122 	struct debugfs_regset32 *regset;
123 
124 	data->debugfsdir = debugfs_create_dir("bcm2835_thermal", NULL);
125 	if (!data->debugfsdir)
126 		return;
127 
128 	regset = devm_kzalloc(&pdev->dev, sizeof(*regset), GFP_KERNEL);
129 	if (!regset)
130 		return;
131 
132 	regset->regs = bcm2835_thermal_regs;
133 	regset->nregs = ARRAY_SIZE(bcm2835_thermal_regs);
134 	regset->base = data->regs;
135 
136 	debugfs_create_regset32("regset", 0444, data->debugfsdir, regset);
137 }
138 
139 static const struct thermal_zone_of_device_ops bcm2835_thermal_ops = {
140 	.get_temp = bcm2835_thermal_get_temp,
141 };
142 
143 /*
144  * Note: as per Raspberry Foundation FAQ
145  * (https://www.raspberrypi.org/help/faqs/#performanceOperatingTemperature)
146  * the recommended temperature range for the SoC -40C to +85C
147  * so the trip limit is set to 80C.
148  * this applies to all the BCM283X SoC
149  */
150 
151 static const struct of_device_id bcm2835_thermal_of_match_table[] = {
152 	{
153 		.compatible = "brcm,bcm2835-thermal",
154 	},
155 	{
156 		.compatible = "brcm,bcm2836-thermal",
157 	},
158 	{
159 		.compatible = "brcm,bcm2837-thermal",
160 	},
161 	{},
162 };
163 MODULE_DEVICE_TABLE(of, bcm2835_thermal_of_match_table);
164 
165 static int bcm2835_thermal_probe(struct platform_device *pdev)
166 {
167 	const struct of_device_id *match;
168 	struct thermal_zone_device *tz;
169 	struct bcm2835_thermal_data *data;
170 	struct resource *res;
171 	int err = 0;
172 	u32 val;
173 	unsigned long rate;
174 
175 	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
176 	if (!data)
177 		return -ENOMEM;
178 
179 	match = of_match_device(bcm2835_thermal_of_match_table,
180 				&pdev->dev);
181 	if (!match)
182 		return -EINVAL;
183 
184 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
185 	data->regs = devm_ioremap_resource(&pdev->dev, res);
186 	if (IS_ERR(data->regs)) {
187 		err = PTR_ERR(data->regs);
188 		dev_err(&pdev->dev, "Could not get registers: %d\n", err);
189 		return err;
190 	}
191 
192 	data->clk = devm_clk_get(&pdev->dev, NULL);
193 	if (IS_ERR(data->clk)) {
194 		err = PTR_ERR(data->clk);
195 		if (err != -EPROBE_DEFER)
196 			dev_err(&pdev->dev, "Could not get clk: %d\n", err);
197 		return err;
198 	}
199 
200 	err = clk_prepare_enable(data->clk);
201 	if (err)
202 		return err;
203 
204 	rate = clk_get_rate(data->clk);
205 	if ((rate < 1920000) || (rate > 5000000))
206 		dev_warn(&pdev->dev,
207 			 "Clock %pCn running at %lu Hz is outside of the recommended range: 1.92 to 5MHz\n",
208 			 data->clk, rate);
209 
210 	/* register of thermal sensor and get info from DT */
211 	tz = thermal_zone_of_sensor_register(&pdev->dev, 0, data,
212 					     &bcm2835_thermal_ops);
213 	if (IS_ERR(tz)) {
214 		err = PTR_ERR(tz);
215 		dev_err(&pdev->dev,
216 			"Failed to register the thermal device: %d\n",
217 			err);
218 		goto err_clk;
219 	}
220 
221 	/*
222 	 * right now the FW does set up the HW-block, so we are not
223 	 * touching the configuration registers.
224 	 * But if the HW is not enabled, then set it up
225 	 * using "sane" values used by the firmware right now.
226 	 */
227 	val = readl(data->regs + BCM2835_TS_TSENSCTL);
228 	if (!(val & BCM2835_TS_TSENSCTL_RSTB)) {
229 		int trip_temp, offset, slope;
230 
231 		slope = thermal_zone_get_slope(tz);
232 		offset = thermal_zone_get_offset(tz);
233 		/*
234 		 * For now we deal only with critical, otherwise
235 		 * would need to iterate
236 		 */
237 		err = tz->ops->get_trip_temp(tz, 0, &trip_temp);
238 		if (err < 0) {
239 			dev_err(&pdev->dev,
240 				"Not able to read trip_temp: %d\n",
241 				err);
242 			goto err_tz;
243 		}
244 
245 		/* set bandgap reference voltage and enable voltage regulator */
246 		val = (BCM2835_TS_TSENSCTL_CTRL_DEFAULT <<
247 		       BCM2835_TS_TSENSCTL_CTRL_SHIFT) |
248 		      BCM2835_TS_TSENSCTL_REGULEN;
249 
250 		/* use the recommended reset duration */
251 		val |= (0xFE << BCM2835_TS_TSENSCTL_RSTDELAY_SHIFT);
252 
253 		/*  trip_adc value from info */
254 		val |= bcm2835_thermal_temp2adc(trip_temp,
255 						offset,
256 						slope)
257 			<< BCM2835_TS_TSENSCTL_THOLD_SHIFT;
258 
259 		/* write the value back to the register as 2 steps */
260 		writel(val, data->regs + BCM2835_TS_TSENSCTL);
261 		val |= BCM2835_TS_TSENSCTL_RSTB;
262 		writel(val, data->regs + BCM2835_TS_TSENSCTL);
263 	}
264 
265 	data->tz = tz;
266 
267 	platform_set_drvdata(pdev, tz);
268 
269 	bcm2835_thermal_debugfs(pdev);
270 
271 	return 0;
272 err_tz:
273 	thermal_zone_of_sensor_unregister(&pdev->dev, tz);
274 err_clk:
275 	clk_disable_unprepare(data->clk);
276 
277 	return err;
278 }
279 
280 static int bcm2835_thermal_remove(struct platform_device *pdev)
281 {
282 	struct thermal_zone_device *tz = platform_get_drvdata(pdev);
283 	struct bcm2835_thermal_data *data = tz->devdata;
284 
285 	debugfs_remove_recursive(data->debugfsdir);
286 	thermal_zone_of_sensor_unregister(&pdev->dev, tz);
287 	clk_disable_unprepare(data->clk);
288 
289 	return 0;
290 }
291 
292 static struct platform_driver bcm2835_thermal_driver = {
293 	.probe = bcm2835_thermal_probe,
294 	.remove = bcm2835_thermal_remove,
295 	.driver = {
296 		.name = "bcm2835_thermal",
297 		.of_match_table = bcm2835_thermal_of_match_table,
298 	},
299 };
300 module_platform_driver(bcm2835_thermal_driver);
301 
302 MODULE_AUTHOR("Martin Sperl");
303 MODULE_DESCRIPTION("Thermal driver for bcm2835 chip");
304 MODULE_LICENSE("GPL");
305