1 // SPDX-License-Identifier: GPL-2.0-or-later
3  * DHT11/DHT22 bit banging GPIO driver
46  * 0-bit: 22-30uS -- typically 26uS (AM2302)
47  * 1-bit: 68-75uS -- typically 70uS (AM2302)
52  * timeres > 34uS ... don't know what a 1-tick pulse is
54  * 30uS > timeres > 23uS ... don't know what a 2-tick pulse is
57  * Luckily clocks in the 33-44kHz range are quite uncommon, so we can
58  * support most systems if the threshold for decoding a pulse as 1-bit
85 	/* num_edges: -1 means "no transmission in progress" */
99 	dev_dbg(dht11->dev, "%d edges detected:\n", dht11->num_edges);  in dht11_edges_print()
100 	for (i = 1; i < dht11->num_edges; ++i) {  in dht11_edges_print()
101 		dev_dbg(dht11->dev, "%d: %lld ns %s\n", i,  in dht11_edges_print()
102 			dht11->edges[i].ts - dht11->edges[i - 1].ts,  in dht11_edges_print()
103 			dht11->edges[i - 1].value ? "high" : "low");  in dht11_edges_print()
129 		t = dht11->edges[offset + 2 * i + 2].ts -  in dht11_decode()
130 			dht11->edges[offset + 2 * i + 1].ts;  in dht11_decode()
131 		if (!dht11->edges[offset + 2 * i + 1].value) {  in dht11_decode()
132 			dev_dbg(dht11->dev,  in dht11_decode()
135 			return -EIO;  in dht11_decode()
147 		dev_dbg(dht11->dev, "invalid checksum\n");  in dht11_decode()
148 		return -EIO;  in dht11_decode()
151 	dht11->timestamp = ktime_get_boottime_ns();  in dht11_decode()
153 		dht11->temperature = (((temp_int & 0x7f) << 8) + temp_dec) *  in dht11_decode()
154 					((temp_int & 0x80) ? -100 : 100);  in dht11_decode()
155 		dht11->humidity = ((hum_int << 8) + hum_dec) * 100;  in dht11_decode()
157 		dht11->temperature = temp_int * 1000;  in dht11_decode()
158 		dht11->humidity = hum_int * 1000;  in dht11_decode()
160 		dev_err(dht11->dev,  in dht11_decode()
163 		return -EIO;  in dht11_decode()
177 	if (dht11->num_edges < DHT11_EDGES_PER_READ && dht11->num_edges >= 0) {  in dht11_handle_irq()
178 		dht11->edges[dht11->num_edges].ts = ktime_get_boottime_ns();  in dht11_handle_irq()
179 		dht11->edges[dht11->num_edges++].value =  in dht11_handle_irq()
180 						gpiod_get_value(dht11->gpiod);  in dht11_handle_irq()
182 		if (dht11->num_edges >= DHT11_EDGES_PER_READ)  in dht11_handle_irq()
183 			complete(&dht11->completion);  in dht11_handle_irq()
196 	mutex_lock(&dht11->lock);  in dht11_read_raw()
197 	if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_boottime_ns()) {  in dht11_read_raw()
199 		dev_dbg(dht11->dev, "current timeresolution: %dns\n", timeres);  in dht11_read_raw()
201 			dev_err(dht11->dev, "timeresolution %dns too low\n",  in dht11_read_raw()
207 			ret = -EAGAIN;  in dht11_read_raw()
211 			dev_warn(dht11->dev,  in dht11_read_raw()
212 				 "timeresolution: %dns - decoding ambiguous\n",  in dht11_read_raw()
215 		reinit_completion(&dht11->completion);  in dht11_read_raw()
217 		dht11->num_edges = 0;  in dht11_read_raw()
218 		ret = gpiod_direction_output(dht11->gpiod, 0);  in dht11_read_raw()
223 		ret = gpiod_direction_input(dht11->gpiod);  in dht11_read_raw()
227 		ret = request_irq(dht11->irq, dht11_handle_irq,  in dht11_read_raw()
229 				  iio_dev->name, iio_dev);  in dht11_read_raw()
233 		ret = wait_for_completion_killable_timeout(&dht11->completion,  in dht11_read_raw()
236 		free_irq(dht11->irq, iio_dev);  in dht11_read_raw()
242 		if (ret == 0 && dht11->num_edges < DHT11_EDGES_PER_READ - 1) {  in dht11_read_raw()
243 			dev_err(dht11->dev, "Only %d signal edges detected\n",  in dht11_read_raw()
244 				dht11->num_edges);  in dht11_read_raw()
245 			ret = -ETIMEDOUT;  in dht11_read_raw()
251 				dht11->num_edges - DHT11_EDGES_PER_READ;  in dht11_read_raw()
252 		for (; offset >= 0; --offset) {  in dht11_read_raw()
263 	if (chan->type == IIO_TEMP)  in dht11_read_raw()
264 		*val = dht11->temperature;  in dht11_read_raw()
265 	else if (chan->type == IIO_HUMIDITYRELATIVE)  in dht11_read_raw()
266 		*val = dht11->humidity;  in dht11_read_raw()
268 		ret = -EINVAL;  in dht11_read_raw()
270 	dht11->num_edges = -1;  in dht11_read_raw()
271 	mutex_unlock(&dht11->lock);  in dht11_read_raw()
281 		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), },
283 		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), }
294 	struct device *dev = &pdev->dev;  in dht11_probe()
301 		return -ENOMEM;  in dht11_probe()
305 	dht11->dev = dev;  in dht11_probe()
306 	dht11->gpiod = devm_gpiod_get(dev, NULL, GPIOD_IN);  in dht11_probe()
307 	if (IS_ERR(dht11->gpiod))  in dht11_probe()
308 		return PTR_ERR(dht11->gpiod);  in dht11_probe()
310 	dht11->irq = gpiod_to_irq(dht11->gpiod);  in dht11_probe()
311 	if (dht11->irq < 0) {  in dht11_probe()
312 		dev_err(dev, "GPIO %d has no interrupt\n", desc_to_gpio(dht11->gpiod));  in dht11_probe()
313 		return -EINVAL;  in dht11_probe()
316 	dht11->timestamp = ktime_get_boottime_ns() - DHT11_DATA_VALID_TIME - 1;  in dht11_probe()
317 	dht11->num_edges = -1;  in dht11_probe()
321 	init_completion(&dht11->completion);  in dht11_probe()
322 	mutex_init(&dht11->lock);  in dht11_probe()
323 	iio->name = pdev->name;  in dht11_probe()
324 	iio->info = &dht11_iio_info;  in dht11_probe()
325 	iio->modes = INDIO_DIRECT_MODE;  in dht11_probe()
326 	iio->channels = dht11_chan_spec;  in dht11_probe()
327 	iio->num_channels = ARRAY_SIZE(dht11_chan_spec);  in dht11_probe()