1 // SPDX-License-Identifier: GPL-2.0-or-later
3  * w1-uart - UART 1-Wire bus driver
5  * Uses the UART interface (via Serial Device Bus) to create the 1-Wire
6  * timing patterns. Implements the following 1-Wire master interface:
8  * - reset_bus: requests baud-rate 9600
10  * - touch_bit: requests baud-rate 115200
16 #include <linux/delay.h>
27 /* Timeout to wait for completion of serdev-receive */
31  * struct w1_uart_config - configuration for 1-Wire operation
32  * @baudrate: baud-rate returned from serdev
33  * @delay_us: delay to complete a 1-Wire cycle (in us)
34  * @tx_byte: byte to generate 1-Wire timing pattern
43  * struct w1_uart_device - 1-Wire UART device structure
45  * @bus: w1-bus master
46  * @cfg_reset: config for 1-Wire reset
47  * @cfg_touch_0: config for 1-Wire write-0 cycle
48  * @cfg_touch_1: config for 1-Wire write-1 and read cycle
51  * @rx_err: indicates an error in serdev-receive
52  * @rx_byte: result byte from serdev-receive
65 	 * w1-callbacks and serdev-receive.
73  * struct w1_uart_limits - limits for 1-Wire operations
74  * @baudrate: Requested baud-rate to create 1-Wire timing pattern
75  * @bit_min_us: minimum time for a bit (in us)
76  * @bit_max_us: maximum time for a bit (in us)
77  * @sample_us: timespan to sample 1-Wire response
78  * @cycle_us: duration of the 1-Wire cycle
93 static inline unsigned int to_ns(unsigned int us)  in to_ns()  argument
95 	return us * NSEC_PER_USEC;  in to_ns()
99  * Set baud-rate, delay and tx-byte to create a 1-Wire pulse and adapt
100  * the tx-byte according to the actual baud-rate.
103  * - time for a bit outside min/max range
104  * - a 1-Wire response is not detectable for sent byte
115 	w1cfg->baudrate = serdev_device_set_baudrate(serdev, limits->baudrate);  in w1_uart_set_config()
116 	if (w1cfg->baudrate == 0)  in w1_uart_set_config()
117 		return -EINVAL;  in w1_uart_set_config()
120 	bit_ns = baud_to_bit_ns(w1cfg->baudrate);  in w1_uart_set_config()
121 	bits_low = to_ns(limits->bit_min_us) / bit_ns;  in w1_uart_set_config()
125 	if (low_ns < to_ns(limits->bit_min_us))  in w1_uart_set_config()
126 		return -EINVAL;  in w1_uart_set_config()
128 	if (low_ns > to_ns(limits->bit_max_us))  in w1_uart_set_config()
129 		return -EINVAL;  in w1_uart_set_config()
131 	/* 1-Wire response detectable for sent byte */  in w1_uart_set_config()
132 	if (limits->sample_us > 0 &&  in w1_uart_set_config()
133 	    bit_ns * BITS_PER_BYTE < low_ns + to_ns(limits->sample_us))  in w1_uart_set_config()
134 		return -EINVAL;  in w1_uart_set_config()
136 	/* delay: 1-Wire cycle takes longer than the UART packet */  in w1_uart_set_config()
138 	w1cfg->delay_us = 0;  in w1_uart_set_config()
139 	if (to_ns(limits->cycle_us) > packet_ns)  in w1_uart_set_config()
140 		w1cfg->delay_us =  in w1_uart_set_config()
141 			(to_ns(limits->cycle_us) - packet_ns) / NSEC_PER_USEC;  in w1_uart_set_config()
143 	/* byte to create 1-Wire pulse */  in w1_uart_set_config()
144 	w1cfg->tx_byte = 0xff << bits_low;  in w1_uart_set_config()
151  * - bit_min_us is 480us, add margin and use 485us
152  * - limits for sample time 60us-75us, use 65us
156 	struct serdev_device *serdev = w1dev->serdev;  in w1_uart_set_config_reset()
157 	struct device_node *np = serdev->dev.of_node;  in w1_uart_set_config_reset()
165 	of_property_read_u32(np, "reset-bps", &limits.baudrate);  in w1_uart_set_config_reset()
167 	return w1_uart_set_config(serdev, &limits, &w1dev->cfg_reset);  in w1_uart_set_config_reset()
171  * Configuration for write-0 cycle (touch bit 0)
172  * - bit_min_us is 60us, add margin and use 65us
173  * - no sampling required, sample_us = 0
177 	struct serdev_device *serdev = w1dev->serdev;  in w1_uart_set_config_touch_0()
178 	struct device_node *np = serdev->dev.of_node;  in w1_uart_set_config_touch_0()
186 	of_property_read_u32(np, "write-0-bps", &limits.baudrate);  in w1_uart_set_config_touch_0()
188 	return w1_uart_set_config(serdev, &limits, &w1dev->cfg_touch_0);  in w1_uart_set_config_touch_0()
192  * Configuration for write-1 and read cycle (touch bit 1)
193  * - bit_min_us is 5us, add margin and use 6us
194  * - limits for sample time 5us-15us, use 15us
198 	struct serdev_device *serdev = w1dev->serdev;  in w1_uart_set_config_touch_1()
199 	struct device_node *np = serdev->dev.of_node;  in w1_uart_set_config_touch_1()
207 	of_property_read_u32(np, "write-1-bps", &limits.baudrate);  in w1_uart_set_config_touch_1()
209 	return w1_uart_set_config(serdev, &limits, &w1dev->cfg_touch_1);  in w1_uart_set_config_touch_1()
217 	struct serdev_device *serdev = w1dev->serdev;  in w1_uart_serdev_open()
218 	struct device *dev = &serdev->dev;  in w1_uart_serdev_open()
239 		dev_err(dev, "config for touch-0 failed\n");  in w1_uart_serdev_open()
245 		dev_err(dev, "config for touch-1 failed\n");  in w1_uart_serdev_open()
260 	struct serdev_device *serdev = w1dev->serdev;  in w1_uart_serdev_tx_rx()
264 	serdev_device_set_baudrate(serdev, w1cfg->baudrate);  in w1_uart_serdev_tx_rx()
267 	reinit_completion(&w1dev->rx_byte_received);  in w1_uart_serdev_tx_rx()
268 	ret = serdev_device_write_buf(serdev, &w1cfg->tx_byte, 1);  in w1_uart_serdev_tx_rx()
270 		return -EIO;  in w1_uart_serdev_tx_rx()
272 		&w1dev->rx_byte_received, W1_UART_TIMEOUT);  in w1_uart_serdev_tx_rx()
274 		return -EIO;  in w1_uart_serdev_tx_rx()
277 	if (!mutex_trylock(&w1dev->rx_mutex))  in w1_uart_serdev_tx_rx()
278 		return -EIO;  in w1_uart_serdev_tx_rx()
280 	ret = w1dev->rx_err;  in w1_uart_serdev_tx_rx()
282 		*rx_byte = w1dev->rx_byte;  in w1_uart_serdev_tx_rx()
284 	mutex_unlock(&w1dev->rx_mutex);  in w1_uart_serdev_tx_rx()
286 	if (w1cfg->delay_us > 0)  in w1_uart_serdev_tx_rx()
287 		fsleep(w1cfg->delay_us);  in w1_uart_serdev_tx_rx()
297 	mutex_lock(&w1dev->rx_mutex);  in w1_uart_serdev_receive_buf()
301 		w1dev->rx_byte = buf[0];  in w1_uart_serdev_receive_buf()
302 		w1dev->rx_err = 0;  in w1_uart_serdev_receive_buf()
304 		w1dev->rx_err = -EIO;  in w1_uart_serdev_receive_buf()
307 	mutex_unlock(&w1dev->rx_mutex);  in w1_uart_serdev_receive_buf()
308 	complete(&w1dev->rx_byte_received);  in w1_uart_serdev_receive_buf()
319  * 1-wire reset and presence detect: A present slave will manipulate
320  * the received byte by pulling the 1-Wire low.
325 	const struct w1_uart_config *w1cfg = &w1dev->cfg_reset;  in w1_uart_reset_bus()
331 		return -1;  in w1_uart_reset_bus()
334 	return val != w1cfg->tx_byte ? 0 : 1;  in w1_uart_reset_bus()
338  * 1-Wire read and write cycle: Only the read-0 manipulates the
344 	const struct w1_uart_config *w1cfg = bit ? &w1dev->cfg_touch_1 :  in w1_uart_touch_bit()
345 						   &w1dev->cfg_touch_0;  in w1_uart_touch_bit()
355 	return val == w1cfg->tx_byte ? 1 : 0;  in w1_uart_touch_bit()
360 	struct device *dev = &serdev->dev;  in w1_uart_probe()
366 		return -ENOMEM;  in w1_uart_probe()
367 	w1dev->bus.data = w1dev;  in w1_uart_probe()
368 	w1dev->bus.reset_bus = w1_uart_reset_bus;  in w1_uart_probe()
369 	w1dev->bus.touch_bit = w1_uart_touch_bit;  in w1_uart_probe()
370 	w1dev->serdev = serdev;  in w1_uart_probe()
372 	init_completion(&w1dev->rx_byte_received);  in w1_uart_probe()
373 	mutex_init(&w1dev->rx_mutex);  in w1_uart_probe()
381 	return w1_add_master_device(&w1dev->bus);  in w1_uart_probe()
389 	 * Waits until w1-uart callbacks are finished, serdev is closed  in w1_uart_remove()
391 	 * until serdev-receive is finished).  in w1_uart_remove()
393 	w1_remove_master_device(&w1dev->bus);  in w1_uart_remove()
397 	{ .compatible = "w1-uart" },
404 		.name		= "w1-uart",