xref: /openbmc/linux/drivers/bus/ts-nbus.c (revision 3bb16560)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * NBUS driver for TS-4600 based boards
4  *
5  * Copyright (c) 2016 - Savoir-faire Linux
6  * Author: Sebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com>
7  *
8  * This driver implements a GPIOs bit-banged bus, called the NBUS by Technologic
9  * Systems. It is used to communicate with the peripherals in the FPGA on the
10  * TS-4600 SoM.
11  */
12 
13 #include <linux/bitops.h>
14 #include <linux/gpio/consumer.h>
15 #include <linux/kernel.h>
16 #include <linux/module.h>
17 #include <linux/mutex.h>
18 #include <linux/of_platform.h>
19 #include <linux/platform_device.h>
20 #include <linux/pwm.h>
21 #include <linux/ts-nbus.h>
22 
23 #define TS_NBUS_DIRECTION_IN  0
24 #define TS_NBUS_DIRECTION_OUT 1
25 #define TS_NBUS_WRITE_ADR 0
26 #define TS_NBUS_WRITE_VAL 1
27 
28 struct ts_nbus {
29 	struct pwm_device *pwm;
30 	struct gpio_descs *data;
31 	struct gpio_desc *csn;
32 	struct gpio_desc *txrx;
33 	struct gpio_desc *strobe;
34 	struct gpio_desc *ale;
35 	struct gpio_desc *rdy;
36 	struct mutex lock;
37 };
38 
39 /*
40  * request all gpios required by the bus.
41  */
ts_nbus_init_pdata(struct platform_device * pdev,struct ts_nbus * ts_nbus)42 static int ts_nbus_init_pdata(struct platform_device *pdev, struct ts_nbus
43 		*ts_nbus)
44 {
45 	ts_nbus->data = devm_gpiod_get_array(&pdev->dev, "ts,data",
46 			GPIOD_OUT_HIGH);
47 	if (IS_ERR(ts_nbus->data)) {
48 		dev_err(&pdev->dev, "failed to retrieve ts,data-gpio from dts\n");
49 		return PTR_ERR(ts_nbus->data);
50 	}
51 
52 	ts_nbus->csn = devm_gpiod_get(&pdev->dev, "ts,csn", GPIOD_OUT_HIGH);
53 	if (IS_ERR(ts_nbus->csn)) {
54 		dev_err(&pdev->dev, "failed to retrieve ts,csn-gpio from dts\n");
55 		return PTR_ERR(ts_nbus->csn);
56 	}
57 
58 	ts_nbus->txrx = devm_gpiod_get(&pdev->dev, "ts,txrx", GPIOD_OUT_HIGH);
59 	if (IS_ERR(ts_nbus->txrx)) {
60 		dev_err(&pdev->dev, "failed to retrieve ts,txrx-gpio from dts\n");
61 		return PTR_ERR(ts_nbus->txrx);
62 	}
63 
64 	ts_nbus->strobe = devm_gpiod_get(&pdev->dev, "ts,strobe", GPIOD_OUT_HIGH);
65 	if (IS_ERR(ts_nbus->strobe)) {
66 		dev_err(&pdev->dev, "failed to retrieve ts,strobe-gpio from dts\n");
67 		return PTR_ERR(ts_nbus->strobe);
68 	}
69 
70 	ts_nbus->ale = devm_gpiod_get(&pdev->dev, "ts,ale", GPIOD_OUT_HIGH);
71 	if (IS_ERR(ts_nbus->ale)) {
72 		dev_err(&pdev->dev, "failed to retrieve ts,ale-gpio from dts\n");
73 		return PTR_ERR(ts_nbus->ale);
74 	}
75 
76 	ts_nbus->rdy = devm_gpiod_get(&pdev->dev, "ts,rdy", GPIOD_IN);
77 	if (IS_ERR(ts_nbus->rdy)) {
78 		dev_err(&pdev->dev, "failed to retrieve ts,rdy-gpio from dts\n");
79 		return PTR_ERR(ts_nbus->rdy);
80 	}
81 
82 	return 0;
83 }
84 
85 /*
86  * the data gpios are used for reading and writing values, their directions
87  * should be adjusted accordingly.
88  */
ts_nbus_set_direction(struct ts_nbus * ts_nbus,int direction)89 static void ts_nbus_set_direction(struct ts_nbus *ts_nbus, int direction)
90 {
91 	int i;
92 
93 	for (i = 0; i < 8; i++) {
94 		if (direction == TS_NBUS_DIRECTION_IN)
95 			gpiod_direction_input(ts_nbus->data->desc[i]);
96 		else
97 			/* when used as output the default state of the data
98 			 * lines are set to high */
99 			gpiod_direction_output(ts_nbus->data->desc[i], 1);
100 	}
101 }
102 
103 /*
104  * reset the bus in its initial state.
105  * The data, csn, strobe and ale lines must be zero'ed to let the FPGA knows a
106  * new transaction can be process.
107  */
ts_nbus_reset_bus(struct ts_nbus * ts_nbus)108 static void ts_nbus_reset_bus(struct ts_nbus *ts_nbus)
109 {
110 	DECLARE_BITMAP(values, 8);
111 
112 	values[0] = 0;
113 
114 	gpiod_set_array_value_cansleep(8, ts_nbus->data->desc,
115 				       ts_nbus->data->info, values);
116 	gpiod_set_value_cansleep(ts_nbus->csn, 0);
117 	gpiod_set_value_cansleep(ts_nbus->strobe, 0);
118 	gpiod_set_value_cansleep(ts_nbus->ale, 0);
119 }
120 
121 /*
122  * let the FPGA knows it can process.
123  */
ts_nbus_start_transaction(struct ts_nbus * ts_nbus)124 static void ts_nbus_start_transaction(struct ts_nbus *ts_nbus)
125 {
126 	gpiod_set_value_cansleep(ts_nbus->strobe, 1);
127 }
128 
129 /*
130  * read a byte value from the data gpios.
131  * return 0 on success or negative errno on failure.
132  */
ts_nbus_read_byte(struct ts_nbus * ts_nbus,u8 * val)133 static int ts_nbus_read_byte(struct ts_nbus *ts_nbus, u8 *val)
134 {
135 	struct gpio_descs *gpios = ts_nbus->data;
136 	int ret, i;
137 
138 	*val = 0;
139 	for (i = 0; i < 8; i++) {
140 		ret = gpiod_get_value_cansleep(gpios->desc[i]);
141 		if (ret < 0)
142 			return ret;
143 		if (ret)
144 			*val |= BIT(i);
145 	}
146 
147 	return 0;
148 }
149 
150 /*
151  * set the data gpios accordingly to the byte value.
152  */
ts_nbus_write_byte(struct ts_nbus * ts_nbus,u8 byte)153 static void ts_nbus_write_byte(struct ts_nbus *ts_nbus, u8 byte)
154 {
155 	struct gpio_descs *gpios = ts_nbus->data;
156 	DECLARE_BITMAP(values, 8);
157 
158 	values[0] = byte;
159 
160 	gpiod_set_array_value_cansleep(8, gpios->desc, gpios->info, values);
161 }
162 
163 /*
164  * reading the bus consists of resetting the bus, then notifying the FPGA to
165  * send the data in the data gpios and return the read value.
166  * return 0 on success or negative errno on failure.
167  */
ts_nbus_read_bus(struct ts_nbus * ts_nbus,u8 * val)168 static int ts_nbus_read_bus(struct ts_nbus *ts_nbus, u8 *val)
169 {
170 	ts_nbus_reset_bus(ts_nbus);
171 	ts_nbus_start_transaction(ts_nbus);
172 
173 	return ts_nbus_read_byte(ts_nbus, val);
174 }
175 
176 /*
177  * writing to the bus consists of resetting the bus, then define the type of
178  * command (address/value), write the data and notify the FPGA to retrieve the
179  * value in the data gpios.
180  */
ts_nbus_write_bus(struct ts_nbus * ts_nbus,int cmd,u8 val)181 static void ts_nbus_write_bus(struct ts_nbus *ts_nbus, int cmd, u8 val)
182 {
183 	ts_nbus_reset_bus(ts_nbus);
184 
185 	if (cmd == TS_NBUS_WRITE_ADR)
186 		gpiod_set_value_cansleep(ts_nbus->ale, 1);
187 
188 	ts_nbus_write_byte(ts_nbus, val);
189 	ts_nbus_start_transaction(ts_nbus);
190 }
191 
192 /*
193  * read the value in the FPGA register at the given address.
194  * return 0 on success or negative errno on failure.
195  */
ts_nbus_read(struct ts_nbus * ts_nbus,u8 adr,u16 * val)196 int ts_nbus_read(struct ts_nbus *ts_nbus, u8 adr, u16 *val)
197 {
198 	int ret, i;
199 	u8 byte;
200 
201 	/* bus access must be atomic */
202 	mutex_lock(&ts_nbus->lock);
203 
204 	/* set the bus in read mode */
205 	gpiod_set_value_cansleep(ts_nbus->txrx, 0);
206 
207 	/* write address */
208 	ts_nbus_write_bus(ts_nbus, TS_NBUS_WRITE_ADR, adr);
209 
210 	/* set the data gpios direction as input before reading */
211 	ts_nbus_set_direction(ts_nbus, TS_NBUS_DIRECTION_IN);
212 
213 	/* reading value MSB first */
214 	do {
215 		*val = 0;
216 		byte = 0;
217 		for (i = 1; i >= 0; i--) {
218 			/* read a byte from the bus, leave on error */
219 			ret = ts_nbus_read_bus(ts_nbus, &byte);
220 			if (ret < 0)
221 				goto err;
222 
223 			/* append the byte read to the final value */
224 			*val |= byte << (i * 8);
225 		}
226 		gpiod_set_value_cansleep(ts_nbus->csn, 1);
227 		ret = gpiod_get_value_cansleep(ts_nbus->rdy);
228 	} while (ret);
229 
230 err:
231 	/* restore the data gpios direction as output after reading */
232 	ts_nbus_set_direction(ts_nbus, TS_NBUS_DIRECTION_OUT);
233 
234 	mutex_unlock(&ts_nbus->lock);
235 
236 	return ret;
237 }
238 EXPORT_SYMBOL_GPL(ts_nbus_read);
239 
240 /*
241  * write the desired value in the FPGA register at the given address.
242  */
ts_nbus_write(struct ts_nbus * ts_nbus,u8 adr,u16 val)243 int ts_nbus_write(struct ts_nbus *ts_nbus, u8 adr, u16 val)
244 {
245 	int i;
246 
247 	/* bus access must be atomic */
248 	mutex_lock(&ts_nbus->lock);
249 
250 	/* set the bus in write mode */
251 	gpiod_set_value_cansleep(ts_nbus->txrx, 1);
252 
253 	/* write address */
254 	ts_nbus_write_bus(ts_nbus, TS_NBUS_WRITE_ADR, adr);
255 
256 	/* writing value MSB first */
257 	for (i = 1; i >= 0; i--)
258 		ts_nbus_write_bus(ts_nbus, TS_NBUS_WRITE_VAL, (u8)(val >> (i * 8)));
259 
260 	/* wait for completion */
261 	gpiod_set_value_cansleep(ts_nbus->csn, 1);
262 	while (gpiod_get_value_cansleep(ts_nbus->rdy) != 0) {
263 		gpiod_set_value_cansleep(ts_nbus->csn, 0);
264 		gpiod_set_value_cansleep(ts_nbus->csn, 1);
265 	}
266 
267 	mutex_unlock(&ts_nbus->lock);
268 
269 	return 0;
270 }
271 EXPORT_SYMBOL_GPL(ts_nbus_write);
272 
ts_nbus_probe(struct platform_device * pdev)273 static int ts_nbus_probe(struct platform_device *pdev)
274 {
275 	struct pwm_device *pwm;
276 	struct pwm_args pargs;
277 	struct device *dev = &pdev->dev;
278 	struct ts_nbus *ts_nbus;
279 	int ret;
280 
281 	ts_nbus = devm_kzalloc(dev, sizeof(*ts_nbus), GFP_KERNEL);
282 	if (!ts_nbus)
283 		return -ENOMEM;
284 
285 	mutex_init(&ts_nbus->lock);
286 
287 	ret = ts_nbus_init_pdata(pdev, ts_nbus);
288 	if (ret < 0)
289 		return ret;
290 
291 	pwm = devm_pwm_get(dev, NULL);
292 	if (IS_ERR(pwm)) {
293 		ret = PTR_ERR(pwm);
294 		if (ret != -EPROBE_DEFER)
295 			dev_err(dev, "unable to request PWM\n");
296 		return ret;
297 	}
298 
299 	pwm_get_args(pwm, &pargs);
300 	if (!pargs.period) {
301 		dev_err(&pdev->dev, "invalid PWM period\n");
302 		return -EINVAL;
303 	}
304 
305 	/*
306 	 * FIXME: pwm_apply_args() should be removed when switching to
307 	 * the atomic PWM API.
308 	 */
309 	pwm_apply_args(pwm);
310 	ret = pwm_config(pwm, pargs.period, pargs.period);
311 	if (ret < 0)
312 		return ret;
313 
314 	/*
315 	 * we can now start the FPGA and populate the peripherals.
316 	 */
317 	pwm_enable(pwm);
318 	ts_nbus->pwm = pwm;
319 
320 	/*
321 	 * let the child nodes retrieve this instance of the ts-nbus.
322 	 */
323 	dev_set_drvdata(dev, ts_nbus);
324 
325 	ret = of_platform_populate(dev->of_node, NULL, NULL, dev);
326 	if (ret < 0)
327 		return ret;
328 
329 	dev_info(dev, "initialized\n");
330 
331 	return 0;
332 }
333 
ts_nbus_remove(struct platform_device * pdev)334 static int ts_nbus_remove(struct platform_device *pdev)
335 {
336 	struct ts_nbus *ts_nbus = dev_get_drvdata(&pdev->dev);
337 
338 	/* shutdown the FPGA */
339 	mutex_lock(&ts_nbus->lock);
340 	pwm_disable(ts_nbus->pwm);
341 	mutex_unlock(&ts_nbus->lock);
342 
343 	return 0;
344 }
345 
346 static const struct of_device_id ts_nbus_of_match[] = {
347 	{ .compatible = "technologic,ts-nbus", },
348 	{ },
349 };
350 MODULE_DEVICE_TABLE(of, ts_nbus_of_match);
351 
352 static struct platform_driver ts_nbus_driver = {
353 	.probe		= ts_nbus_probe,
354 	.remove		= ts_nbus_remove,
355 	.driver		= {
356 		.name	= "ts_nbus",
357 		.of_match_table = ts_nbus_of_match,
358 	},
359 };
360 
361 module_platform_driver(ts_nbus_driver);
362 
363 MODULE_ALIAS("platform:ts_nbus");
364 MODULE_AUTHOR("Sebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com>");
365 MODULE_DESCRIPTION("Technologic Systems NBUS");
366 MODULE_LICENSE("GPL v2");
367