1 /*
2 * NBUS driver for TS-4600 based boards
3 *
4 * Copyright (c) 2016 - Savoir-faire Linux
5 * Author: Sebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com>
6 *
7 * This file is licensed under the terms of the GNU General Public
8 * License version 2. This program is licensed "as is" without any
9 * warranty of any kind, whether express or implied.
10 *
11 * This driver implements a GPIOs bit-banged bus, called the NBUS by Technologic
12 * Systems. It is used to communicate with the peripherals in the FPGA on the
13 * TS-4600 SoM.
14 */
15
16 #include <linux/bitops.h>
17 #include <linux/gpio/consumer.h>
18 #include <linux/kernel.h>
19 #include <linux/module.h>
20 #include <linux/mutex.h>
21 #include <linux/of_platform.h>
22 #include <linux/platform_device.h>
23 #include <linux/pwm.h>
24 #include <linux/ts-nbus.h>
25
26 #define TS_NBUS_DIRECTION_IN 0
27 #define TS_NBUS_DIRECTION_OUT 1
28 #define TS_NBUS_WRITE_ADR 0
29 #define TS_NBUS_WRITE_VAL 1
30
31 struct ts_nbus {
32 struct pwm_device *pwm;
33 struct gpio_descs *data;
34 struct gpio_desc *csn;
35 struct gpio_desc *txrx;
36 struct gpio_desc *strobe;
37 struct gpio_desc *ale;
38 struct gpio_desc *rdy;
39 struct mutex lock;
40 };
41
42 /*
43 * request all gpios required by the bus.
44 */
ts_nbus_init_pdata(struct platform_device * pdev,struct ts_nbus * ts_nbus)45 static int ts_nbus_init_pdata(struct platform_device *pdev, struct ts_nbus
46 *ts_nbus)
47 {
48 ts_nbus->data = devm_gpiod_get_array(&pdev->dev, "ts,data",
49 GPIOD_OUT_HIGH);
50 if (IS_ERR(ts_nbus->data)) {
51 dev_err(&pdev->dev, "failed to retrieve ts,data-gpio from dts\n");
52 return PTR_ERR(ts_nbus->data);
53 }
54
55 ts_nbus->csn = devm_gpiod_get(&pdev->dev, "ts,csn", GPIOD_OUT_HIGH);
56 if (IS_ERR(ts_nbus->csn)) {
57 dev_err(&pdev->dev, "failed to retrieve ts,csn-gpio from dts\n");
58 return PTR_ERR(ts_nbus->csn);
59 }
60
61 ts_nbus->txrx = devm_gpiod_get(&pdev->dev, "ts,txrx", GPIOD_OUT_HIGH);
62 if (IS_ERR(ts_nbus->txrx)) {
63 dev_err(&pdev->dev, "failed to retrieve ts,txrx-gpio from dts\n");
64 return PTR_ERR(ts_nbus->txrx);
65 }
66
67 ts_nbus->strobe = devm_gpiod_get(&pdev->dev, "ts,strobe", GPIOD_OUT_HIGH);
68 if (IS_ERR(ts_nbus->strobe)) {
69 dev_err(&pdev->dev, "failed to retrieve ts,strobe-gpio from dts\n");
70 return PTR_ERR(ts_nbus->strobe);
71 }
72
73 ts_nbus->ale = devm_gpiod_get(&pdev->dev, "ts,ale", GPIOD_OUT_HIGH);
74 if (IS_ERR(ts_nbus->ale)) {
75 dev_err(&pdev->dev, "failed to retrieve ts,ale-gpio from dts\n");
76 return PTR_ERR(ts_nbus->ale);
77 }
78
79 ts_nbus->rdy = devm_gpiod_get(&pdev->dev, "ts,rdy", GPIOD_IN);
80 if (IS_ERR(ts_nbus->rdy)) {
81 dev_err(&pdev->dev, "failed to retrieve ts,rdy-gpio from dts\n");
82 return PTR_ERR(ts_nbus->rdy);
83 }
84
85 return 0;
86 }
87
88 /*
89 * the data gpios are used for reading and writing values, their directions
90 * should be adjusted accordingly.
91 */
ts_nbus_set_direction(struct ts_nbus * ts_nbus,int direction)92 static void ts_nbus_set_direction(struct ts_nbus *ts_nbus, int direction)
93 {
94 int i;
95
96 for (i = 0; i < 8; i++) {
97 if (direction == TS_NBUS_DIRECTION_IN)
98 gpiod_direction_input(ts_nbus->data->desc[i]);
99 else
100 /* when used as output the default state of the data
101 * lines are set to high */
102 gpiod_direction_output(ts_nbus->data->desc[i], 1);
103 }
104 }
105
106 /*
107 * reset the bus in its initial state.
108 * The data, csn, strobe and ale lines must be zero'ed to let the FPGA knows a
109 * new transaction can be process.
110 */
ts_nbus_reset_bus(struct ts_nbus * ts_nbus)111 static void ts_nbus_reset_bus(struct ts_nbus *ts_nbus)
112 {
113 int i;
114 int values[8];
115
116 for (i = 0; i < 8; i++)
117 values[i] = 0;
118
119 gpiod_set_array_value_cansleep(8, ts_nbus->data->desc, values);
120 gpiod_set_value_cansleep(ts_nbus->csn, 0);
121 gpiod_set_value_cansleep(ts_nbus->strobe, 0);
122 gpiod_set_value_cansleep(ts_nbus->ale, 0);
123 }
124
125 /*
126 * let the FPGA knows it can process.
127 */
ts_nbus_start_transaction(struct ts_nbus * ts_nbus)128 static void ts_nbus_start_transaction(struct ts_nbus *ts_nbus)
129 {
130 gpiod_set_value_cansleep(ts_nbus->strobe, 1);
131 }
132
133 /*
134 * read a byte value from the data gpios.
135 * return 0 on success or negative errno on failure.
136 */
ts_nbus_read_byte(struct ts_nbus * ts_nbus,u8 * val)137 static int ts_nbus_read_byte(struct ts_nbus *ts_nbus, u8 *val)
138 {
139 struct gpio_descs *gpios = ts_nbus->data;
140 int ret, i;
141
142 *val = 0;
143 for (i = 0; i < 8; i++) {
144 ret = gpiod_get_value_cansleep(gpios->desc[i]);
145 if (ret < 0)
146 return ret;
147 if (ret)
148 *val |= BIT(i);
149 }
150
151 return 0;
152 }
153
154 /*
155 * set the data gpios accordingly to the byte value.
156 */
ts_nbus_write_byte(struct ts_nbus * ts_nbus,u8 byte)157 static void ts_nbus_write_byte(struct ts_nbus *ts_nbus, u8 byte)
158 {
159 struct gpio_descs *gpios = ts_nbus->data;
160 int i;
161 int values[8];
162
163 for (i = 0; i < 8; i++)
164 if (byte & BIT(i))
165 values[i] = 1;
166 else
167 values[i] = 0;
168
169 gpiod_set_array_value_cansleep(8, gpios->desc, values);
170 }
171
172 /*
173 * reading the bus consists of resetting the bus, then notifying the FPGA to
174 * send the data in the data gpios and return the read value.
175 * return 0 on success or negative errno on failure.
176 */
ts_nbus_read_bus(struct ts_nbus * ts_nbus,u8 * val)177 static int ts_nbus_read_bus(struct ts_nbus *ts_nbus, u8 *val)
178 {
179 ts_nbus_reset_bus(ts_nbus);
180 ts_nbus_start_transaction(ts_nbus);
181
182 return ts_nbus_read_byte(ts_nbus, val);
183 }
184
185 /*
186 * writing to the bus consists of resetting the bus, then define the type of
187 * command (address/value), write the data and notify the FPGA to retrieve the
188 * value in the data gpios.
189 */
ts_nbus_write_bus(struct ts_nbus * ts_nbus,int cmd,u8 val)190 static void ts_nbus_write_bus(struct ts_nbus *ts_nbus, int cmd, u8 val)
191 {
192 ts_nbus_reset_bus(ts_nbus);
193
194 if (cmd == TS_NBUS_WRITE_ADR)
195 gpiod_set_value_cansleep(ts_nbus->ale, 1);
196
197 ts_nbus_write_byte(ts_nbus, val);
198 ts_nbus_start_transaction(ts_nbus);
199 }
200
201 /*
202 * read the value in the FPGA register at the given address.
203 * return 0 on success or negative errno on failure.
204 */
ts_nbus_read(struct ts_nbus * ts_nbus,u8 adr,u16 * val)205 int ts_nbus_read(struct ts_nbus *ts_nbus, u8 adr, u16 *val)
206 {
207 int ret, i;
208 u8 byte;
209
210 /* bus access must be atomic */
211 mutex_lock(&ts_nbus->lock);
212
213 /* set the bus in read mode */
214 gpiod_set_value_cansleep(ts_nbus->txrx, 0);
215
216 /* write address */
217 ts_nbus_write_bus(ts_nbus, TS_NBUS_WRITE_ADR, adr);
218
219 /* set the data gpios direction as input before reading */
220 ts_nbus_set_direction(ts_nbus, TS_NBUS_DIRECTION_IN);
221
222 /* reading value MSB first */
223 do {
224 *val = 0;
225 byte = 0;
226 for (i = 1; i >= 0; i--) {
227 /* read a byte from the bus, leave on error */
228 ret = ts_nbus_read_bus(ts_nbus, &byte);
229 if (ret < 0)
230 goto err;
231
232 /* append the byte read to the final value */
233 *val |= byte << (i * 8);
234 }
235 gpiod_set_value_cansleep(ts_nbus->csn, 1);
236 ret = gpiod_get_value_cansleep(ts_nbus->rdy);
237 } while (ret);
238
239 err:
240 /* restore the data gpios direction as output after reading */
241 ts_nbus_set_direction(ts_nbus, TS_NBUS_DIRECTION_OUT);
242
243 mutex_unlock(&ts_nbus->lock);
244
245 return ret;
246 }
247 EXPORT_SYMBOL_GPL(ts_nbus_read);
248
249 /*
250 * write the desired value in the FPGA register at the given address.
251 */
ts_nbus_write(struct ts_nbus * ts_nbus,u8 adr,u16 val)252 int ts_nbus_write(struct ts_nbus *ts_nbus, u8 adr, u16 val)
253 {
254 int i;
255
256 /* bus access must be atomic */
257 mutex_lock(&ts_nbus->lock);
258
259 /* set the bus in write mode */
260 gpiod_set_value_cansleep(ts_nbus->txrx, 1);
261
262 /* write address */
263 ts_nbus_write_bus(ts_nbus, TS_NBUS_WRITE_ADR, adr);
264
265 /* writing value MSB first */
266 for (i = 1; i >= 0; i--)
267 ts_nbus_write_bus(ts_nbus, TS_NBUS_WRITE_VAL, (u8)(val >> (i * 8)));
268
269 /* wait for completion */
270 gpiod_set_value_cansleep(ts_nbus->csn, 1);
271 while (gpiod_get_value_cansleep(ts_nbus->rdy) != 0) {
272 gpiod_set_value_cansleep(ts_nbus->csn, 0);
273 gpiod_set_value_cansleep(ts_nbus->csn, 1);
274 }
275
276 mutex_unlock(&ts_nbus->lock);
277
278 return 0;
279 }
280 EXPORT_SYMBOL_GPL(ts_nbus_write);
281
ts_nbus_probe(struct platform_device * pdev)282 static int ts_nbus_probe(struct platform_device *pdev)
283 {
284 struct pwm_device *pwm;
285 struct pwm_args pargs;
286 struct device *dev = &pdev->dev;
287 struct ts_nbus *ts_nbus;
288 int ret;
289
290 ts_nbus = devm_kzalloc(dev, sizeof(*ts_nbus), GFP_KERNEL);
291 if (!ts_nbus)
292 return -ENOMEM;
293
294 mutex_init(&ts_nbus->lock);
295
296 ret = ts_nbus_init_pdata(pdev, ts_nbus);
297 if (ret < 0)
298 return ret;
299
300 pwm = devm_pwm_get(dev, NULL);
301 if (IS_ERR(pwm)) {
302 ret = PTR_ERR(pwm);
303 if (ret != -EPROBE_DEFER)
304 dev_err(dev, "unable to request PWM\n");
305 return ret;
306 }
307
308 pwm_get_args(pwm, &pargs);
309 if (!pargs.period) {
310 dev_err(&pdev->dev, "invalid PWM period\n");
311 return -EINVAL;
312 }
313
314 /*
315 * FIXME: pwm_apply_args() should be removed when switching to
316 * the atomic PWM API.
317 */
318 pwm_apply_args(pwm);
319 ret = pwm_config(pwm, pargs.period, pargs.period);
320 if (ret < 0)
321 return ret;
322
323 /*
324 * we can now start the FPGA and populate the peripherals.
325 */
326 pwm_enable(pwm);
327 ts_nbus->pwm = pwm;
328
329 /*
330 * let the child nodes retrieve this instance of the ts-nbus.
331 */
332 dev_set_drvdata(dev, ts_nbus);
333
334 ret = of_platform_populate(dev->of_node, NULL, NULL, dev);
335 if (ret < 0)
336 return ret;
337
338 dev_info(dev, "initialized\n");
339
340 return 0;
341 }
342
ts_nbus_remove(struct platform_device * pdev)343 static int ts_nbus_remove(struct platform_device *pdev)
344 {
345 struct ts_nbus *ts_nbus = dev_get_drvdata(&pdev->dev);
346
347 /* shutdown the FPGA */
348 mutex_lock(&ts_nbus->lock);
349 pwm_disable(ts_nbus->pwm);
350 mutex_unlock(&ts_nbus->lock);
351
352 return 0;
353 }
354
355 static const struct of_device_id ts_nbus_of_match[] = {
356 { .compatible = "technologic,ts-nbus", },
357 { },
358 };
359 MODULE_DEVICE_TABLE(of, ts_nbus_of_match);
360
361 static struct platform_driver ts_nbus_driver = {
362 .probe = ts_nbus_probe,
363 .remove = ts_nbus_remove,
364 .driver = {
365 .name = "ts_nbus",
366 .of_match_table = ts_nbus_of_match,
367 },
368 };
369
370 module_platform_driver(ts_nbus_driver);
371
372 MODULE_ALIAS("platform:ts_nbus");
373 MODULE_AUTHOR("Sebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com>");
374 MODULE_DESCRIPTION("Technologic Systems NBUS");
375 MODULE_LICENSE("GPL v2");
376