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