Commit | Line | Data |
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9ee0a055 DK |
1 | /* |
2 | * GPIO based serio bus driver for bit banging the PS/2 protocol | |
3 | * | |
4 | * Author: Danilo Krummrich <danilokrummrich@dk-develop.de> | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or modify | |
7 | * it under the terms of the GNU General Public License version 2 as | |
8 | * published by the Free Software Foundation. | |
9 | */ | |
10 | ||
11 | #include <linux/gpio/consumer.h> | |
12 | #include <linux/interrupt.h> | |
13 | #include <linux/module.h> | |
14 | #include <linux/serio.h> | |
15 | #include <linux/slab.h> | |
16 | #include <linux/platform_device.h> | |
17 | #include <linux/workqueue.h> | |
18 | #include <linux/completion.h> | |
19 | #include <linux/mutex.h> | |
20 | #include <linux/preempt.h> | |
21 | #include <linux/property.h> | |
22 | #include <linux/of.h> | |
23 | #include <linux/jiffies.h> | |
24 | #include <linux/delay.h> | |
25 | ||
26 | #define DRIVER_NAME "ps2-gpio" | |
27 | ||
28 | #define PS2_MODE_RX 0 | |
29 | #define PS2_MODE_TX 1 | |
30 | ||
31 | #define PS2_START_BIT 0 | |
32 | #define PS2_DATA_BIT0 1 | |
33 | #define PS2_DATA_BIT1 2 | |
34 | #define PS2_DATA_BIT2 3 | |
35 | #define PS2_DATA_BIT3 4 | |
36 | #define PS2_DATA_BIT4 5 | |
37 | #define PS2_DATA_BIT5 6 | |
38 | #define PS2_DATA_BIT6 7 | |
39 | #define PS2_DATA_BIT7 8 | |
40 | #define PS2_PARITY_BIT 9 | |
41 | #define PS2_STOP_BIT 10 | |
42 | #define PS2_TX_TIMEOUT 11 | |
43 | #define PS2_ACK_BIT 12 | |
44 | ||
45 | #define PS2_DEV_RET_ACK 0xfa | |
46 | #define PS2_DEV_RET_NACK 0xfe | |
47 | ||
48 | #define PS2_CMD_RESEND 0xfe | |
49 | ||
50 | struct ps2_gpio_data { | |
51 | struct device *dev; | |
52 | struct serio *serio; | |
53 | unsigned char mode; | |
54 | struct gpio_desc *gpio_clk; | |
55 | struct gpio_desc *gpio_data; | |
56 | bool write_enable; | |
57 | int irq; | |
58 | unsigned char rx_cnt; | |
59 | unsigned char rx_byte; | |
60 | unsigned char tx_cnt; | |
61 | unsigned char tx_byte; | |
62 | struct completion tx_done; | |
63 | struct mutex tx_mutex; | |
64 | struct delayed_work tx_work; | |
65 | }; | |
66 | ||
67 | static int ps2_gpio_open(struct serio *serio) | |
68 | { | |
69 | struct ps2_gpio_data *drvdata = serio->port_data; | |
70 | ||
71 | enable_irq(drvdata->irq); | |
72 | return 0; | |
73 | } | |
74 | ||
75 | static void ps2_gpio_close(struct serio *serio) | |
76 | { | |
77 | struct ps2_gpio_data *drvdata = serio->port_data; | |
78 | ||
79 | disable_irq(drvdata->irq); | |
80 | } | |
81 | ||
82 | static int __ps2_gpio_write(struct serio *serio, unsigned char val) | |
83 | { | |
84 | struct ps2_gpio_data *drvdata = serio->port_data; | |
85 | ||
86 | disable_irq_nosync(drvdata->irq); | |
87 | gpiod_direction_output(drvdata->gpio_clk, 0); | |
88 | ||
89 | drvdata->mode = PS2_MODE_TX; | |
90 | drvdata->tx_byte = val; | |
91 | ||
92 | schedule_delayed_work(&drvdata->tx_work, usecs_to_jiffies(200)); | |
93 | ||
94 | return 0; | |
95 | } | |
96 | ||
97 | static int ps2_gpio_write(struct serio *serio, unsigned char val) | |
98 | { | |
99 | struct ps2_gpio_data *drvdata = serio->port_data; | |
100 | int ret = 0; | |
101 | ||
102 | if (in_task()) { | |
103 | mutex_lock(&drvdata->tx_mutex); | |
104 | __ps2_gpio_write(serio, val); | |
105 | if (!wait_for_completion_timeout(&drvdata->tx_done, | |
106 | msecs_to_jiffies(10000))) | |
107 | ret = SERIO_TIMEOUT; | |
108 | mutex_unlock(&drvdata->tx_mutex); | |
109 | } else { | |
110 | __ps2_gpio_write(serio, val); | |
111 | } | |
112 | ||
113 | return ret; | |
114 | } | |
115 | ||
116 | static void ps2_gpio_tx_work_fn(struct work_struct *work) | |
117 | { | |
118 | struct delayed_work *dwork = to_delayed_work(work); | |
119 | struct ps2_gpio_data *drvdata = container_of(dwork, | |
120 | struct ps2_gpio_data, | |
121 | tx_work); | |
122 | ||
123 | enable_irq(drvdata->irq); | |
124 | gpiod_direction_output(drvdata->gpio_data, 0); | |
125 | gpiod_direction_input(drvdata->gpio_clk); | |
126 | } | |
127 | ||
128 | static irqreturn_t ps2_gpio_irq_rx(struct ps2_gpio_data *drvdata) | |
129 | { | |
130 | unsigned char byte, cnt; | |
131 | int data; | |
132 | int rxflags = 0; | |
133 | static unsigned long old_jiffies; | |
134 | ||
135 | byte = drvdata->rx_byte; | |
136 | cnt = drvdata->rx_cnt; | |
137 | ||
138 | if (old_jiffies == 0) | |
139 | old_jiffies = jiffies; | |
140 | ||
141 | if ((jiffies - old_jiffies) > usecs_to_jiffies(100)) { | |
142 | dev_err(drvdata->dev, | |
143 | "RX: timeout, probably we missed an interrupt\n"); | |
144 | goto err; | |
145 | } | |
146 | old_jiffies = jiffies; | |
147 | ||
148 | data = gpiod_get_value(drvdata->gpio_data); | |
149 | if (unlikely(data < 0)) { | |
150 | dev_err(drvdata->dev, "RX: failed to get data gpio val: %d\n", | |
151 | data); | |
152 | goto err; | |
153 | } | |
154 | ||
155 | switch (cnt) { | |
156 | case PS2_START_BIT: | |
157 | /* start bit should be low */ | |
158 | if (unlikely(data)) { | |
159 | dev_err(drvdata->dev, "RX: start bit should be low\n"); | |
160 | goto err; | |
161 | } | |
162 | break; | |
163 | case PS2_DATA_BIT0: | |
164 | case PS2_DATA_BIT1: | |
165 | case PS2_DATA_BIT2: | |
166 | case PS2_DATA_BIT3: | |
167 | case PS2_DATA_BIT4: | |
168 | case PS2_DATA_BIT5: | |
169 | case PS2_DATA_BIT6: | |
170 | case PS2_DATA_BIT7: | |
171 | /* processing data bits */ | |
172 | if (data) | |
173 | byte |= (data << (cnt - 1)); | |
174 | break; | |
175 | case PS2_PARITY_BIT: | |
176 | /* check odd parity */ | |
177 | if (!((hweight8(byte) & 1) ^ data)) { | |
178 | rxflags |= SERIO_PARITY; | |
179 | dev_warn(drvdata->dev, "RX: parity error\n"); | |
180 | if (!drvdata->write_enable) | |
181 | goto err; | |
182 | } | |
183 | ||
184 | /* Do not send spurious ACK's and NACK's when write fn is | |
185 | * not provided. | |
186 | */ | |
187 | if (!drvdata->write_enable) { | |
188 | if (byte == PS2_DEV_RET_NACK) | |
189 | goto err; | |
190 | else if (byte == PS2_DEV_RET_ACK) | |
191 | break; | |
192 | } | |
193 | ||
194 | /* Let's send the data without waiting for the stop bit to be | |
195 | * sent. It may happen that we miss the stop bit. When this | |
196 | * happens we have no way to recover from this, certainly | |
197 | * missing the parity bit would be recognized when processing | |
198 | * the stop bit. When missing both, data is lost. | |
199 | */ | |
200 | serio_interrupt(drvdata->serio, byte, rxflags); | |
201 | dev_dbg(drvdata->dev, "RX: sending byte 0x%x\n", byte); | |
202 | break; | |
203 | case PS2_STOP_BIT: | |
204 | /* stop bit should be high */ | |
205 | if (unlikely(!data)) { | |
206 | dev_err(drvdata->dev, "RX: stop bit should be high\n"); | |
207 | goto err; | |
208 | } | |
209 | cnt = byte = 0; | |
210 | old_jiffies = 0; | |
211 | goto end; /* success */ | |
212 | default: | |
213 | dev_err(drvdata->dev, "RX: got out of sync with the device\n"); | |
214 | goto err; | |
215 | } | |
216 | ||
217 | cnt++; | |
218 | goto end; /* success */ | |
219 | ||
220 | err: | |
221 | cnt = byte = 0; | |
222 | old_jiffies = 0; | |
223 | __ps2_gpio_write(drvdata->serio, PS2_CMD_RESEND); | |
224 | end: | |
225 | drvdata->rx_cnt = cnt; | |
226 | drvdata->rx_byte = byte; | |
227 | return IRQ_HANDLED; | |
228 | } | |
229 | ||
230 | static irqreturn_t ps2_gpio_irq_tx(struct ps2_gpio_data *drvdata) | |
231 | { | |
232 | unsigned char byte, cnt; | |
233 | int data; | |
234 | static unsigned long old_jiffies; | |
235 | ||
236 | cnt = drvdata->tx_cnt; | |
237 | byte = drvdata->tx_byte; | |
238 | ||
239 | if (old_jiffies == 0) | |
240 | old_jiffies = jiffies; | |
241 | ||
242 | if ((jiffies - old_jiffies) > usecs_to_jiffies(100)) { | |
243 | dev_err(drvdata->dev, | |
244 | "TX: timeout, probably we missed an interrupt\n"); | |
245 | goto err; | |
246 | } | |
247 | old_jiffies = jiffies; | |
248 | ||
249 | switch (cnt) { | |
250 | case PS2_START_BIT: | |
251 | /* should never happen */ | |
252 | dev_err(drvdata->dev, | |
253 | "TX: start bit should have been sent already\n"); | |
254 | goto err; | |
255 | case PS2_DATA_BIT0: | |
256 | case PS2_DATA_BIT1: | |
257 | case PS2_DATA_BIT2: | |
258 | case PS2_DATA_BIT3: | |
259 | case PS2_DATA_BIT4: | |
260 | case PS2_DATA_BIT5: | |
261 | case PS2_DATA_BIT6: | |
262 | case PS2_DATA_BIT7: | |
263 | data = byte & BIT(cnt - 1); | |
264 | gpiod_set_value(drvdata->gpio_data, data); | |
265 | break; | |
266 | case PS2_PARITY_BIT: | |
267 | /* do odd parity */ | |
268 | data = !(hweight8(byte) & 1); | |
269 | gpiod_set_value(drvdata->gpio_data, data); | |
270 | break; | |
271 | case PS2_STOP_BIT: | |
272 | /* release data line to generate stop bit */ | |
273 | gpiod_direction_input(drvdata->gpio_data); | |
274 | break; | |
275 | case PS2_TX_TIMEOUT: | |
276 | /* Devices generate one extra clock pulse before sending the | |
277 | * acknowledgment. | |
278 | */ | |
279 | break; | |
280 | case PS2_ACK_BIT: | |
281 | gpiod_direction_input(drvdata->gpio_data); | |
282 | data = gpiod_get_value(drvdata->gpio_data); | |
283 | if (data) { | |
284 | dev_warn(drvdata->dev, "TX: received NACK, retry\n"); | |
285 | goto err; | |
286 | } | |
287 | ||
288 | drvdata->mode = PS2_MODE_RX; | |
289 | complete(&drvdata->tx_done); | |
290 | ||
291 | cnt = 1; | |
292 | old_jiffies = 0; | |
293 | goto end; /* success */ | |
294 | default: | |
295 | /* Probably we missed the stop bit. Therefore we release data | |
296 | * line and try again. | |
297 | */ | |
298 | gpiod_direction_input(drvdata->gpio_data); | |
299 | dev_err(drvdata->dev, "TX: got out of sync with the device\n"); | |
300 | goto err; | |
301 | } | |
302 | ||
303 | cnt++; | |
304 | goto end; /* success */ | |
305 | ||
306 | err: | |
307 | cnt = 1; | |
308 | old_jiffies = 0; | |
309 | gpiod_direction_input(drvdata->gpio_data); | |
310 | __ps2_gpio_write(drvdata->serio, drvdata->tx_byte); | |
311 | end: | |
312 | drvdata->tx_cnt = cnt; | |
313 | return IRQ_HANDLED; | |
314 | } | |
315 | ||
316 | static irqreturn_t ps2_gpio_irq(int irq, void *dev_id) | |
317 | { | |
318 | struct ps2_gpio_data *drvdata = dev_id; | |
319 | ||
320 | return drvdata->mode ? ps2_gpio_irq_tx(drvdata) : | |
321 | ps2_gpio_irq_rx(drvdata); | |
322 | } | |
323 | ||
324 | static int ps2_gpio_get_props(struct device *dev, | |
325 | struct ps2_gpio_data *drvdata) | |
326 | { | |
327 | drvdata->gpio_data = devm_gpiod_get(dev, "data", GPIOD_IN); | |
328 | if (IS_ERR(drvdata->gpio_data)) { | |
329 | dev_err(dev, "failed to request data gpio: %ld", | |
330 | PTR_ERR(drvdata->gpio_data)); | |
331 | return PTR_ERR(drvdata->gpio_data); | |
332 | } | |
333 | ||
334 | drvdata->gpio_clk = devm_gpiod_get(dev, "clk", GPIOD_IN); | |
335 | if (IS_ERR(drvdata->gpio_clk)) { | |
336 | dev_err(dev, "failed to request clock gpio: %ld", | |
337 | PTR_ERR(drvdata->gpio_clk)); | |
338 | return PTR_ERR(drvdata->gpio_clk); | |
339 | } | |
340 | ||
341 | drvdata->write_enable = device_property_read_bool(dev, | |
342 | "write-enable"); | |
343 | ||
344 | return 0; | |
345 | } | |
346 | ||
347 | static int ps2_gpio_probe(struct platform_device *pdev) | |
348 | { | |
349 | struct ps2_gpio_data *drvdata; | |
350 | struct serio *serio; | |
351 | struct device *dev = &pdev->dev; | |
352 | int error; | |
353 | ||
354 | drvdata = devm_kzalloc(dev, sizeof(struct ps2_gpio_data), GFP_KERNEL); | |
355 | serio = kzalloc(sizeof(struct serio), GFP_KERNEL); | |
356 | if (!drvdata || !serio) { | |
357 | error = -ENOMEM; | |
358 | goto err_free_serio; | |
359 | } | |
360 | ||
361 | error = ps2_gpio_get_props(dev, drvdata); | |
362 | if (error) | |
363 | goto err_free_serio; | |
364 | ||
365 | if (gpiod_cansleep(drvdata->gpio_data) || | |
366 | gpiod_cansleep(drvdata->gpio_clk)) { | |
367 | dev_err(dev, "GPIO data or clk are connected via slow bus\n"); | |
368 | error = -EINVAL; | |
6a3eafe4 | 369 | goto err_free_serio; |
9ee0a055 DK |
370 | } |
371 | ||
372 | drvdata->irq = platform_get_irq(pdev, 0); | |
373 | if (drvdata->irq < 0) { | |
374 | dev_err(dev, "failed to get irq from platform resource: %d\n", | |
375 | drvdata->irq); | |
376 | error = drvdata->irq; | |
377 | goto err_free_serio; | |
378 | } | |
379 | ||
380 | error = devm_request_irq(dev, drvdata->irq, ps2_gpio_irq, | |
381 | IRQF_NO_THREAD, DRIVER_NAME, drvdata); | |
382 | if (error) { | |
383 | dev_err(dev, "failed to request irq %d: %d\n", | |
384 | drvdata->irq, error); | |
385 | goto err_free_serio; | |
386 | } | |
387 | ||
388 | /* Keep irq disabled until serio->open is called. */ | |
389 | disable_irq(drvdata->irq); | |
390 | ||
391 | serio->id.type = SERIO_8042; | |
392 | serio->open = ps2_gpio_open; | |
393 | serio->close = ps2_gpio_close; | |
394 | /* Write can be enabled in platform/dt data, but possibly it will not | |
395 | * work because of the tough timings. | |
396 | */ | |
397 | serio->write = drvdata->write_enable ? ps2_gpio_write : NULL; | |
398 | serio->port_data = drvdata; | |
399 | serio->dev.parent = dev; | |
400 | strlcpy(serio->name, dev_name(dev), sizeof(serio->name)); | |
401 | strlcpy(serio->phys, dev_name(dev), sizeof(serio->phys)); | |
402 | ||
403 | drvdata->serio = serio; | |
404 | drvdata->dev = dev; | |
405 | drvdata->mode = PS2_MODE_RX; | |
406 | ||
407 | /* Tx count always starts at 1, as the start bit is sent implicitly by | |
408 | * host-to-device communication initialization. | |
409 | */ | |
410 | drvdata->tx_cnt = 1; | |
411 | ||
412 | INIT_DELAYED_WORK(&drvdata->tx_work, ps2_gpio_tx_work_fn); | |
413 | init_completion(&drvdata->tx_done); | |
414 | mutex_init(&drvdata->tx_mutex); | |
415 | ||
416 | serio_register_port(serio); | |
417 | platform_set_drvdata(pdev, drvdata); | |
418 | ||
419 | return 0; /* success */ | |
420 | ||
421 | err_free_serio: | |
422 | kfree(serio); | |
423 | return error; | |
424 | } | |
425 | ||
426 | static int ps2_gpio_remove(struct platform_device *pdev) | |
427 | { | |
428 | struct ps2_gpio_data *drvdata = platform_get_drvdata(pdev); | |
429 | ||
430 | serio_unregister_port(drvdata->serio); | |
431 | return 0; | |
432 | } | |
433 | ||
434 | #if defined(CONFIG_OF) | |
435 | static const struct of_device_id ps2_gpio_match[] = { | |
436 | { .compatible = "ps2-gpio", }, | |
437 | { }, | |
438 | }; | |
439 | MODULE_DEVICE_TABLE(of, ps2_gpio_match); | |
440 | #endif | |
441 | ||
442 | static struct platform_driver ps2_gpio_driver = { | |
443 | .probe = ps2_gpio_probe, | |
444 | .remove = ps2_gpio_remove, | |
445 | .driver = { | |
446 | .name = DRIVER_NAME, | |
447 | .of_match_table = of_match_ptr(ps2_gpio_match), | |
448 | }, | |
449 | }; | |
450 | module_platform_driver(ps2_gpio_driver); | |
451 | ||
452 | MODULE_AUTHOR("Danilo Krummrich <danilokrummrich@dk-develop.de>"); | |
453 | MODULE_DESCRIPTION("GPIO PS2 driver"); | |
454 | MODULE_LICENSE("GPL v2"); |