1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * Bitbanging I2C bus driver using the GPIO API |
4 | * |
5 | * Copyright (C) 2007 Atmel Corporation |
6 | */ |
7 | #include <linux/completion.h> |
8 | #include <linux/debugfs.h> |
9 | #include <linux/delay.h> |
10 | #include <linux/gpio/consumer.h> |
11 | #include <linux/i2c-algo-bit.h> |
12 | #include <linux/i2c.h> |
13 | #include <linux/init.h> |
14 | #include <linux/interrupt.h> |
15 | #include <linux/module.h> |
16 | #include <linux/platform_data/i2c-gpio.h> |
17 | #include <linux/platform_device.h> |
18 | #include <linux/property.h> |
19 | #include <linux/slab.h> |
20 | |
21 | struct i2c_gpio_private_data { |
22 | struct gpio_desc *sda; |
23 | struct gpio_desc *scl; |
24 | struct i2c_adapter adap; |
25 | struct i2c_algo_bit_data bit_data; |
26 | struct i2c_gpio_platform_data pdata; |
27 | #ifdef CONFIG_I2C_GPIO_FAULT_INJECTOR |
28 | struct dentry *debug_dir; |
29 | /* these must be protected by bus lock */ |
30 | struct completion scl_irq_completion; |
31 | u64 scl_irq_data; |
32 | #endif |
33 | }; |
34 | |
35 | /* |
36 | * Toggle SDA by changing the output value of the pin. This is only |
37 | * valid for pins configured as open drain (i.e. setting the value |
38 | * high effectively turns off the output driver.) |
39 | */ |
40 | static void i2c_gpio_setsda_val(void *data, int state) |
41 | { |
42 | struct i2c_gpio_private_data *priv = data; |
43 | |
44 | gpiod_set_value_cansleep(desc: priv->sda, value: state); |
45 | } |
46 | |
47 | /* |
48 | * Toggle SCL by changing the output value of the pin. This is used |
49 | * for pins that are configured as open drain and for output-only |
50 | * pins. The latter case will break the i2c protocol, but it will |
51 | * often work in practice. |
52 | */ |
53 | static void i2c_gpio_setscl_val(void *data, int state) |
54 | { |
55 | struct i2c_gpio_private_data *priv = data; |
56 | |
57 | gpiod_set_value_cansleep(desc: priv->scl, value: state); |
58 | } |
59 | |
60 | static int i2c_gpio_getsda(void *data) |
61 | { |
62 | struct i2c_gpio_private_data *priv = data; |
63 | |
64 | return gpiod_get_value_cansleep(desc: priv->sda); |
65 | } |
66 | |
67 | static int i2c_gpio_getscl(void *data) |
68 | { |
69 | struct i2c_gpio_private_data *priv = data; |
70 | |
71 | return gpiod_get_value_cansleep(desc: priv->scl); |
72 | } |
73 | |
74 | #ifdef CONFIG_I2C_GPIO_FAULT_INJECTOR |
75 | static struct dentry *i2c_gpio_debug_dir; |
76 | |
77 | #define setsda(bd, val) ((bd)->setsda((bd)->data, val)) |
78 | #define setscl(bd, val) ((bd)->setscl((bd)->data, val)) |
79 | #define getsda(bd) ((bd)->getsda((bd)->data)) |
80 | #define getscl(bd) ((bd)->getscl((bd)->data)) |
81 | |
82 | #define WIRE_ATTRIBUTE(wire) \ |
83 | static int fops_##wire##_get(void *data, u64 *val) \ |
84 | { \ |
85 | struct i2c_gpio_private_data *priv = data; \ |
86 | \ |
87 | i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER); \ |
88 | *val = get##wire(&priv->bit_data); \ |
89 | i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER); \ |
90 | return 0; \ |
91 | } \ |
92 | static int fops_##wire##_set(void *data, u64 val) \ |
93 | { \ |
94 | struct i2c_gpio_private_data *priv = data; \ |
95 | \ |
96 | i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER); \ |
97 | set##wire(&priv->bit_data, val); \ |
98 | i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER); \ |
99 | return 0; \ |
100 | } \ |
101 | DEFINE_DEBUGFS_ATTRIBUTE(fops_##wire, fops_##wire##_get, fops_##wire##_set, "%llu\n") |
102 | |
103 | WIRE_ATTRIBUTE(scl); |
104 | WIRE_ATTRIBUTE(sda); |
105 | |
106 | static void i2c_gpio_incomplete_transfer(struct i2c_gpio_private_data *priv, |
107 | u32 pattern, u8 pattern_size) |
108 | { |
109 | struct i2c_algo_bit_data *bit_data = &priv->bit_data; |
110 | int i; |
111 | |
112 | i2c_lock_bus(adapter: &priv->adap, I2C_LOCK_ROOT_ADAPTER); |
113 | |
114 | /* START condition */ |
115 | setsda(bit_data, 0); |
116 | udelay(bit_data->udelay); |
117 | |
118 | /* Send pattern, request ACK, don't send STOP */ |
119 | for (i = pattern_size - 1; i >= 0; i--) { |
120 | setscl(bit_data, 0); |
121 | udelay(bit_data->udelay / 2); |
122 | setsda(bit_data, (pattern >> i) & 1); |
123 | udelay((bit_data->udelay + 1) / 2); |
124 | setscl(bit_data, 1); |
125 | udelay(bit_data->udelay); |
126 | } |
127 | |
128 | i2c_unlock_bus(adapter: &priv->adap, I2C_LOCK_ROOT_ADAPTER); |
129 | } |
130 | |
131 | static int fops_incomplete_addr_phase_set(void *data, u64 addr) |
132 | { |
133 | struct i2c_gpio_private_data *priv = data; |
134 | u32 pattern; |
135 | |
136 | if (addr > 0x7f) |
137 | return -EINVAL; |
138 | |
139 | /* ADDR (7 bit) + RD (1 bit) + Client ACK, keep SDA hi (1 bit) */ |
140 | pattern = (addr << 2) | 3; |
141 | |
142 | i2c_gpio_incomplete_transfer(priv, pattern, pattern_size: 9); |
143 | |
144 | return 0; |
145 | } |
146 | DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_addr_phase, NULL, fops_incomplete_addr_phase_set, "%llu\n" ); |
147 | |
148 | static int fops_incomplete_write_byte_set(void *data, u64 addr) |
149 | { |
150 | struct i2c_gpio_private_data *priv = data; |
151 | u32 pattern; |
152 | |
153 | if (addr > 0x7f) |
154 | return -EINVAL; |
155 | |
156 | /* ADDR (7 bit) + WR (1 bit) + Client ACK (1 bit) */ |
157 | pattern = (addr << 2) | 1; |
158 | /* 0x00 (8 bit) + Client ACK, keep SDA hi (1 bit) */ |
159 | pattern = (pattern << 9) | 1; |
160 | |
161 | i2c_gpio_incomplete_transfer(priv, pattern, pattern_size: 18); |
162 | |
163 | return 0; |
164 | } |
165 | DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_write_byte, NULL, fops_incomplete_write_byte_set, "%llu\n" ); |
166 | |
167 | static int i2c_gpio_fi_act_on_scl_irq(struct i2c_gpio_private_data *priv, |
168 | irqreturn_t handler(int, void*)) |
169 | { |
170 | int ret, irq = gpiod_to_irq(desc: priv->scl); |
171 | |
172 | if (irq < 0) |
173 | return irq; |
174 | |
175 | i2c_lock_bus(adapter: &priv->adap, I2C_LOCK_ROOT_ADAPTER); |
176 | |
177 | ret = gpiod_direction_input(desc: priv->scl); |
178 | if (ret) |
179 | goto unlock; |
180 | |
181 | reinit_completion(x: &priv->scl_irq_completion); |
182 | |
183 | ret = request_irq(irq, handler, IRQF_TRIGGER_FALLING, |
184 | name: "i2c_gpio_fault_injector_scl_irq" , dev: priv); |
185 | if (ret) |
186 | goto output; |
187 | |
188 | wait_for_completion_interruptible(x: &priv->scl_irq_completion); |
189 | |
190 | free_irq(irq, priv); |
191 | output: |
192 | ret = gpiod_direction_output(desc: priv->scl, value: 1) ?: ret; |
193 | unlock: |
194 | i2c_unlock_bus(adapter: &priv->adap, I2C_LOCK_ROOT_ADAPTER); |
195 | |
196 | return ret; |
197 | } |
198 | |
199 | static irqreturn_t lose_arbitration_irq(int irq, void *dev_id) |
200 | { |
201 | struct i2c_gpio_private_data *priv = dev_id; |
202 | |
203 | setsda(&priv->bit_data, 0); |
204 | udelay(priv->scl_irq_data); |
205 | setsda(&priv->bit_data, 1); |
206 | |
207 | complete(&priv->scl_irq_completion); |
208 | |
209 | return IRQ_HANDLED; |
210 | } |
211 | |
212 | static int fops_lose_arbitration_set(void *data, u64 duration) |
213 | { |
214 | struct i2c_gpio_private_data *priv = data; |
215 | |
216 | if (duration > 100 * 1000) |
217 | return -EINVAL; |
218 | |
219 | priv->scl_irq_data = duration; |
220 | /* |
221 | * Interrupt on falling SCL. This ensures that the master under test has |
222 | * really started the transfer. Interrupt on falling SDA did only |
223 | * exercise 'bus busy' detection on some HW but not 'arbitration lost'. |
224 | * Note that the interrupt latency may cause the first bits to be |
225 | * transmitted correctly. |
226 | */ |
227 | return i2c_gpio_fi_act_on_scl_irq(priv, handler: lose_arbitration_irq); |
228 | } |
229 | DEFINE_DEBUGFS_ATTRIBUTE(fops_lose_arbitration, NULL, fops_lose_arbitration_set, "%llu\n" ); |
230 | |
231 | static irqreturn_t inject_panic_irq(int irq, void *dev_id) |
232 | { |
233 | struct i2c_gpio_private_data *priv = dev_id; |
234 | |
235 | udelay(priv->scl_irq_data); |
236 | panic(fmt: "I2C fault injector induced panic" ); |
237 | |
238 | return IRQ_HANDLED; |
239 | } |
240 | |
241 | static int fops_inject_panic_set(void *data, u64 duration) |
242 | { |
243 | struct i2c_gpio_private_data *priv = data; |
244 | |
245 | if (duration > 100 * 1000) |
246 | return -EINVAL; |
247 | |
248 | priv->scl_irq_data = duration; |
249 | /* |
250 | * Interrupt on falling SCL. This ensures that the master under test has |
251 | * really started the transfer. |
252 | */ |
253 | return i2c_gpio_fi_act_on_scl_irq(priv, handler: inject_panic_irq); |
254 | } |
255 | DEFINE_DEBUGFS_ATTRIBUTE(fops_inject_panic, NULL, fops_inject_panic_set, "%llu\n" ); |
256 | |
257 | static void i2c_gpio_fault_injector_init(struct platform_device *pdev) |
258 | { |
259 | struct i2c_gpio_private_data *priv = platform_get_drvdata(pdev); |
260 | |
261 | /* |
262 | * If there will be a debugfs-dir per i2c adapter somewhen, put the |
263 | * 'fault-injector' dir there. Until then, we have a global dir with |
264 | * all adapters as subdirs. |
265 | */ |
266 | if (!i2c_gpio_debug_dir) |
267 | i2c_gpio_debug_dir = debugfs_create_dir(name: "i2c-fault-injector" , NULL); |
268 | |
269 | priv->debug_dir = debugfs_create_dir(name: pdev->name, parent: i2c_gpio_debug_dir); |
270 | |
271 | init_completion(x: &priv->scl_irq_completion); |
272 | |
273 | debugfs_create_file_unsafe(name: "incomplete_address_phase" , mode: 0200, parent: priv->debug_dir, |
274 | data: priv, fops: &fops_incomplete_addr_phase); |
275 | debugfs_create_file_unsafe(name: "incomplete_write_byte" , mode: 0200, parent: priv->debug_dir, |
276 | data: priv, fops: &fops_incomplete_write_byte); |
277 | if (priv->bit_data.getscl) { |
278 | debugfs_create_file_unsafe(name: "inject_panic" , mode: 0200, parent: priv->debug_dir, |
279 | data: priv, fops: &fops_inject_panic); |
280 | debugfs_create_file_unsafe(name: "lose_arbitration" , mode: 0200, parent: priv->debug_dir, |
281 | data: priv, fops: &fops_lose_arbitration); |
282 | } |
283 | debugfs_create_file_unsafe(name: "scl" , mode: 0600, parent: priv->debug_dir, data: priv, fops: &fops_scl); |
284 | debugfs_create_file_unsafe(name: "sda" , mode: 0600, parent: priv->debug_dir, data: priv, fops: &fops_sda); |
285 | } |
286 | |
287 | static void i2c_gpio_fault_injector_exit(struct platform_device *pdev) |
288 | { |
289 | struct i2c_gpio_private_data *priv = platform_get_drvdata(pdev); |
290 | |
291 | debugfs_remove_recursive(dentry: priv->debug_dir); |
292 | } |
293 | #else |
294 | static inline void i2c_gpio_fault_injector_init(struct platform_device *pdev) {} |
295 | static inline void i2c_gpio_fault_injector_exit(struct platform_device *pdev) {} |
296 | #endif /* CONFIG_I2C_GPIO_FAULT_INJECTOR*/ |
297 | |
298 | /* Get i2c-gpio properties from DT or ACPI table */ |
299 | static void i2c_gpio_get_properties(struct device *dev, |
300 | struct i2c_gpio_platform_data *pdata) |
301 | { |
302 | u32 reg; |
303 | |
304 | device_property_read_u32(dev, propname: "i2c-gpio,delay-us" , val: &pdata->udelay); |
305 | |
306 | if (!device_property_read_u32(dev, propname: "i2c-gpio,timeout-ms" , val: ®)) |
307 | pdata->timeout = msecs_to_jiffies(m: reg); |
308 | |
309 | pdata->sda_is_open_drain = |
310 | device_property_read_bool(dev, propname: "i2c-gpio,sda-open-drain" ); |
311 | pdata->scl_is_open_drain = |
312 | device_property_read_bool(dev, propname: "i2c-gpio,scl-open-drain" ); |
313 | pdata->scl_is_output_only = |
314 | device_property_read_bool(dev, propname: "i2c-gpio,scl-output-only" ); |
315 | pdata->sda_is_output_only = |
316 | device_property_read_bool(dev, propname: "i2c-gpio,sda-output-only" ); |
317 | pdata->sda_has_no_pullup = |
318 | device_property_read_bool(dev, propname: "i2c-gpio,sda-has-no-pullup" ); |
319 | pdata->scl_has_no_pullup = |
320 | device_property_read_bool(dev, propname: "i2c-gpio,scl-has-no-pullup" ); |
321 | } |
322 | |
323 | static struct gpio_desc *i2c_gpio_get_desc(struct device *dev, |
324 | const char *con_id, |
325 | unsigned int index, |
326 | enum gpiod_flags gflags) |
327 | { |
328 | struct gpio_desc *retdesc; |
329 | int ret; |
330 | |
331 | retdesc = devm_gpiod_get(dev, con_id, flags: gflags); |
332 | if (!IS_ERR(ptr: retdesc)) { |
333 | dev_dbg(dev, "got GPIO from name %s\n" , con_id); |
334 | return retdesc; |
335 | } |
336 | |
337 | retdesc = devm_gpiod_get_index(dev, NULL, idx: index, flags: gflags); |
338 | if (!IS_ERR(ptr: retdesc)) { |
339 | dev_dbg(dev, "got GPIO from index %u\n" , index); |
340 | return retdesc; |
341 | } |
342 | |
343 | ret = PTR_ERR(ptr: retdesc); |
344 | |
345 | /* FIXME: hack in the old code, is this really necessary? */ |
346 | if (ret == -EINVAL) |
347 | retdesc = ERR_PTR(error: -EPROBE_DEFER); |
348 | |
349 | /* This happens if the GPIO driver is not yet probed, let's defer */ |
350 | if (ret == -ENOENT) |
351 | retdesc = ERR_PTR(error: -EPROBE_DEFER); |
352 | |
353 | if (PTR_ERR(ptr: retdesc) != -EPROBE_DEFER) |
354 | dev_err(dev, "error trying to get descriptor: %d\n" , ret); |
355 | |
356 | return retdesc; |
357 | } |
358 | |
359 | static int i2c_gpio_probe(struct platform_device *pdev) |
360 | { |
361 | struct i2c_gpio_private_data *priv; |
362 | struct i2c_gpio_platform_data *pdata; |
363 | struct i2c_algo_bit_data *bit_data; |
364 | struct i2c_adapter *adap; |
365 | struct device *dev = &pdev->dev; |
366 | struct fwnode_handle *fwnode = dev_fwnode(dev); |
367 | enum gpiod_flags gflags; |
368 | int ret; |
369 | |
370 | priv = devm_kzalloc(dev, size: sizeof(*priv), GFP_KERNEL); |
371 | if (!priv) |
372 | return -ENOMEM; |
373 | |
374 | adap = &priv->adap; |
375 | bit_data = &priv->bit_data; |
376 | pdata = &priv->pdata; |
377 | |
378 | if (fwnode) { |
379 | i2c_gpio_get_properties(dev, pdata); |
380 | } else { |
381 | /* |
382 | * If all platform data settings are zero it is OK |
383 | * to not provide any platform data from the board. |
384 | */ |
385 | if (dev_get_platdata(dev)) |
386 | memcpy(pdata, dev_get_platdata(dev), sizeof(*pdata)); |
387 | } |
388 | |
389 | /* |
390 | * First get the GPIO pins; if it fails, we'll defer the probe. |
391 | * If the SCL/SDA lines are marked "open drain" by platform data or |
392 | * device tree then this means that something outside of our control is |
393 | * marking these lines to be handled as open drain, and we should just |
394 | * handle them as we handle any other output. Else we enforce open |
395 | * drain as this is required for an I2C bus. |
396 | */ |
397 | if (pdata->sda_is_open_drain || pdata->sda_has_no_pullup) |
398 | gflags = GPIOD_OUT_HIGH; |
399 | else |
400 | gflags = GPIOD_OUT_HIGH_OPEN_DRAIN; |
401 | priv->sda = i2c_gpio_get_desc(dev, con_id: "sda" , index: 0, gflags); |
402 | if (IS_ERR(ptr: priv->sda)) |
403 | return PTR_ERR(ptr: priv->sda); |
404 | |
405 | if (pdata->scl_is_open_drain || pdata->scl_has_no_pullup) |
406 | gflags = GPIOD_OUT_HIGH; |
407 | else |
408 | gflags = GPIOD_OUT_HIGH_OPEN_DRAIN; |
409 | priv->scl = i2c_gpio_get_desc(dev, con_id: "scl" , index: 1, gflags); |
410 | if (IS_ERR(ptr: priv->scl)) |
411 | return PTR_ERR(ptr: priv->scl); |
412 | |
413 | if (gpiod_cansleep(desc: priv->sda) || gpiod_cansleep(desc: priv->scl)) |
414 | dev_warn(dev, "Slow GPIO pins might wreak havoc into I2C/SMBus bus timing" ); |
415 | else |
416 | bit_data->can_do_atomic = true; |
417 | |
418 | bit_data->setsda = i2c_gpio_setsda_val; |
419 | bit_data->setscl = i2c_gpio_setscl_val; |
420 | |
421 | if (!pdata->scl_is_output_only) |
422 | bit_data->getscl = i2c_gpio_getscl; |
423 | if (!pdata->sda_is_output_only) |
424 | bit_data->getsda = i2c_gpio_getsda; |
425 | |
426 | if (pdata->udelay) |
427 | bit_data->udelay = pdata->udelay; |
428 | else if (pdata->scl_is_output_only) |
429 | bit_data->udelay = 50; /* 10 kHz */ |
430 | else |
431 | bit_data->udelay = 5; /* 100 kHz */ |
432 | |
433 | if (pdata->timeout) |
434 | bit_data->timeout = pdata->timeout; |
435 | else |
436 | bit_data->timeout = HZ / 10; /* 100 ms */ |
437 | |
438 | bit_data->data = priv; |
439 | |
440 | adap->owner = THIS_MODULE; |
441 | if (fwnode) |
442 | strscpy(p: adap->name, q: dev_name(dev), size: sizeof(adap->name)); |
443 | else |
444 | snprintf(buf: adap->name, size: sizeof(adap->name), fmt: "i2c-gpio%d" , pdev->id); |
445 | |
446 | adap->algo_data = bit_data; |
447 | adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD; |
448 | adap->dev.parent = dev; |
449 | device_set_node(dev: &adap->dev, fwnode); |
450 | |
451 | adap->nr = pdev->id; |
452 | ret = i2c_bit_add_numbered_bus(adap); |
453 | if (ret) |
454 | return ret; |
455 | |
456 | platform_set_drvdata(pdev, data: priv); |
457 | |
458 | /* |
459 | * FIXME: using global GPIO numbers is not helpful. If/when we |
460 | * get accessors to get the actual name of the GPIO line, |
461 | * from the descriptor, then provide that instead. |
462 | */ |
463 | dev_info(dev, "using lines %u (SDA) and %u (SCL%s)\n" , |
464 | desc_to_gpio(priv->sda), desc_to_gpio(priv->scl), |
465 | pdata->scl_is_output_only |
466 | ? ", no clock stretching" : "" ); |
467 | |
468 | i2c_gpio_fault_injector_init(pdev); |
469 | |
470 | return 0; |
471 | } |
472 | |
473 | static void i2c_gpio_remove(struct platform_device *pdev) |
474 | { |
475 | struct i2c_gpio_private_data *priv; |
476 | struct i2c_adapter *adap; |
477 | |
478 | i2c_gpio_fault_injector_exit(pdev); |
479 | |
480 | priv = platform_get_drvdata(pdev); |
481 | adap = &priv->adap; |
482 | |
483 | i2c_del_adapter(adap); |
484 | } |
485 | |
486 | static const struct of_device_id i2c_gpio_dt_ids[] = { |
487 | { .compatible = "i2c-gpio" , }, |
488 | { /* sentinel */ } |
489 | }; |
490 | |
491 | MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids); |
492 | |
493 | static const struct acpi_device_id i2c_gpio_acpi_match[] = { |
494 | { "LOON0005" }, /* LoongArch */ |
495 | { } |
496 | }; |
497 | MODULE_DEVICE_TABLE(acpi, i2c_gpio_acpi_match); |
498 | |
499 | static struct platform_driver i2c_gpio_driver = { |
500 | .driver = { |
501 | .name = "i2c-gpio" , |
502 | .of_match_table = i2c_gpio_dt_ids, |
503 | .acpi_match_table = i2c_gpio_acpi_match, |
504 | }, |
505 | .probe = i2c_gpio_probe, |
506 | .remove_new = i2c_gpio_remove, |
507 | }; |
508 | |
509 | static int __init i2c_gpio_init(void) |
510 | { |
511 | int ret; |
512 | |
513 | ret = platform_driver_register(&i2c_gpio_driver); |
514 | if (ret) |
515 | printk(KERN_ERR "i2c-gpio: probe failed: %d\n" , ret); |
516 | |
517 | return ret; |
518 | } |
519 | subsys_initcall(i2c_gpio_init); |
520 | |
521 | static void __exit i2c_gpio_exit(void) |
522 | { |
523 | platform_driver_unregister(&i2c_gpio_driver); |
524 | } |
525 | module_exit(i2c_gpio_exit); |
526 | |
527 | MODULE_AUTHOR("Haavard Skinnemoen (Atmel)" ); |
528 | MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver" ); |
529 | MODULE_LICENSE("GPL v2" ); |
530 | MODULE_ALIAS("platform:i2c-gpio" ); |
531 | |