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