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
21struct 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 */
39static 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 */
52static 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
59static 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
66static 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) \
81static 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} \
90static 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} \
99DEFINE_DEBUGFS_ATTRIBUTE(fops_##wire, fops_##wire##_get, fops_##wire##_set, "%llu\n")
100
101WIRE_ATTRIBUTE(scl);
102WIRE_ATTRIBUTE(sda);
103
104static 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(usec: 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(usec: bit_data->udelay / 2);
120 setsda(bit_data, (pattern >> i) & 1);
121 udelay(usec: (bit_data->udelay + 1) / 2);
122 setscl(bit_data, 1);
123 udelay(usec: bit_data->udelay);
124 }
125
126 i2c_unlock_bus(adapter: &priv->adap, I2C_LOCK_ROOT_ADAPTER);
127}
128
129static 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}
144DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_addr_phase, NULL, fops_incomplete_addr_phase_set, "%llu\n");
145
146static 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}
163DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_write_byte, NULL, fops_incomplete_write_byte_set, "%llu\n");
164
165static 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
197static 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(usec: priv->scl_irq_data);
203 setsda(&priv->bit_data, 1);
204
205 complete(&priv->scl_irq_completion);
206
207 return IRQ_HANDLED;
208}
209
210static 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 controller under test
220 * has 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}
227DEFINE_DEBUGFS_ATTRIBUTE(fops_lose_arbitration, NULL, fops_lose_arbitration_set, "%llu\n");
228
229static irqreturn_t inject_panic_irq(int irq, void *dev_id)
230{
231 struct i2c_gpio_private_data *priv = dev_id;
232
233 udelay(usec: priv->scl_irq_data);
234 panic(fmt: "I2C fault injector induced panic");
235
236 return IRQ_HANDLED;
237}
238
239static 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 controller under test
249 * has really started the transfer.
250 */
251 return i2c_gpio_fi_act_on_scl_irq(priv, handler: inject_panic_irq);
252}
253DEFINE_DEBUGFS_ATTRIBUTE(fops_inject_panic, NULL, fops_inject_panic_set, "%llu\n");
254
255static 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
275static 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 */
279static 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: &reg))
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
303static 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
339static 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
453static 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
464static const struct of_device_id i2c_gpio_dt_ids[] = {
465 { .compatible = "i2c-gpio", },
466 { /* sentinel */ }
467};
468
469MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids);
470
471static const struct acpi_device_id i2c_gpio_acpi_match[] = {
472 { "LOON0005" }, /* LoongArch */
473 { }
474};
475MODULE_DEVICE_TABLE(acpi, i2c_gpio_acpi_match);
476
477static 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 = i2c_gpio_remove,
485};
486
487static 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}
497subsys_initcall(i2c_gpio_init);
498
499static void __exit i2c_gpio_exit(void)
500{
501 platform_driver_unregister(&i2c_gpio_driver);
502}
503module_exit(i2c_gpio_exit);
504
505MODULE_AUTHOR("Haavard Skinnemoen (Atmel)");
506MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
507MODULE_LICENSE("GPL v2");
508MODULE_ALIAS("platform:i2c-gpio");
509

source code of linux/drivers/i2c/busses/i2c-gpio.c