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	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 */
40static void i2c_gpio_setsda_val(void *data, int state)
41{
42	struct i2c_gpio_private_data *priv = data;
43
44	gpiod_set_value_cansleep(priv->sda, 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 */
53static void i2c_gpio_setscl_val(void *data, int state)
54{
55	struct i2c_gpio_private_data *priv = data;
56
57	gpiod_set_value_cansleep(priv->scl, state);
58}
59
60static int i2c_gpio_getsda(void *data)
61{
62	struct i2c_gpio_private_data *priv = data;
63
64	return gpiod_get_value_cansleep(priv->sda);
65}
66
67static int i2c_gpio_getscl(void *data)
68{
69	struct i2c_gpio_private_data *priv = data;
70
71	return gpiod_get_value_cansleep(priv->scl);
72}
73
74#ifdef CONFIG_I2C_GPIO_FAULT_INJECTOR
75static 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) \
83static 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}								\
92static 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}								\
101DEFINE_DEBUGFS_ATTRIBUTE(fops_##wire, fops_##wire##_get, fops_##wire##_set, "%llu\n")
102
103WIRE_ATTRIBUTE(scl);
104WIRE_ATTRIBUTE(sda);
105
106static 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(&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(&priv->adap, I2C_LOCK_ROOT_ADAPTER);
129}
130
131static 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, 9);
143
144	return 0;
145}
146DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_addr_phase, NULL, fops_incomplete_addr_phase_set, "%llu\n");
147
148static 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, 18);
162
163	return 0;
164}
165DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_write_byte, NULL, fops_incomplete_write_byte_set, "%llu\n");
166
167static 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(priv->scl);
171
172	if (irq < 0)
173		return irq;
174
175	i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);
176
177	ret = gpiod_direction_input(priv->scl);
178	if (ret)
179		goto unlock;
180
181	reinit_completion(&priv->scl_irq_completion);
182
183	ret = request_irq(irq, handler, IRQF_TRIGGER_FALLING,
184			  "i2c_gpio_fault_injector_scl_irq", priv);
185	if (ret)
186		goto output;
187
188	wait_for_completion_interruptible(&priv->scl_irq_completion);
189
190	free_irq(irq, priv);
191 output:
192	ret = gpiod_direction_output(priv->scl, 1) ?: ret;
193 unlock:
194	i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER);
195
196	return ret;
197}
198
199static 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
212static 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, lose_arbitration_irq);
228}
229DEFINE_DEBUGFS_ATTRIBUTE(fops_lose_arbitration, NULL, fops_lose_arbitration_set, "%llu\n");
230
231static 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("I2C fault injector induced panic");
237
238	return IRQ_HANDLED;
239}
240
241static 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, inject_panic_irq);
254}
255DEFINE_DEBUGFS_ATTRIBUTE(fops_inject_panic, NULL, fops_inject_panic_set, "%llu\n");
256
257static 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("i2c-fault-injector", NULL);
268		if (!i2c_gpio_debug_dir)
269			return;
270	}
271
272	priv->debug_dir = debugfs_create_dir(pdev->name, i2c_gpio_debug_dir);
273	if (!priv->debug_dir)
274		return;
275
276	init_completion(&priv->scl_irq_completion);
277
278	debugfs_create_file_unsafe("incomplete_address_phase", 0200, priv->debug_dir,
279				   priv, &fops_incomplete_addr_phase);
280	debugfs_create_file_unsafe("incomplete_write_byte", 0200, priv->debug_dir,
281				   priv, &fops_incomplete_write_byte);
282	if (priv->bit_data.getscl) {
283		debugfs_create_file_unsafe("inject_panic", 0200, priv->debug_dir,
284					   priv, &fops_inject_panic);
285		debugfs_create_file_unsafe("lose_arbitration", 0200, priv->debug_dir,
286					   priv, &fops_lose_arbitration);
287	}
288	debugfs_create_file_unsafe("scl", 0600, priv->debug_dir, priv, &fops_scl);
289	debugfs_create_file_unsafe("sda", 0600, priv->debug_dir, priv, &fops_sda);
290}
291
292static void i2c_gpio_fault_injector_exit(struct platform_device *pdev)
293{
294	struct i2c_gpio_private_data *priv = platform_get_drvdata(pdev);
295
296	debugfs_remove_recursive(priv->debug_dir);
297}
298#else
299static inline void i2c_gpio_fault_injector_init(struct platform_device *pdev) {}
300static inline void i2c_gpio_fault_injector_exit(struct platform_device *pdev) {}
301#endif /* CONFIG_I2C_GPIO_FAULT_INJECTOR*/
302
303/* Get i2c-gpio properties from DT or ACPI table */
304static void i2c_gpio_get_properties(struct device *dev,
305				    struct i2c_gpio_platform_data *pdata)
306{
307	u32 reg;
308
309	device_property_read_u32(dev, "i2c-gpio,delay-us", &pdata->udelay);
310
311	if (!device_property_read_u32(dev, "i2c-gpio,timeout-ms", &reg))
312		pdata->timeout = msecs_to_jiffies(reg);
313
314	pdata->sda_is_open_drain =
315		device_property_read_bool(dev, "i2c-gpio,sda-open-drain");
316	pdata->scl_is_open_drain =
317		device_property_read_bool(dev, "i2c-gpio,scl-open-drain");
318	pdata->scl_is_output_only =
319		device_property_read_bool(dev, "i2c-gpio,scl-output-only");
320	pdata->sda_is_output_only =
321		device_property_read_bool(dev, "i2c-gpio,sda-output-only");
322	pdata->sda_has_no_pullup =
323		device_property_read_bool(dev, "i2c-gpio,sda-has-no-pullup");
324	pdata->scl_has_no_pullup =
325		device_property_read_bool(dev, "i2c-gpio,scl-has-no-pullup");
326}
327
328static struct gpio_desc *i2c_gpio_get_desc(struct device *dev,
329					   const char *con_id,
330					   unsigned int index,
331					   enum gpiod_flags gflags)
332{
333	struct gpio_desc *retdesc;
334	int ret;
335
336	retdesc = devm_gpiod_get(dev, con_id, gflags);
337	if (!IS_ERR(retdesc)) {
338		dev_dbg(dev, "got GPIO from name %s\n", con_id);
339		return retdesc;
340	}
341
342	retdesc = devm_gpiod_get_index(dev, NULL, index, gflags);
343	if (!IS_ERR(retdesc)) {
344		dev_dbg(dev, "got GPIO from index %u\n", index);
345		return retdesc;
346	}
347
348	ret = PTR_ERR(retdesc);
349
350	/* FIXME: hack in the old code, is this really necessary? */
351	if (ret == -EINVAL)
352		retdesc = ERR_PTR(-EPROBE_DEFER);
353
354	/* This happens if the GPIO driver is not yet probed, let's defer */
355	if (ret == -ENOENT)
356		retdesc = ERR_PTR(-EPROBE_DEFER);
357
358	if (PTR_ERR(retdesc) != -EPROBE_DEFER)
359		dev_err(dev, "error trying to get descriptor: %d\n", ret);
360
361	return retdesc;
362}
363
364static int i2c_gpio_probe(struct platform_device *pdev)
365{
366	struct i2c_gpio_private_data *priv;
367	struct i2c_gpio_platform_data *pdata;
368	struct i2c_algo_bit_data *bit_data;
369	struct i2c_adapter *adap;
370	struct device *dev = &pdev->dev;
371	struct fwnode_handle *fwnode = dev_fwnode(dev);
372	enum gpiod_flags gflags;
373	int ret;
374
375	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
376	if (!priv)
377		return -ENOMEM;
378
379	adap = &priv->adap;
380	bit_data = &priv->bit_data;
381	pdata = &priv->pdata;
382
383	if (fwnode) {
384		i2c_gpio_get_properties(dev, pdata);
385	} else {
386		/*
387		 * If all platform data settings are zero it is OK
388		 * to not provide any platform data from the board.
389		 */
390		if (dev_get_platdata(dev))
391			memcpy(pdata, dev_get_platdata(dev), sizeof(*pdata));
392	}
393
394	/*
395	 * First get the GPIO pins; if it fails, we'll defer the probe.
396	 * If the SCL/SDA lines are marked "open drain" by platform data or
397	 * device tree then this means that something outside of our control is
398	 * marking these lines to be handled as open drain, and we should just
399	 * handle them as we handle any other output. Else we enforce open
400	 * drain as this is required for an I2C bus.
401	 */
402	if (pdata->sda_is_open_drain || pdata->sda_has_no_pullup)
403		gflags = GPIOD_OUT_HIGH;
404	else
405		gflags = GPIOD_OUT_HIGH_OPEN_DRAIN;
406	priv->sda = i2c_gpio_get_desc(dev, "sda", 0, gflags);
407	if (IS_ERR(priv->sda))
408		return PTR_ERR(priv->sda);
409
410	if (pdata->scl_is_open_drain || pdata->scl_has_no_pullup)
411		gflags = GPIOD_OUT_HIGH;
412	else
413		gflags = GPIOD_OUT_HIGH_OPEN_DRAIN;
414	priv->scl = i2c_gpio_get_desc(dev, "scl", 1, gflags);
415	if (IS_ERR(priv->scl))
416		return PTR_ERR(priv->scl);
417
418	if (gpiod_cansleep(priv->sda) || gpiod_cansleep(priv->scl))
419		dev_warn(dev, "Slow GPIO pins might wreak havoc into I2C/SMBus bus timing");
420	else
421		bit_data->can_do_atomic = true;
422
423	bit_data->setsda = i2c_gpio_setsda_val;
424	bit_data->setscl = i2c_gpio_setscl_val;
425
426	if (!pdata->scl_is_output_only)
427		bit_data->getscl = i2c_gpio_getscl;
428	if (!pdata->sda_is_output_only)
429		bit_data->getsda = i2c_gpio_getsda;
430
431	if (pdata->udelay)
432		bit_data->udelay = pdata->udelay;
433	else if (pdata->scl_is_output_only)
434		bit_data->udelay = 50;			/* 10 kHz */
435	else
436		bit_data->udelay = 5;			/* 100 kHz */
437
438	if (pdata->timeout)
439		bit_data->timeout = pdata->timeout;
440	else
441		bit_data->timeout = HZ / 10;		/* 100 ms */
442
443	bit_data->data = priv;
444
445	adap->owner = THIS_MODULE;
446	if (fwnode)
447		strscpy(adap->name, dev_name(dev), sizeof(adap->name));
448	else
449		snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
450
451	adap->algo_data = bit_data;
452	adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
453	adap->dev.parent = dev;
454	device_set_node(&adap->dev, fwnode);
455
456	adap->nr = pdev->id;
457	ret = i2c_bit_add_numbered_bus(adap);
458	if (ret)
459		return ret;
460
461	platform_set_drvdata(pdev, priv);
462
463	/*
464	 * FIXME: using global GPIO numbers is not helpful. If/when we
465	 * get accessors to get the actual name of the GPIO line,
466	 * from the descriptor, then provide that instead.
467	 */
468	dev_info(dev, "using lines %u (SDA) and %u (SCL%s)\n",
469		 desc_to_gpio(priv->sda), desc_to_gpio(priv->scl),
470		 pdata->scl_is_output_only
471		 ? ", no clock stretching" : "");
472
473	i2c_gpio_fault_injector_init(pdev);
474
475	return 0;
476}
477
478static void i2c_gpio_remove(struct platform_device *pdev)
479{
480	struct i2c_gpio_private_data *priv;
481	struct i2c_adapter *adap;
482
483	i2c_gpio_fault_injector_exit(pdev);
484
485	priv = platform_get_drvdata(pdev);
486	adap = &priv->adap;
487
488	i2c_del_adapter(adap);
489}
490
491static const struct of_device_id i2c_gpio_dt_ids[] = {
492	{ .compatible = "i2c-gpio", },
493	{ /* sentinel */ }
494};
495
496MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids);
497
498static const struct acpi_device_id i2c_gpio_acpi_match[] = {
499	{ "LOON0005" }, /* LoongArch */
500	{ }
501};
502MODULE_DEVICE_TABLE(acpi, i2c_gpio_acpi_match);
503
504static struct platform_driver i2c_gpio_driver = {
505	.driver		= {
506		.name	= "i2c-gpio",
507		.of_match_table	= i2c_gpio_dt_ids,
508		.acpi_match_table = i2c_gpio_acpi_match,
509	},
510	.probe		= i2c_gpio_probe,
511	.remove_new	= i2c_gpio_remove,
512};
513
514static int __init i2c_gpio_init(void)
515{
516	int ret;
517
518	ret = platform_driver_register(&i2c_gpio_driver);
519	if (ret)
520		printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
521
522	return ret;
523}
524subsys_initcall(i2c_gpio_init);
525
526static void __exit i2c_gpio_exit(void)
527{
528	platform_driver_unregister(&i2c_gpio_driver);
529}
530module_exit(i2c_gpio_exit);
531
532MODULE_AUTHOR("Haavard Skinnemoen (Atmel)");
533MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
534MODULE_LICENSE("GPL v2");
535MODULE_ALIAS("platform:i2c-gpio");
536