1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * i2c-smbus.c - SMBus extensions to the I2C protocol
4 *
5 * Copyright (C) 2008 David Brownell
6 * Copyright (C) 2010-2019 Jean Delvare <jdelvare@suse.de>
7 */
8
9#include <linux/device.h>
10#include <linux/dmi.h>
11#include <linux/i2c.h>
12#include <linux/i2c-smbus.h>
13#include <linux/interrupt.h>
14#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/of_irq.h>
17#include <linux/slab.h>
18#include <linux/workqueue.h>
19
20struct i2c_smbus_alert {
21	struct work_struct	alert;
22	struct i2c_client	*ara;		/* Alert response address */
23};
24
25struct alert_data {
26	unsigned short		addr;
27	enum i2c_alert_protocol	type;
28	unsigned int		data;
29};
30
31/* If this is the alerting device, notify its driver */
32static int smbus_do_alert(struct device *dev, void *addrp)
33{
34	struct i2c_client *client = i2c_verify_client(dev);
35	struct alert_data *data = addrp;
36	struct i2c_driver *driver;
37
38	if (!client || client->addr != data->addr)
39		return 0;
40	if (client->flags & I2C_CLIENT_TEN)
41		return 0;
42
43	/*
44	 * Drivers should either disable alerts, or provide at least
45	 * a minimal handler.  Lock so the driver won't change.
46	 */
47	device_lock(dev);
48	if (client->dev.driver) {
49		driver = to_i2c_driver(client->dev.driver);
50		if (driver->alert)
51			driver->alert(client, data->type, data->data);
52		else
53			dev_warn(&client->dev, "no driver alert()!\n");
54	} else
55		dev_dbg(&client->dev, "alert with no driver\n");
56	device_unlock(dev);
57
58	/* Stop iterating after we find the device */
59	return -EBUSY;
60}
61
62/*
63 * The alert IRQ handler needs to hand work off to a task which can issue
64 * SMBus calls, because those sleeping calls can't be made in IRQ context.
65 */
66static irqreturn_t smbus_alert(int irq, void *d)
67{
68	struct i2c_smbus_alert *alert = d;
69	struct i2c_client *ara;
70
71	ara = alert->ara;
72
73	for (;;) {
74		s32 status;
75		struct alert_data data;
76
77		/*
78		 * Devices with pending alerts reply in address order, low
79		 * to high, because of slave transmit arbitration.  After
80		 * responding, an SMBus device stops asserting SMBALERT#.
81		 *
82		 * Note that SMBus 2.0 reserves 10-bit addresses for future
83		 * use.  We neither handle them, nor try to use PEC here.
84		 */
85		status = i2c_smbus_read_byte(ara);
86		if (status < 0)
87			break;
88
89		data.data = status & 1;
90		data.addr = status >> 1;
91		data.type = I2C_PROTOCOL_SMBUS_ALERT;
92
93		dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n",
94			data.addr, data.data);
95
96		/* Notify driver for the device which issued the alert */
97		device_for_each_child(&ara->adapter->dev, &data,
98				      smbus_do_alert);
99	}
100
101	return IRQ_HANDLED;
102}
103
104static void smbalert_work(struct work_struct *work)
105{
106	struct i2c_smbus_alert *alert;
107
108	alert = container_of(work, struct i2c_smbus_alert, alert);
109
110	smbus_alert(0, alert);
111
112}
113
114/* Setup SMBALERT# infrastructure */
115static int smbalert_probe(struct i2c_client *ara,
116			  const struct i2c_device_id *id)
117{
118	struct i2c_smbus_alert_setup *setup = dev_get_platdata(&ara->dev);
119	struct i2c_smbus_alert *alert;
120	struct i2c_adapter *adapter = ara->adapter;
121	int res, irq;
122
123	alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert),
124			     GFP_KERNEL);
125	if (!alert)
126		return -ENOMEM;
127
128	if (setup) {
129		irq = setup->irq;
130	} else {
131		irq = of_irq_get_byname(adapter->dev.of_node, "smbus_alert");
132		if (irq <= 0)
133			return irq;
134	}
135
136	INIT_WORK(&alert->alert, smbalert_work);
137	alert->ara = ara;
138
139	if (irq > 0) {
140		res = devm_request_threaded_irq(&ara->dev, irq,
141						NULL, smbus_alert,
142						IRQF_SHARED | IRQF_ONESHOT,
143						"smbus_alert", alert);
144		if (res)
145			return res;
146	}
147
148	i2c_set_clientdata(ara, alert);
149	dev_info(&adapter->dev, "supports SMBALERT#\n");
150
151	return 0;
152}
153
154/* IRQ and memory resources are managed so they are freed automatically */
155static int smbalert_remove(struct i2c_client *ara)
156{
157	struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
158
159	cancel_work_sync(&alert->alert);
160	return 0;
161}
162
163static const struct i2c_device_id smbalert_ids[] = {
164	{ "smbus_alert", 0 },
165	{ /* LIST END */ }
166};
167MODULE_DEVICE_TABLE(i2c, smbalert_ids);
168
169static struct i2c_driver smbalert_driver = {
170	.driver = {
171		.name	= "smbus_alert",
172	},
173	.probe		= smbalert_probe,
174	.remove		= smbalert_remove,
175	.id_table	= smbalert_ids,
176};
177
178/**
179 * i2c_handle_smbus_alert - Handle an SMBus alert
180 * @ara: the ARA client on the relevant adapter
181 * Context: can't sleep
182 *
183 * Helper function to be called from an I2C bus driver's interrupt
184 * handler. It will schedule the alert work, in turn calling the
185 * corresponding I2C device driver's alert function.
186 *
187 * It is assumed that ara is a valid i2c client previously returned by
188 * i2c_new_smbus_alert_device().
189 */
190int i2c_handle_smbus_alert(struct i2c_client *ara)
191{
192	struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
193
194	return schedule_work(&alert->alert);
195}
196EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
197
198module_i2c_driver(smbalert_driver);
199
200#if IS_ENABLED(CONFIG_I2C_SLAVE)
201#define SMBUS_HOST_NOTIFY_LEN	3
202struct i2c_slave_host_notify_status {
203	u8 index;
204	u8 addr;
205};
206
207static int i2c_slave_host_notify_cb(struct i2c_client *client,
208				    enum i2c_slave_event event, u8 *val)
209{
210	struct i2c_slave_host_notify_status *status = client->dev.platform_data;
211
212	switch (event) {
213	case I2C_SLAVE_WRITE_RECEIVED:
214		/* We only retrieve the first byte received (addr)
215		 * since there is currently no support to retrieve the data
216		 * parameter from the client.
217		 */
218		if (status->index == 0)
219			status->addr = *val;
220		if (status->index < U8_MAX)
221			status->index++;
222		break;
223	case I2C_SLAVE_STOP:
224		if (status->index == SMBUS_HOST_NOTIFY_LEN)
225			i2c_handle_smbus_host_notify(client->adapter,
226						     status->addr);
227		fallthrough;
228	case I2C_SLAVE_WRITE_REQUESTED:
229		status->index = 0;
230		break;
231	case I2C_SLAVE_READ_REQUESTED:
232	case I2C_SLAVE_READ_PROCESSED:
233		*val = 0xff;
234		break;
235	}
236
237	return 0;
238}
239
240/**
241 * i2c_new_slave_host_notify_device - get a client for SMBus host-notify support
242 * @adapter: the target adapter
243 * Context: can sleep
244 *
245 * Setup handling of the SMBus host-notify protocol on a given I2C bus segment.
246 *
247 * Handling is done by creating a device and its callback and handling data
248 * received via the SMBus host-notify address (0x8)
249 *
250 * This returns the client, which should be ultimately freed using
251 * i2c_free_slave_host_notify_device(); or an ERRPTR to indicate an error.
252 */
253struct i2c_client *i2c_new_slave_host_notify_device(struct i2c_adapter *adapter)
254{
255	struct i2c_board_info host_notify_board_info = {
256		I2C_BOARD_INFO("smbus_host_notify", 0x08),
257		.flags  = I2C_CLIENT_SLAVE,
258	};
259	struct i2c_slave_host_notify_status *status;
260	struct i2c_client *client;
261	int ret;
262
263	status = kzalloc(sizeof(struct i2c_slave_host_notify_status),
264			 GFP_KERNEL);
265	if (!status)
266		return ERR_PTR(-ENOMEM);
267
268	host_notify_board_info.platform_data = status;
269
270	client = i2c_new_client_device(adapter, &host_notify_board_info);
271	if (IS_ERR(client)) {
272		kfree(status);
273		return client;
274	}
275
276	ret = i2c_slave_register(client, i2c_slave_host_notify_cb);
277	if (ret) {
278		i2c_unregister_device(client);
279		kfree(status);
280		return ERR_PTR(ret);
281	}
282
283	return client;
284}
285EXPORT_SYMBOL_GPL(i2c_new_slave_host_notify_device);
286
287/**
288 * i2c_free_slave_host_notify_device - free the client for SMBus host-notify
289 * support
290 * @client: the client to free
291 * Context: can sleep
292 *
293 * Free the i2c_client allocated via i2c_new_slave_host_notify_device
294 */
295void i2c_free_slave_host_notify_device(struct i2c_client *client)
296{
297	if (IS_ERR_OR_NULL(client))
298		return;
299
300	i2c_slave_unregister(client);
301	kfree(client->dev.platform_data);
302	i2c_unregister_device(client);
303}
304EXPORT_SYMBOL_GPL(i2c_free_slave_host_notify_device);
305#endif
306
307/*
308 * SPD is not part of SMBus but we include it here for convenience as the
309 * target systems are the same.
310 * Restrictions to automatic SPD instantiation:
311 *  - Only works if all filled slots have the same memory type
312 *  - Only works for DDR2, DDR3 and DDR4 for now
313 *  - Only works on systems with 1 to 4 memory slots
314 */
315#if IS_ENABLED(CONFIG_DMI)
316void i2c_register_spd(struct i2c_adapter *adap)
317{
318	int n, slot_count = 0, dimm_count = 0;
319	u16 handle;
320	u8 common_mem_type = 0x0, mem_type;
321	u64 mem_size;
322	const char *name;
323
324	while ((handle = dmi_memdev_handle(slot_count)) != 0xffff) {
325		slot_count++;
326
327		/* Skip empty slots */
328		mem_size = dmi_memdev_size(handle);
329		if (!mem_size)
330			continue;
331
332		/* Skip undefined memory type */
333		mem_type = dmi_memdev_type(handle);
334		if (mem_type <= 0x02)		/* Invalid, Other, Unknown */
335			continue;
336
337		if (!common_mem_type) {
338			/* First filled slot */
339			common_mem_type = mem_type;
340		} else {
341			/* Check that all filled slots have the same type */
342			if (mem_type != common_mem_type) {
343				dev_warn(&adap->dev,
344					 "Different memory types mixed, not instantiating SPD\n");
345				return;
346			}
347		}
348		dimm_count++;
349	}
350
351	/* No useful DMI data, bail out */
352	if (!dimm_count)
353		return;
354
355	dev_info(&adap->dev, "%d/%d memory slots populated (from DMI)\n",
356		 dimm_count, slot_count);
357
358	if (slot_count > 4) {
359		dev_warn(&adap->dev,
360			 "Systems with more than 4 memory slots not supported yet, not instantiating SPD\n");
361		return;
362	}
363
364	switch (common_mem_type) {
365	case 0x13:	/* DDR2 */
366	case 0x18:	/* DDR3 */
367	case 0x1C:	/* LPDDR2 */
368	case 0x1D:	/* LPDDR3 */
369		name = "spd";
370		break;
371	case 0x1A:	/* DDR4 */
372	case 0x1E:	/* LPDDR4 */
373		name = "ee1004";
374		break;
375	default:
376		dev_info(&adap->dev,
377			 "Memory type 0x%02x not supported yet, not instantiating SPD\n",
378			 common_mem_type);
379		return;
380	}
381
382	/*
383	 * We don't know in which slots the memory modules are. We could
384	 * try to guess from the slot names, but that would be rather complex
385	 * and unreliable, so better probe all possible addresses until we
386	 * have found all memory modules.
387	 */
388	for (n = 0; n < slot_count && dimm_count; n++) {
389		struct i2c_board_info info;
390		unsigned short addr_list[2];
391
392		memset(&info, 0, sizeof(struct i2c_board_info));
393		strlcpy(info.type, name, I2C_NAME_SIZE);
394		addr_list[0] = 0x50 + n;
395		addr_list[1] = I2C_CLIENT_END;
396
397		if (!IS_ERR(i2c_new_scanned_device(adap, &info, addr_list, NULL))) {
398			dev_info(&adap->dev,
399				 "Successfully instantiated SPD at 0x%hx\n",
400				 addr_list[0]);
401			dimm_count--;
402		}
403	}
404}
405EXPORT_SYMBOL_GPL(i2c_register_spd);
406#endif
407
408MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
409MODULE_DESCRIPTION("SMBus protocol extensions support");
410MODULE_LICENSE("GPL");
411