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/gpio/consumer.h>
12#include <linux/i2c.h>
13#include <linux/i2c-smbus.h>
14#include <linux/interrupt.h>
15#include <linux/kernel.h>
16#include <linux/module.h>
17#include <linux/property.h>
18#include <linux/slab.h>
19#include <linux/workqueue.h>
20
21struct i2c_smbus_alert {
22 struct work_struct alert;
23 struct i2c_client *ara; /* Alert response address */
24};
25
26struct alert_data {
27 unsigned short addr;
28 enum i2c_alert_protocol type;
29 unsigned int data;
30};
31
32/* If this is the alerting device, notify its driver */
33static int smbus_do_alert(struct device *dev, void *addrp)
34{
35 struct i2c_client *client = i2c_verify_client(dev);
36 struct alert_data *data = addrp;
37 struct i2c_driver *driver;
38 int ret;
39
40 if (!client || client->addr != data->addr)
41 return 0;
42 if (client->flags & I2C_CLIENT_TEN)
43 return 0;
44
45 /*
46 * Drivers should either disable alerts, or provide at least
47 * a minimal handler. Lock so the driver won't change.
48 */
49 device_lock(dev);
50 if (client->dev.driver) {
51 driver = to_i2c_driver(client->dev.driver);
52 if (driver->alert) {
53 /* Stop iterating after we find the device */
54 driver->alert(client, data->type, data->data);
55 ret = -EBUSY;
56 } else {
57 dev_warn(&client->dev, "no driver alert()!\n");
58 ret = -EOPNOTSUPP;
59 }
60 } else {
61 dev_dbg(&client->dev, "alert with no driver\n");
62 ret = -ENODEV;
63 }
64 device_unlock(dev);
65
66 return ret;
67}
68
69/* Same as above, but call back all drivers with alert handler */
70
71static int smbus_do_alert_force(struct device *dev, void *addrp)
72{
73 struct i2c_client *client = i2c_verify_client(dev);
74 struct alert_data *data = addrp;
75 struct i2c_driver *driver;
76
77 if (!client || (client->flags & I2C_CLIENT_TEN))
78 return 0;
79
80 /*
81 * Drivers should either disable alerts, or provide at least
82 * a minimal handler. Lock so the driver won't change.
83 */
84 device_lock(dev);
85 if (client->dev.driver) {
86 driver = to_i2c_driver(client->dev.driver);
87 if (driver->alert)
88 driver->alert(client, data->type, data->data);
89 }
90 device_unlock(dev);
91
92 return 0;
93}
94
95/*
96 * The alert IRQ handler needs to hand work off to a task which can issue
97 * SMBus calls, because those sleeping calls can't be made in IRQ context.
98 */
99static irqreturn_t smbus_alert(int irq, void *d)
100{
101 struct i2c_smbus_alert *alert = d;
102 struct i2c_client *ara;
103 unsigned short prev_addr = I2C_CLIENT_END; /* Not a valid address */
104
105 ara = alert->ara;
106
107 for (;;) {
108 s32 status;
109 struct alert_data data;
110
111 /*
112 * Devices with pending alerts reply in address order, low
113 * to high, because of slave transmit arbitration. After
114 * responding, an SMBus device stops asserting SMBALERT#.
115 *
116 * Note that SMBus 2.0 reserves 10-bit addresses for future
117 * use. We neither handle them, nor try to use PEC here.
118 */
119 status = i2c_smbus_read_byte(client: ara);
120 if (status < 0)
121 break;
122
123 data.data = status & 1;
124 data.addr = status >> 1;
125 data.type = I2C_PROTOCOL_SMBUS_ALERT;
126
127 dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n",
128 data.addr, data.data);
129
130 /* Notify driver for the device which issued the alert */
131 status = device_for_each_child(parent: &ara->adapter->dev, data: &data,
132 fn: smbus_do_alert);
133 /*
134 * If we read the same address more than once, and the alert
135 * was not handled by a driver, it won't do any good to repeat
136 * the loop because it will never terminate. Try again, this
137 * time calling the alert handlers of all devices connected to
138 * the bus, and abort the loop afterwards. If this helps, we
139 * are all set. If it doesn't, there is nothing else we can do,
140 * so we might as well abort the loop.
141 * Note: This assumes that a driver with alert handler handles
142 * the alert properly and clears it if necessary.
143 */
144 if (data.addr == prev_addr && status != -EBUSY) {
145 device_for_each_child(parent: &ara->adapter->dev, data: &data,
146 fn: smbus_do_alert_force);
147 break;
148 }
149 prev_addr = data.addr;
150 }
151
152 return IRQ_HANDLED;
153}
154
155static void smbalert_work(struct work_struct *work)
156{
157 struct i2c_smbus_alert *alert;
158
159 alert = container_of(work, struct i2c_smbus_alert, alert);
160
161 smbus_alert(irq: 0, d: alert);
162
163}
164
165/* Setup SMBALERT# infrastructure */
166static int smbalert_probe(struct i2c_client *ara)
167{
168 struct i2c_smbus_alert_setup *setup = dev_get_platdata(dev: &ara->dev);
169 struct i2c_smbus_alert *alert;
170 struct i2c_adapter *adapter = ara->adapter;
171 unsigned long irqflags = IRQF_SHARED | IRQF_ONESHOT;
172 struct gpio_desc *gpiod;
173 int res, irq;
174
175 alert = devm_kzalloc(dev: &ara->dev, size: sizeof(struct i2c_smbus_alert),
176 GFP_KERNEL);
177 if (!alert)
178 return -ENOMEM;
179
180 if (setup) {
181 irq = setup->irq;
182 } else {
183 irq = fwnode_irq_get_byname(dev_fwnode(adapter->dev.parent),
184 name: "smbus_alert");
185 if (irq <= 0) {
186 gpiod = devm_gpiod_get(dev: adapter->dev.parent, con_id: "smbalert", flags: GPIOD_IN);
187 if (IS_ERR(ptr: gpiod))
188 return PTR_ERR(ptr: gpiod);
189
190 irq = gpiod_to_irq(desc: gpiod);
191 if (irq <= 0)
192 return irq;
193
194 irqflags |= IRQF_TRIGGER_FALLING;
195 }
196 }
197
198 INIT_WORK(&alert->alert, smbalert_work);
199 alert->ara = ara;
200
201 if (irq > 0) {
202 res = devm_request_threaded_irq(dev: &ara->dev, irq, NULL, thread_fn: smbus_alert,
203 irqflags, devname: "smbus_alert", dev_id: alert);
204 if (res)
205 return res;
206 }
207
208 i2c_set_clientdata(client: ara, data: alert);
209 dev_info(&adapter->dev, "supports SMBALERT#\n");
210
211 return 0;
212}
213
214/* IRQ and memory resources are managed so they are freed automatically */
215static void smbalert_remove(struct i2c_client *ara)
216{
217 struct i2c_smbus_alert *alert = i2c_get_clientdata(client: ara);
218
219 cancel_work_sync(work: &alert->alert);
220}
221
222static const struct i2c_device_id smbalert_ids[] = {
223 { "smbus_alert" },
224 { /* LIST END */ }
225};
226MODULE_DEVICE_TABLE(i2c, smbalert_ids);
227
228static struct i2c_driver smbalert_driver = {
229 .driver = {
230 .name = "smbus_alert",
231 },
232 .probe = smbalert_probe,
233 .remove = smbalert_remove,
234 .id_table = smbalert_ids,
235};
236
237/**
238 * i2c_handle_smbus_alert - Handle an SMBus alert
239 * @ara: the ARA client on the relevant adapter
240 * Context: can't sleep
241 *
242 * Helper function to be called from an I2C bus driver's interrupt
243 * handler. It will schedule the alert work, in turn calling the
244 * corresponding I2C device driver's alert function.
245 *
246 * It is assumed that ara is a valid i2c client previously returned by
247 * i2c_new_smbus_alert_device().
248 */
249int i2c_handle_smbus_alert(struct i2c_client *ara)
250{
251 struct i2c_smbus_alert *alert = i2c_get_clientdata(client: ara);
252
253 return schedule_work(work: &alert->alert);
254}
255EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
256
257module_i2c_driver(smbalert_driver);
258
259#if IS_ENABLED(CONFIG_I2C_SLAVE)
260#define SMBUS_HOST_NOTIFY_LEN 3
261struct i2c_slave_host_notify_status {
262 u8 index;
263 u8 addr;
264};
265
266static int i2c_slave_host_notify_cb(struct i2c_client *client,
267 enum i2c_slave_event event, u8 *val)
268{
269 struct i2c_slave_host_notify_status *status = client->dev.platform_data;
270
271 switch (event) {
272 case I2C_SLAVE_WRITE_RECEIVED:
273 /* We only retrieve the first byte received (addr)
274 * since there is currently no support to retrieve the data
275 * parameter from the client.
276 */
277 if (status->index == 0)
278 status->addr = *val;
279 if (status->index < U8_MAX)
280 status->index++;
281 break;
282 case I2C_SLAVE_STOP:
283 if (status->index == SMBUS_HOST_NOTIFY_LEN)
284 i2c_handle_smbus_host_notify(client->adapter,
285 status->addr);
286 fallthrough;
287 case I2C_SLAVE_WRITE_REQUESTED:
288 status->index = 0;
289 break;
290 case I2C_SLAVE_READ_REQUESTED:
291 case I2C_SLAVE_READ_PROCESSED:
292 *val = 0xff;
293 break;
294 }
295
296 return 0;
297}
298
299/**
300 * i2c_new_slave_host_notify_device - get a client for SMBus host-notify support
301 * @adapter: the target adapter
302 * Context: can sleep
303 *
304 * Setup handling of the SMBus host-notify protocol on a given I2C bus segment.
305 *
306 * Handling is done by creating a device and its callback and handling data
307 * received via the SMBus host-notify address (0x8)
308 *
309 * This returns the client, which should be ultimately freed using
310 * i2c_free_slave_host_notify_device(); or an ERRPTR to indicate an error.
311 */
312struct i2c_client *i2c_new_slave_host_notify_device(struct i2c_adapter *adapter)
313{
314 struct i2c_board_info host_notify_board_info = {
315 I2C_BOARD_INFO("smbus_host_notify", 0x08),
316 .flags = I2C_CLIENT_SLAVE,
317 };
318 struct i2c_slave_host_notify_status *status;
319 struct i2c_client *client;
320 int ret;
321
322 status = kzalloc(sizeof(struct i2c_slave_host_notify_status),
323 GFP_KERNEL);
324 if (!status)
325 return ERR_PTR(-ENOMEM);
326
327 host_notify_board_info.platform_data = status;
328
329 client = i2c_new_client_device(adapter, &host_notify_board_info);
330 if (IS_ERR(client)) {
331 kfree(status);
332 return client;
333 }
334
335 ret = i2c_slave_register(client, i2c_slave_host_notify_cb);
336 if (ret) {
337 i2c_unregister_device(client);
338 kfree(status);
339 return ERR_PTR(ret);
340 }
341
342 return client;
343}
344EXPORT_SYMBOL_GPL(i2c_new_slave_host_notify_device);
345
346/**
347 * i2c_free_slave_host_notify_device - free the client for SMBus host-notify
348 * support
349 * @client: the client to free
350 * Context: can sleep
351 *
352 * Free the i2c_client allocated via i2c_new_slave_host_notify_device
353 */
354void i2c_free_slave_host_notify_device(struct i2c_client *client)
355{
356 if (IS_ERR_OR_NULL(client))
357 return;
358
359 i2c_slave_unregister(client);
360 kfree(client->dev.platform_data);
361 i2c_unregister_device(client);
362}
363EXPORT_SYMBOL_GPL(i2c_free_slave_host_notify_device);
364#endif
365
366/*
367 * SPD is not part of SMBus but we include it here for convenience as the
368 * target systems are the same.
369 * Restrictions to automatic SPD instantiation:
370 * - Only works if all filled slots have the same memory type
371 * - Only works for (LP)DDR memory types up to DDR5
372 * - Only works on systems with 1 to 8 memory slots
373 */
374#if IS_ENABLED(CONFIG_DMI)
375static void i2c_register_spd(struct i2c_adapter *adap, bool write_disabled)
376{
377 int n, slot_count = 0, dimm_count = 0;
378 u16 handle;
379 u8 common_mem_type = 0x0, mem_type;
380 u64 mem_size;
381 bool instantiate = true;
382 const char *name;
383
384 while ((handle = dmi_memdev_handle(slot: slot_count)) != 0xffff) {
385 slot_count++;
386
387 /* Skip empty slots */
388 mem_size = dmi_memdev_size(handle);
389 if (!mem_size)
390 continue;
391
392 /* Skip undefined memory type */
393 mem_type = dmi_memdev_type(handle);
394 if (mem_type <= 0x02) /* Invalid, Other, Unknown */
395 continue;
396
397 if (!common_mem_type) {
398 /* First filled slot */
399 common_mem_type = mem_type;
400 } else {
401 /* Check that all filled slots have the same type */
402 if (mem_type != common_mem_type) {
403 dev_warn(&adap->dev,
404 "Different memory types mixed, not instantiating SPD\n");
405 return;
406 }
407 }
408 dimm_count++;
409 }
410
411 /* No useful DMI data, bail out */
412 if (!dimm_count)
413 return;
414
415 /*
416 * The max number of SPD EEPROMs that can be addressed per bus is 8.
417 * If more slots are present either muxed or multiple busses are
418 * necessary or the additional slots are ignored.
419 */
420 slot_count = min(slot_count, 8);
421
422 /*
423 * Memory types could be found at section 7.18.2 (Memory Device — Type), table 78
424 * https://www.dmtf.org/sites/default/files/standards/documents/DSP0134_3.6.0.pdf
425 */
426 switch (common_mem_type) {
427 case 0x12: /* DDR */
428 case 0x13: /* DDR2 */
429 case 0x18: /* DDR3 */
430 case 0x1B: /* LPDDR */
431 case 0x1C: /* LPDDR2 */
432 case 0x1D: /* LPDDR3 */
433 name = "spd";
434 break;
435 case 0x1A: /* DDR4 */
436 case 0x1E: /* LPDDR4 */
437 name = "ee1004";
438 break;
439 case 0x22: /* DDR5 */
440 case 0x23: /* LPDDR5 */
441 name = "spd5118";
442 instantiate = !write_disabled;
443 break;
444 default:
445 dev_info(&adap->dev,
446 "Memory type 0x%02x not supported yet, not instantiating SPD\n",
447 common_mem_type);
448 return;
449 }
450
451 /*
452 * We don't know in which slots the memory modules are. We could
453 * try to guess from the slot names, but that would be rather complex
454 * and unreliable, so better probe all possible addresses until we
455 * have found all memory modules.
456 */
457 for (n = 0; n < slot_count && dimm_count; n++) {
458 struct i2c_board_info info;
459 unsigned short addr_list[2];
460
461 memset(s: &info, c: 0, n: sizeof(struct i2c_board_info));
462 strscpy(info.type, name, I2C_NAME_SIZE);
463 addr_list[0] = 0x50 + n;
464 addr_list[1] = I2C_CLIENT_END;
465
466 if (!instantiate)
467 continue;
468
469 if (!IS_ERR(ptr: i2c_new_scanned_device(adap, info: &info, addr_list, NULL))) {
470 dev_info(&adap->dev,
471 "Successfully instantiated SPD at 0x%hx\n",
472 addr_list[0]);
473 dimm_count--;
474 }
475 }
476}
477
478void i2c_register_spd_write_disable(struct i2c_adapter *adap)
479{
480 i2c_register_spd(adap, write_disabled: true);
481}
482EXPORT_SYMBOL_GPL(i2c_register_spd_write_disable);
483
484void i2c_register_spd_write_enable(struct i2c_adapter *adap)
485{
486 i2c_register_spd(adap, write_disabled: false);
487}
488EXPORT_SYMBOL_GPL(i2c_register_spd_write_enable);
489
490#endif
491
492MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
493MODULE_DESCRIPTION("SMBus protocol extensions support");
494MODULE_LICENSE("GPL");
495