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