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
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
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 */
smbus_alert(int irq,void * d)66 static 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
smbalert_work(struct work_struct * work)104 static 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 */
smbalert_probe(struct i2c_client * ara,const struct i2c_device_id * id)115 static 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 */
smbalert_remove(struct i2c_client * ara)155 static 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
163 static const struct i2c_device_id smbalert_ids[] = {
164 { "smbus_alert", 0 },
165 { /* LIST END */ }
166 };
167 MODULE_DEVICE_TABLE(i2c, smbalert_ids);
168
169 static 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 */
i2c_handle_smbus_alert(struct i2c_client * ara)190 int 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 }
196 EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
197
198 module_i2c_driver(smbalert_driver);
199
200 #if IS_ENABLED(CONFIG_I2C_SLAVE)
201 #define SMBUS_HOST_NOTIFY_LEN 3
202 struct i2c_slave_host_notify_status {
203 u8 index;
204 u8 addr;
205 };
206
i2c_slave_host_notify_cb(struct i2c_client * client,enum i2c_slave_event event,u8 * val)207 static 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 */
i2c_new_slave_host_notify_device(struct i2c_adapter * adapter)253 struct 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 }
285 EXPORT_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 */
i2c_free_slave_host_notify_device(struct i2c_client * client)295 void 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 }
304 EXPORT_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)
i2c_register_spd(struct i2c_adapter * adap)316 void 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 }
405 EXPORT_SYMBOL_GPL(i2c_register_spd);
406 #endif
407
408 MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
409 MODULE_DESCRIPTION("SMBus protocol extensions support");
410 MODULE_LICENSE("GPL");
411