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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(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(&ara->adapter->dev, &data,
132 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(&ara->adapter->dev, &data,
146 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(0, 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(&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(&ara->dev, 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 "smbus_alert");
185 if (irq <= 0) {
186 gpiod = devm_gpiod_get(adapter->dev.parent, "smbalert", GPIOD_IN);
187 if (IS_ERR(gpiod))
188 return PTR_ERR(gpiod);
189
190 irq = gpiod_to_irq(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(&ara->dev, irq, NULL, smbus_alert,
203 irqflags, "smbus_alert", alert);
204 if (res)
205 return res;
206 }
207
208 i2c_set_clientdata(ara, 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(ara);
218
219 cancel_work_sync(&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(ara);
252
253 return schedule_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)
375void i2c_register_spd(struct i2c_adapter *adap)
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 const char *name;
382
383 while ((handle = dmi_memdev_handle(slot_count)) != 0xffff) {
384 slot_count++;
385
386 /* Skip empty slots */
387 mem_size = dmi_memdev_size(handle);
388 if (!mem_size)
389 continue;
390
391 /* Skip undefined memory type */
392 mem_type = dmi_memdev_type(handle);
393 if (mem_type <= 0x02) /* Invalid, Other, Unknown */
394 continue;
395
396 if (!common_mem_type) {
397 /* First filled slot */
398 common_mem_type = mem_type;
399 } else {
400 /* Check that all filled slots have the same type */
401 if (mem_type != common_mem_type) {
402 dev_warn(&adap->dev,
403 "Different memory types mixed, not instantiating SPD\n");
404 return;
405 }
406 }
407 dimm_count++;
408 }
409
410 /* No useful DMI data, bail out */
411 if (!dimm_count)
412 return;
413
414 /*
415 * The max number of SPD EEPROMs that can be addressed per bus is 8.
416 * If more slots are present either muxed or multiple busses are
417 * necessary or the additional slots are ignored.
418 */
419 slot_count = min(slot_count, 8);
420
421 /*
422 * Memory types could be found at section 7.18.2 (Memory Device — Type), table 78
423 * https://www.dmtf.org/sites/default/files/standards/documents/DSP0134_3.6.0.pdf
424 */
425 switch (common_mem_type) {
426 case 0x12: /* DDR */
427 case 0x13: /* DDR2 */
428 case 0x18: /* DDR3 */
429 case 0x1B: /* LPDDR */
430 case 0x1C: /* LPDDR2 */
431 case 0x1D: /* LPDDR3 */
432 name = "spd";
433 break;
434 case 0x1A: /* DDR4 */
435 case 0x1E: /* LPDDR4 */
436 name = "ee1004";
437 break;
438 case 0x22: /* DDR5 */
439 case 0x23: /* LPDDR5 */
440 name = "spd5118";
441 break;
442 default:
443 dev_info(&adap->dev,
444 "Memory type 0x%02x not supported yet, not instantiating SPD\n",
445 common_mem_type);
446 return;
447 }
448
449 /*
450 * We don't know in which slots the memory modules are. We could
451 * try to guess from the slot names, but that would be rather complex
452 * and unreliable, so better probe all possible addresses until we
453 * have found all memory modules.
454 */
455 for (n = 0; n < slot_count && dimm_count; n++) {
456 struct i2c_board_info info;
457 unsigned short addr_list[2];
458
459 memset(&info, 0, sizeof(struct i2c_board_info));
460 strscpy(info.type, name, I2C_NAME_SIZE);
461 addr_list[0] = 0x50 + n;
462 addr_list[1] = I2C_CLIENT_END;
463
464 if (!IS_ERR(i2c_new_scanned_device(adap, &info, addr_list, NULL))) {
465 dev_info(&adap->dev,
466 "Successfully instantiated SPD at 0x%hx\n",
467 addr_list[0]);
468 dimm_count--;
469 }
470 }
471}
472EXPORT_SYMBOL_GPL(i2c_register_spd);
473#endif
474
475MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
476MODULE_DESCRIPTION("SMBus protocol extensions support");
477MODULE_LICENSE("GPL");
1/*
2 * i2c-smbus.c - SMBus extensions to the I2C protocol
3 *
4 * Copyright (C) 2008 David Brownell
5 * Copyright (C) 2010 Jean Delvare <jdelvare@suse.de>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 */
17
18#include <linux/device.h>
19#include <linux/i2c.h>
20#include <linux/i2c-smbus.h>
21#include <linux/interrupt.h>
22#include <linux/kernel.h>
23#include <linux/module.h>
24#include <linux/slab.h>
25#include <linux/workqueue.h>
26
27struct i2c_smbus_alert {
28 unsigned int alert_edge_triggered:1;
29 int irq;
30 struct work_struct alert;
31 struct i2c_client *ara; /* Alert response address */
32};
33
34struct alert_data {
35 unsigned short addr;
36 u8 flag:1;
37};
38
39/* If this is the alerting device, notify its driver */
40static int smbus_do_alert(struct device *dev, void *addrp)
41{
42 struct i2c_client *client = i2c_verify_client(dev);
43 struct alert_data *data = addrp;
44 struct i2c_driver *driver;
45
46 if (!client || client->addr != data->addr)
47 return 0;
48 if (client->flags & I2C_CLIENT_TEN)
49 return 0;
50
51 /*
52 * Drivers should either disable alerts, or provide at least
53 * a minimal handler. Lock so the driver won't change.
54 */
55 device_lock(dev);
56 if (client->dev.driver) {
57 driver = to_i2c_driver(client->dev.driver);
58 if (driver->alert)
59 driver->alert(client, data->flag);
60 else
61 dev_warn(&client->dev, "no driver alert()!\n");
62 } else
63 dev_dbg(&client->dev, "alert with no driver\n");
64 device_unlock(dev);
65
66 /* Stop iterating after we find the device */
67 return -EBUSY;
68}
69
70/*
71 * The alert IRQ handler needs to hand work off to a task which can issue
72 * SMBus calls, because those sleeping calls can't be made in IRQ context.
73 */
74static void smbus_alert(struct work_struct *work)
75{
76 struct i2c_smbus_alert *alert;
77 struct i2c_client *ara;
78 unsigned short prev_addr = 0; /* Not a valid address */
79
80 alert = container_of(work, struct i2c_smbus_alert, alert);
81 ara = alert->ara;
82
83 for (;;) {
84 s32 status;
85 struct alert_data data;
86
87 /*
88 * Devices with pending alerts reply in address order, low
89 * to high, because of slave transmit arbitration. After
90 * responding, an SMBus device stops asserting SMBALERT#.
91 *
92 * Note that SMBus 2.0 reserves 10-bit addresses for future
93 * use. We neither handle them, nor try to use PEC here.
94 */
95 status = i2c_smbus_read_byte(ara);
96 if (status < 0)
97 break;
98
99 data.flag = status & 1;
100 data.addr = status >> 1;
101
102 if (data.addr == prev_addr) {
103 dev_warn(&ara->dev, "Duplicate SMBALERT# from dev "
104 "0x%02x, skipping\n", data.addr);
105 break;
106 }
107 dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n",
108 data.addr, data.flag);
109
110 /* Notify driver for the device which issued the alert */
111 device_for_each_child(&ara->adapter->dev, &data,
112 smbus_do_alert);
113 prev_addr = data.addr;
114 }
115
116 /* We handled all alerts; re-enable level-triggered IRQs */
117 if (!alert->alert_edge_triggered)
118 enable_irq(alert->irq);
119}
120
121static irqreturn_t smbalert_irq(int irq, void *d)
122{
123 struct i2c_smbus_alert *alert = d;
124
125 /* Disable level-triggered IRQs until we handle them */
126 if (!alert->alert_edge_triggered)
127 disable_irq_nosync(irq);
128
129 schedule_work(&alert->alert);
130 return IRQ_HANDLED;
131}
132
133/* Setup SMBALERT# infrastructure */
134static int smbalert_probe(struct i2c_client *ara,
135 const struct i2c_device_id *id)
136{
137 struct i2c_smbus_alert_setup *setup = dev_get_platdata(&ara->dev);
138 struct i2c_smbus_alert *alert;
139 struct i2c_adapter *adapter = ara->adapter;
140 int res;
141
142 alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert),
143 GFP_KERNEL);
144 if (!alert)
145 return -ENOMEM;
146
147 alert->alert_edge_triggered = setup->alert_edge_triggered;
148 alert->irq = setup->irq;
149 INIT_WORK(&alert->alert, smbus_alert);
150 alert->ara = ara;
151
152 if (setup->irq > 0) {
153 res = devm_request_irq(&ara->dev, setup->irq, smbalert_irq,
154 0, "smbus_alert", alert);
155 if (res)
156 return res;
157 }
158
159 i2c_set_clientdata(ara, alert);
160 dev_info(&adapter->dev, "supports SMBALERT#, %s trigger\n",
161 setup->alert_edge_triggered ? "edge" : "level");
162
163 return 0;
164}
165
166/* IRQ and memory resources are managed so they are freed automatically */
167static int smbalert_remove(struct i2c_client *ara)
168{
169 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
170
171 cancel_work_sync(&alert->alert);
172 return 0;
173}
174
175static const struct i2c_device_id smbalert_ids[] = {
176 { "smbus_alert", 0 },
177 { /* LIST END */ }
178};
179MODULE_DEVICE_TABLE(i2c, smbalert_ids);
180
181static struct i2c_driver smbalert_driver = {
182 .driver = {
183 .name = "smbus_alert",
184 },
185 .probe = smbalert_probe,
186 .remove = smbalert_remove,
187 .id_table = smbalert_ids,
188};
189
190/**
191 * i2c_setup_smbus_alert - Setup SMBus alert support
192 * @adapter: the target adapter
193 * @setup: setup data for the SMBus alert handler
194 * Context: can sleep
195 *
196 * Setup handling of the SMBus alert protocol on a given I2C bus segment.
197 *
198 * Handling can be done either through our IRQ handler, or by the
199 * adapter (from its handler, periodic polling, or whatever).
200 *
201 * NOTE that if we manage the IRQ, we *MUST* know if it's level or
202 * edge triggered in order to hand it to the workqueue correctly.
203 * If triggering the alert seems to wedge the system, you probably
204 * should have said it's level triggered.
205 *
206 * This returns the ara client, which should be saved for later use with
207 * i2c_handle_smbus_alert() and ultimately i2c_unregister_device(); or NULL
208 * to indicate an error.
209 */
210struct i2c_client *i2c_setup_smbus_alert(struct i2c_adapter *adapter,
211 struct i2c_smbus_alert_setup *setup)
212{
213 struct i2c_board_info ara_board_info = {
214 I2C_BOARD_INFO("smbus_alert", 0x0c),
215 .platform_data = setup,
216 };
217
218 return i2c_new_device(adapter, &ara_board_info);
219}
220EXPORT_SYMBOL_GPL(i2c_setup_smbus_alert);
221
222/**
223 * i2c_handle_smbus_alert - Handle an SMBus alert
224 * @ara: the ARA client on the relevant adapter
225 * Context: can't sleep
226 *
227 * Helper function to be called from an I2C bus driver's interrupt
228 * handler. It will schedule the alert work, in turn calling the
229 * corresponding I2C device driver's alert function.
230 *
231 * It is assumed that ara is a valid i2c client previously returned by
232 * i2c_setup_smbus_alert().
233 */
234int i2c_handle_smbus_alert(struct i2c_client *ara)
235{
236 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
237
238 return schedule_work(&alert->alert);
239}
240EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
241
242module_i2c_driver(smbalert_driver);
243
244MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
245MODULE_DESCRIPTION("SMBus protocol extensions support");
246MODULE_LICENSE("GPL");