1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * i2c-smbus.c - SMBus extensions to the I2C protocol
5 * Copyright (C) 2008 David Brownell
6 * Copyright (C) 2010-2019 Jean Delvare <jdelvare@suse.de>
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>
20 struct i2c_smbus_alert {
21 struct work_struct alert;
22 struct i2c_client *ara; /* Alert response address */
27 enum i2c_alert_protocol type;
31 /* If this is the alerting device, notify its driver */
32 static int smbus_do_alert(struct device *dev, void *addrp)
34 struct i2c_client *client = i2c_verify_client(dev);
35 struct alert_data *data = addrp;
36 struct i2c_driver *driver;
38 if (!client || client->addr != data->addr)
40 if (client->flags & I2C_CLIENT_TEN)
44 * Drivers should either disable alerts, or provide at least
45 * a minimal handler. Lock so the driver won't change.
48 if (client->dev.driver) {
49 driver = to_i2c_driver(client->dev.driver);
51 driver->alert(client, data->type, data->data);
53 dev_warn(&client->dev, "no driver alert()!\n");
55 dev_dbg(&client->dev, "alert with no driver\n");
58 /* Stop iterating after we find the device */
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.
66 static irqreturn_t smbus_alert(int irq, void *d)
68 struct i2c_smbus_alert *alert = d;
69 struct i2c_client *ara;
75 struct alert_data data;
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#.
82 * Note that SMBus 2.0 reserves 10-bit addresses for future
83 * use. We neither handle them, nor try to use PEC here.
85 status = i2c_smbus_read_byte(ara);
89 data.data = status & 1;
90 data.addr = status >> 1;
91 data.type = I2C_PROTOCOL_SMBUS_ALERT;
93 dev_dbg(&ara->dev, "SMBALERT# from dev 0x%02x, flag %d\n",
94 data.addr, data.data);
96 /* Notify driver for the device which issued the alert */
97 device_for_each_child(&ara->adapter->dev, &data,
104 static void smbalert_work(struct work_struct *work)
106 struct i2c_smbus_alert *alert;
108 alert = container_of(work, struct i2c_smbus_alert, alert);
110 smbus_alert(0, alert);
114 /* Setup SMBALERT# infrastructure */
115 static int smbalert_probe(struct i2c_client *ara,
116 const struct i2c_device_id *id)
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;
123 alert = devm_kzalloc(&ara->dev, sizeof(struct i2c_smbus_alert),
131 irq = of_irq_get_byname(adapter->dev.of_node, "smbus_alert");
136 INIT_WORK(&alert->alert, smbalert_work);
140 res = devm_request_threaded_irq(&ara->dev, irq,
142 IRQF_SHARED | IRQF_ONESHOT,
143 "smbus_alert", alert);
148 i2c_set_clientdata(ara, alert);
149 dev_info(&adapter->dev, "supports SMBALERT#\n");
154 /* IRQ and memory resources are managed so they are freed automatically */
155 static int smbalert_remove(struct i2c_client *ara)
157 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
159 cancel_work_sync(&alert->alert);
163 static const struct i2c_device_id smbalert_ids[] = {
164 { "smbus_alert", 0 },
167 MODULE_DEVICE_TABLE(i2c, smbalert_ids);
169 static struct i2c_driver smbalert_driver = {
171 .name = "smbus_alert",
173 .probe = smbalert_probe,
174 .remove = smbalert_remove,
175 .id_table = smbalert_ids,
179 * i2c_handle_smbus_alert - Handle an SMBus alert
180 * @ara: the ARA client on the relevant adapter
181 * Context: can't sleep
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.
187 * It is assumed that ara is a valid i2c client previously returned by
188 * i2c_new_smbus_alert_device().
190 int i2c_handle_smbus_alert(struct i2c_client *ara)
192 struct i2c_smbus_alert *alert = i2c_get_clientdata(ara);
194 return schedule_work(&alert->alert);
196 EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
198 module_i2c_driver(smbalert_driver);
201 * SPD is not part of SMBus but we include it here for convenience as the
202 * target systems are the same.
203 * Restrictions to automatic SPD instantiation:
204 * - Only works if all filled slots have the same memory type
205 * - Only works for DDR2, DDR3 and DDR4 for now
206 * - Only works on systems with 1 to 4 memory slots
208 #if IS_ENABLED(CONFIG_DMI)
209 void i2c_register_spd(struct i2c_adapter *adap)
211 int n, slot_count = 0, dimm_count = 0;
213 u8 common_mem_type = 0x0, mem_type;
217 while ((handle = dmi_memdev_handle(slot_count)) != 0xffff) {
220 /* Skip empty slots */
221 mem_size = dmi_memdev_size(handle);
225 /* Skip undefined memory type */
226 mem_type = dmi_memdev_type(handle);
227 if (mem_type <= 0x02) /* Invalid, Other, Unknown */
230 if (!common_mem_type) {
231 /* First filled slot */
232 common_mem_type = mem_type;
234 /* Check that all filled slots have the same type */
235 if (mem_type != common_mem_type) {
237 "Different memory types mixed, not instantiating SPD\n");
244 /* No useful DMI data, bail out */
248 dev_info(&adap->dev, "%d/%d memory slots populated (from DMI)\n",
249 dimm_count, slot_count);
251 if (slot_count > 4) {
253 "Systems with more than 4 memory slots not supported yet, not instantiating SPD\n");
257 switch (common_mem_type) {
258 case 0x13: /* DDR2 */
259 case 0x18: /* DDR3 */
260 case 0x1C: /* LPDDR2 */
261 case 0x1D: /* LPDDR3 */
264 case 0x1A: /* DDR4 */
265 case 0x1E: /* LPDDR4 */
270 "Memory type 0x%02x not supported yet, not instantiating SPD\n",
276 * We don't know in which slots the memory modules are. We could
277 * try to guess from the slot names, but that would be rather complex
278 * and unreliable, so better probe all possible addresses until we
279 * have found all memory modules.
281 for (n = 0; n < slot_count && dimm_count; n++) {
282 struct i2c_board_info info;
283 unsigned short addr_list[2];
285 memset(&info, 0, sizeof(struct i2c_board_info));
286 strlcpy(info.type, name, I2C_NAME_SIZE);
287 addr_list[0] = 0x50 + n;
288 addr_list[1] = I2C_CLIENT_END;
290 if (!IS_ERR(i2c_new_scanned_device(adap, &info, addr_list, NULL))) {
292 "Successfully instantiated SPD at 0x%hx\n",
298 EXPORT_SYMBOL_GPL(i2c_register_spd);
301 MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
302 MODULE_DESCRIPTION("SMBus protocol extensions support");
303 MODULE_LICENSE("GPL");