drivers/i2c/i2c-smbus.c

   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 */
  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  */
  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
 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 */
 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 */
 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  */
 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
 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  */
 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  */
 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)
 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");