drivers/char/ipmi/ipmi_kcs_sm.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * ipmi_kcs_sm.c
   4  *
   5  * State machine for handling IPMI KCS interfaces.
   6  *
   7  * Author: MontaVista Software, Inc.
   8  *         Corey Minyard <minyard@mvista.com>
   9  *         source@mvista.com
  10  *
  11  * Copyright 2002 MontaVista Software Inc.
  12  */
  13
  14 /*
  15  * This state machine is taken from the state machine in the IPMI spec,
  16  * pretty much verbatim.  If you have questions about the states, see
  17  * that document.
  18  */
  19
  20 #define DEBUG /* So dev_dbg() is always available. */
  21
  22 #include <linux/kernel.h> /* For printk. */
  23 #include <linux/module.h>
  24 #include <linux/moduleparam.h>
  25 #include <linux/string.h>
  26 #include <linux/jiffies.h>
  27 #include <linux/ipmi_msgdefs.h>         /* for completion codes */
  28 #include "ipmi_si_sm.h"
  29
  30 /* kcs_debug is a bit-field
  31  *      KCS_DEBUG_ENABLE -      turned on for now
  32  *      KCS_DEBUG_MSG    -      commands and their responses
  33  *      KCS_DEBUG_STATES -      state machine
  34  */
  35 #define KCS_DEBUG_STATES        4
  36 #define KCS_DEBUG_MSG           2
  37 #define KCS_DEBUG_ENABLE        1
  38
  39 static int kcs_debug;
  40 module_param(kcs_debug, int, 0644);
  41 MODULE_PARM_DESC(kcs_debug, "debug bitmask, 1=enable, 2=messages, 4=states");
  42
  43 /* The states the KCS driver may be in. */
  44 enum kcs_states {
  45         /* The KCS interface is currently doing nothing. */
  46         KCS_IDLE,
  47
  48         /*
  49          * We are starting an operation.  The data is in the output
  50          * buffer, but nothing has been done to the interface yet.  This
  51          * was added to the state machine in the spec to wait for the
  52          * initial IBF.
  53          */
  54         KCS_START_OP,
  55
  56         /* We have written a write cmd to the interface. */
  57         KCS_WAIT_WRITE_START,
  58
  59         /* We are writing bytes to the interface. */
  60         KCS_WAIT_WRITE,
  61
  62         /*
  63          * We have written the write end cmd to the interface, and
  64          * still need to write the last byte.
  65          */
  66         KCS_WAIT_WRITE_END,
  67
  68         /* We are waiting to read data from the interface. */
  69         KCS_WAIT_READ,
  70
  71         /*
  72          * State to transition to the error handler, this was added to
  73          * the state machine in the spec to be sure IBF was there.
  74          */
  75         KCS_ERROR0,
  76
  77         /*
  78          * First stage error handler, wait for the interface to
  79          * respond.
  80          */
  81         KCS_ERROR1,
  82
  83         /*
  84          * The abort cmd has been written, wait for the interface to
  85          * respond.
  86          */
  87         KCS_ERROR2,
  88
  89         /*
  90          * We wrote some data to the interface, wait for it to switch
  91          * to read mode.
  92          */
  93         KCS_ERROR3,
  94
  95         /* The hardware failed to follow the state machine. */
  96         KCS_HOSED
  97 };
  98
  99 #define MAX_KCS_READ_SIZE IPMI_MAX_MSG_LENGTH
 100 #define MAX_KCS_WRITE_SIZE IPMI_MAX_MSG_LENGTH
 101
 102 /* Timeouts in microseconds. */
 103 #define IBF_RETRY_TIMEOUT (5*USEC_PER_SEC)
 104 #define OBF_RETRY_TIMEOUT (5*USEC_PER_SEC)
 105 #define MAX_ERROR_RETRIES 10
 106 #define ERROR0_OBF_WAIT_JIFFIES (2*HZ)
 107
 108 struct si_sm_data {
 109         enum kcs_states  state;
 110         struct si_sm_io *io;
 111         unsigned char    write_data[MAX_KCS_WRITE_SIZE];
 112         int              write_pos;
 113         int              write_count;
 114         int              orig_write_count;
 115         unsigned char    read_data[MAX_KCS_READ_SIZE];
 116         int              read_pos;
 117         int              truncated;
 118
 119         unsigned int  error_retries;
 120         long          ibf_timeout;
 121         long          obf_timeout;
 122         unsigned long  error0_timeout;
 123 };
 124
 125 static unsigned int init_kcs_data_with_state(struct si_sm_data *kcs,
 126                                   struct si_sm_io *io, enum kcs_states state)
 127 {
 128         kcs->state = state;
 129         kcs->io = io;
 130         kcs->write_pos = 0;
 131         kcs->write_count = 0;
 132         kcs->orig_write_count = 0;
 133         kcs->read_pos = 0;
 134         kcs->error_retries = 0;
 135         kcs->truncated = 0;
 136         kcs->ibf_timeout = IBF_RETRY_TIMEOUT;
 137         kcs->obf_timeout = OBF_RETRY_TIMEOUT;
 138
 139         /* Reserve 2 I/O bytes. */
 140         return 2;
 141 }
 142
 143 static unsigned int init_kcs_data(struct si_sm_data *kcs,
 144                                   struct si_sm_io *io)
 145 {
 146         return init_kcs_data_with_state(kcs, io, KCS_IDLE);
 147 }
 148
 149 static inline unsigned char read_status(struct si_sm_data *kcs)
 150 {
 151         return kcs->io->inputb(kcs->io, 1);
 152 }
 153
 154 static inline unsigned char read_data(struct si_sm_data *kcs)
 155 {
 156         return kcs->io->inputb(kcs->io, 0);
 157 }
 158
 159 static inline void write_cmd(struct si_sm_data *kcs, unsigned char data)
 160 {
 161         kcs->io->outputb(kcs->io, 1, data);
 162 }
 163
 164 static inline void write_data(struct si_sm_data *kcs, unsigned char data)
 165 {
 166         kcs->io->outputb(kcs->io, 0, data);
 167 }
 168
 169 /* Control codes. */
 170 #define KCS_GET_STATUS_ABORT    0x60
 171 #define KCS_WRITE_START         0x61
 172 #define KCS_WRITE_END           0x62
 173 #define KCS_READ_BYTE           0x68
 174
 175 /* Status bits. */
 176 #define GET_STATUS_STATE(status) (((status) >> 6) & 0x03)
 177 #define KCS_IDLE_STATE  0
 178 #define KCS_READ_STATE  1
 179 #define KCS_WRITE_STATE 2
 180 #define KCS_ERROR_STATE 3
 181 #define GET_STATUS_ATN(status) ((status) & 0x04)
 182 #define GET_STATUS_IBF(status) ((status) & 0x02)
 183 #define GET_STATUS_OBF(status) ((status) & 0x01)
 184
 185
 186 static inline void write_next_byte(struct si_sm_data *kcs)
 187 {
 188         write_data(kcs, kcs->write_data[kcs->write_pos]);
 189         (kcs->write_pos)++;
 190         (kcs->write_count)--;
 191 }
 192
 193 static inline void start_error_recovery(struct si_sm_data *kcs, char *reason)
 194 {
 195         (kcs->error_retries)++;
 196         if (kcs->error_retries > MAX_ERROR_RETRIES) {
 197                 if (kcs_debug & KCS_DEBUG_ENABLE)
 198                         dev_dbg(kcs->io->dev, "ipmi_kcs_sm: kcs hosed: %s\n",
 199                                 reason);
 200                 kcs->state = KCS_HOSED;
 201         } else {
 202                 kcs->error0_timeout = jiffies + ERROR0_OBF_WAIT_JIFFIES;
 203                 kcs->state = KCS_ERROR0;
 204         }
 205 }
 206
 207 static inline void read_next_byte(struct si_sm_data *kcs)
 208 {
 209         if (kcs->read_pos >= MAX_KCS_READ_SIZE) {
 210                 /* Throw the data away and mark it truncated. */
 211                 read_data(kcs);
 212                 kcs->truncated = 1;
 213         } else {
 214                 kcs->read_data[kcs->read_pos] = read_data(kcs);
 215                 (kcs->read_pos)++;
 216         }
 217         write_data(kcs, KCS_READ_BYTE);
 218 }
 219
 220 static inline int check_ibf(struct si_sm_data *kcs, unsigned char status,
 221                             long time)
 222 {
 223         if (GET_STATUS_IBF(status)) {
 224                 kcs->ibf_timeout -= time;
 225                 if (kcs->ibf_timeout < 0) {
 226                         start_error_recovery(kcs, "IBF not ready in time");
 227                         kcs->ibf_timeout = IBF_RETRY_TIMEOUT;
 228                         return 1;
 229                 }
 230                 return 0;
 231         }
 232         kcs->ibf_timeout = IBF_RETRY_TIMEOUT;
 233         return 1;
 234 }
 235
 236 static inline int check_obf(struct si_sm_data *kcs, unsigned char status,
 237                             long time)
 238 {
 239         if (!GET_STATUS_OBF(status)) {
 240                 kcs->obf_timeout -= time;
 241                 if (kcs->obf_timeout < 0) {
 242                         kcs->obf_timeout = OBF_RETRY_TIMEOUT;
 243                         start_error_recovery(kcs, "OBF not ready in time");
 244                         return 1;
 245                 }
 246                 return 0;
 247         }
 248         kcs->obf_timeout = OBF_RETRY_TIMEOUT;
 249         return 1;
 250 }
 251
 252 static void clear_obf(struct si_sm_data *kcs, unsigned char status)
 253 {
 254         if (GET_STATUS_OBF(status))
 255                 read_data(kcs);
 256 }
 257
 258 static void restart_kcs_transaction(struct si_sm_data *kcs)
 259 {
 260         kcs->write_count = kcs->orig_write_count;
 261         kcs->write_pos = 0;
 262         kcs->read_pos = 0;
 263         kcs->state = KCS_WAIT_WRITE_START;
 264         kcs->ibf_timeout = IBF_RETRY_TIMEOUT;
 265         kcs->obf_timeout = OBF_RETRY_TIMEOUT;
 266         write_cmd(kcs, KCS_WRITE_START);
 267 }
 268
 269 static int start_kcs_transaction(struct si_sm_data *kcs, unsigned char *data,
 270                                  unsigned int size)
 271 {
 272         unsigned int i;
 273
 274         if (size < 2)
 275                 return IPMI_REQ_LEN_INVALID_ERR;
 276         if (size > MAX_KCS_WRITE_SIZE)
 277                 return IPMI_REQ_LEN_EXCEEDED_ERR;
 278
 279         if (kcs->state != KCS_IDLE) {
 280                 dev_warn(kcs->io->dev, "KCS in invalid state %d\n", kcs->state);
 281                 return IPMI_NOT_IN_MY_STATE_ERR;
 282         }
 283
 284         if (kcs_debug & KCS_DEBUG_MSG) {
 285                 dev_dbg(kcs->io->dev, "%s -", __func__);
 286                 for (i = 0; i < size; i++)
 287                         pr_cont(" %02x", data[i]);
 288                 pr_cont("\n");
 289         }
 290         kcs->error_retries = 0;
 291         memcpy(kcs->write_data, data, size);
 292         kcs->write_count = size;
 293         kcs->orig_write_count = size;
 294         kcs->write_pos = 0;
 295         kcs->read_pos = 0;
 296         kcs->state = KCS_START_OP;
 297         kcs->ibf_timeout = IBF_RETRY_TIMEOUT;
 298         kcs->obf_timeout = OBF_RETRY_TIMEOUT;
 299         return 0;
 300 }
 301
 302 static int get_kcs_result(struct si_sm_data *kcs, unsigned char *data,
 303                           unsigned int length)
 304 {
 305         if (length < kcs->read_pos) {
 306                 kcs->read_pos = length;
 307                 kcs->truncated = 1;
 308         }
 309
 310         memcpy(data, kcs->read_data, kcs->read_pos);
 311
 312         if ((length >= 3) && (kcs->read_pos < 3)) {
 313                 /* Guarantee that we return at least 3 bytes, with an
 314                    error in the third byte if it is too short. */
 315                 data[2] = IPMI_ERR_UNSPECIFIED;
 316                 kcs->read_pos = 3;
 317         }
 318         if (kcs->truncated) {
 319                 /*
 320                  * Report a truncated error.  We might overwrite
 321                  * another error, but that's too bad, the user needs
 322                  * to know it was truncated.
 323                  */
 324                 data[2] = IPMI_ERR_MSG_TRUNCATED;
 325                 kcs->truncated = 0;
 326         }
 327
 328         return kcs->read_pos;
 329 }
 330
 331 /*
 332  * This implements the state machine defined in the IPMI manual, see
 333  * that for details on how this works.  Divide that flowchart into
 334  * sections delimited by "Wait for IBF" and this will become clear.
 335  */
 336 static enum si_sm_result kcs_event(struct si_sm_data *kcs, long time)
 337 {
 338         unsigned char status;
 339         unsigned char state;
 340
 341         status = read_status(kcs);
 342
 343         if (kcs_debug & KCS_DEBUG_STATES)
 344                 dev_dbg(kcs->io->dev,
 345                         "KCS: State = %d, %x\n", kcs->state, status);
 346
 347         /* All states wait for ibf, so just do it here. */
 348         if (!check_ibf(kcs, status, time))
 349                 return SI_SM_CALL_WITH_DELAY;
 350
 351         /* Just about everything looks at the KCS state, so grab that, too. */
 352         state = GET_STATUS_STATE(status);
 353
 354         switch (kcs->state) {
 355         case KCS_IDLE:
 356                 /* If there's and interrupt source, turn it off. */
 357                 clear_obf(kcs, status);
 358
 359                 if (GET_STATUS_ATN(status))
 360                         return SI_SM_ATTN;
 361                 else
 362                         return SI_SM_IDLE;
 363
 364         case KCS_START_OP:
 365                 if (state != KCS_IDLE_STATE) {
 366                         start_error_recovery(kcs,
 367                                              "State machine not idle at start");
 368                         break;
 369                 }
 370
 371                 clear_obf(kcs, status);
 372                 write_cmd(kcs, KCS_WRITE_START);
 373                 kcs->state = KCS_WAIT_WRITE_START;
 374                 break;
 375
 376         case KCS_WAIT_WRITE_START:
 377                 if (state != KCS_WRITE_STATE) {
 378                         start_error_recovery(
 379                                 kcs,
 380                                 "Not in write state at write start");
 381                         break;
 382                 }
 383                 read_data(kcs);
 384                 if (kcs->write_count == 1) {
 385                         write_cmd(kcs, KCS_WRITE_END);
 386                         kcs->state = KCS_WAIT_WRITE_END;
 387                 } else {
 388                         write_next_byte(kcs);
 389                         kcs->state = KCS_WAIT_WRITE;
 390                 }
 391                 break;
 392
 393         case KCS_WAIT_WRITE:
 394                 if (state != KCS_WRITE_STATE) {
 395                         start_error_recovery(kcs,
 396                                              "Not in write state for write");
 397                         break;
 398                 }
 399                 clear_obf(kcs, status);
 400                 if (kcs->write_count == 1) {
 401                         write_cmd(kcs, KCS_WRITE_END);
 402                         kcs->state = KCS_WAIT_WRITE_END;
 403                 } else {
 404                         write_next_byte(kcs);
 405                 }
 406                 break;
 407
 408         case KCS_WAIT_WRITE_END:
 409                 if (state != KCS_WRITE_STATE) {
 410                         start_error_recovery(kcs,
 411                                              "Not in write state"
 412                                              " for write end");
 413                         break;
 414                 }
 415                 clear_obf(kcs, status);
 416                 write_next_byte(kcs);
 417                 kcs->state = KCS_WAIT_READ;
 418                 break;
 419
 420         case KCS_WAIT_READ:
 421                 if ((state != KCS_READ_STATE) && (state != KCS_IDLE_STATE)) {
 422                         start_error_recovery(
 423                                 kcs,
 424                                 "Not in read or idle in read state");
 425                         break;
 426                 }
 427
 428                 if (state == KCS_READ_STATE) {
 429                         if (!check_obf(kcs, status, time))
 430                                 return SI_SM_CALL_WITH_DELAY;
 431                         read_next_byte(kcs);
 432                 } else {
 433                         /*
 434                          * We don't implement this exactly like the state
 435                          * machine in the spec.  Some broken hardware
 436                          * does not write the final dummy byte to the
 437                          * read register.  Thus obf will never go high
 438                          * here.  We just go straight to idle, and we
 439                          * handle clearing out obf in idle state if it
 440                          * happens to come in.
 441                          */
 442                         clear_obf(kcs, status);
 443                         kcs->orig_write_count = 0;
 444                         kcs->state = KCS_IDLE;
 445                         return SI_SM_TRANSACTION_COMPLETE;
 446                 }
 447                 break;
 448
 449         case KCS_ERROR0:
 450                 clear_obf(kcs, status);
 451                 status = read_status(kcs);
 452                 if (GET_STATUS_OBF(status))
 453                         /* controller isn't responding */
 454                         if (time_before(jiffies, kcs->error0_timeout))
 455                                 return SI_SM_CALL_WITH_TICK_DELAY;
 456                 write_cmd(kcs, KCS_GET_STATUS_ABORT);
 457                 kcs->state = KCS_ERROR1;
 458                 break;
 459
 460         case KCS_ERROR1:
 461                 clear_obf(kcs, status);
 462                 write_data(kcs, 0);
 463                 kcs->state = KCS_ERROR2;
 464                 break;
 465
 466         case KCS_ERROR2:
 467                 if (state != KCS_READ_STATE) {
 468                         start_error_recovery(kcs,
 469                                              "Not in read state for error2");
 470                         break;
 471                 }
 472                 if (!check_obf(kcs, status, time))
 473                         return SI_SM_CALL_WITH_DELAY;
 474
 475                 clear_obf(kcs, status);
 476                 write_data(kcs, KCS_READ_BYTE);
 477                 kcs->state = KCS_ERROR3;
 478                 break;
 479
 480         case KCS_ERROR3:
 481                 if (state != KCS_IDLE_STATE) {
 482                         start_error_recovery(kcs,
 483                                              "Not in idle state for error3");
 484                         break;
 485                 }
 486
 487                 if (!check_obf(kcs, status, time))
 488                         return SI_SM_CALL_WITH_DELAY;
 489
 490                 clear_obf(kcs, status);
 491                 if (kcs->orig_write_count) {
 492                         restart_kcs_transaction(kcs);
 493                 } else {
 494                         kcs->state = KCS_IDLE;
 495                         return SI_SM_TRANSACTION_COMPLETE;
 496                 }
 497                 break;
 498
 499         case KCS_HOSED:
 500                 break;
 501         }
 502
 503         if (kcs->state == KCS_HOSED) {
 504                 init_kcs_data_with_state(kcs, kcs->io, KCS_ERROR0);
 505                 return SI_SM_HOSED;
 506         }
 507
 508         return SI_SM_CALL_WITHOUT_DELAY;
 509 }
 510
 511 static int kcs_size(void)
 512 {
 513         return sizeof(struct si_sm_data);
 514 }
 515
 516 static int kcs_detect(struct si_sm_data *kcs)
 517 {
 518         /*
 519          * It's impossible for the KCS status register to be all 1's,
 520          * (assuming a properly functioning, self-initialized BMC)
 521          * but that's what you get from reading a bogus address, so we
 522          * test that first.
 523          */
 524         if (read_status(kcs) == 0xff)
 525                 return 1;
 526
 527         return 0;
 528 }
 529
 530 static void kcs_cleanup(struct si_sm_data *kcs)
 531 {
 532 }
 533
 534 const struct si_sm_handlers kcs_smi_handlers = {
 535         .init_data         = init_kcs_data,
 536         .start_transaction = start_kcs_transaction,
 537         .get_result        = get_kcs_result,
 538         .event             = kcs_event,
 539         .detect            = kcs_detect,
 540         .cleanup           = kcs_cleanup,
 541         .size              = kcs_size,
 542 };