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