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(struct si_sm_data *kcs,
 126                                   struct si_sm_io *io)
 127 {
 128         kcs->state = KCS_IDLE;
 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 inline unsigned char read_status(struct si_sm_data *kcs)
 144 {
 145         return kcs->io->inputb(kcs->io, 1);
 146 }
 147
 148 static inline unsigned char read_data(struct si_sm_data *kcs)
 149 {
 150         return kcs->io->inputb(kcs->io, 0);
 151 }
 152
 153 static inline void write_cmd(struct si_sm_data *kcs, unsigned char data)
 154 {
 155         kcs->io->outputb(kcs->io, 1, data);
 156 }
 157
 158 static inline void write_data(struct si_sm_data *kcs, unsigned char data)
 159 {
 160         kcs->io->outputb(kcs->io, 0, data);
 161 }
 162
 163 /* Control codes. */
 164 #define KCS_GET_STATUS_ABORT    0x60
 165 #define KCS_WRITE_START         0x61
 166 #define KCS_WRITE_END           0x62
 167 #define KCS_READ_BYTE           0x68
 168
 169 /* Status bits. */
 170 #define GET_STATUS_STATE(status) (((status) >> 6) & 0x03)
 171 #define KCS_IDLE_STATE  0
 172 #define KCS_READ_STATE  1
 173 #define KCS_WRITE_STATE 2
 174 #define KCS_ERROR_STATE 3
 175 #define GET_STATUS_ATN(status) ((status) & 0x04)
 176 #define GET_STATUS_IBF(status) ((status) & 0x02)
 177 #define GET_STATUS_OBF(status) ((status) & 0x01)
 178
 179
 180 static inline void write_next_byte(struct si_sm_data *kcs)
 181 {
 182         write_data(kcs, kcs->write_data[kcs->write_pos]);
 183         (kcs->write_pos)++;
 184         (kcs->write_count)--;
 185 }
 186
 187 static inline void start_error_recovery(struct si_sm_data *kcs, char *reason)
 188 {
 189         (kcs->error_retries)++;
 190         if (kcs->error_retries > MAX_ERROR_RETRIES) {
 191                 if (kcs_debug & KCS_DEBUG_ENABLE)
 192                         dev_dbg(kcs->io->dev, "ipmi_kcs_sm: kcs hosed: %s\n",
 193                                 reason);
 194                 kcs->state = KCS_HOSED;
 195         } else {
 196                 kcs->error0_timeout = jiffies + ERROR0_OBF_WAIT_JIFFIES;
 197                 kcs->state = KCS_ERROR0;
 198         }
 199 }
 200
 201 static inline void read_next_byte(struct si_sm_data *kcs)
 202 {
 203         if (kcs->read_pos >= MAX_KCS_READ_SIZE) {
 204                 /* Throw the data away and mark it truncated. */
 205                 read_data(kcs);
 206                 kcs->truncated = 1;
 207         } else {
 208                 kcs->read_data[kcs->read_pos] = read_data(kcs);
 209                 (kcs->read_pos)++;
 210         }
 211         write_data(kcs, KCS_READ_BYTE);
 212 }
 213
 214 static inline int check_ibf(struct si_sm_data *kcs, unsigned char status,
 215                             long time)
 216 {
 217         if (GET_STATUS_IBF(status)) {
 218                 kcs->ibf_timeout -= time;
 219                 if (kcs->ibf_timeout < 0) {
 220                         start_error_recovery(kcs, "IBF not ready in time");
 221                         kcs->ibf_timeout = IBF_RETRY_TIMEOUT;
 222                         return 1;
 223                 }
 224                 return 0;
 225         }
 226         kcs->ibf_timeout = IBF_RETRY_TIMEOUT;
 227         return 1;
 228 }
 229
 230 static inline int check_obf(struct si_sm_data *kcs, unsigned char status,
 231                             long time)
 232 {
 233         if (!GET_STATUS_OBF(status)) {
 234                 kcs->obf_timeout -= time;
 235                 if (kcs->obf_timeout < 0) {
 236                         kcs->obf_timeout = OBF_RETRY_TIMEOUT;
 237                         start_error_recovery(kcs, "OBF not ready in time");
 238                         return 1;
 239                 }
 240                 return 0;
 241         }
 242         kcs->obf_timeout = OBF_RETRY_TIMEOUT;
 243         return 1;
 244 }
 245
 246 static void clear_obf(struct si_sm_data *kcs, unsigned char status)
 247 {
 248         if (GET_STATUS_OBF(status))
 249                 read_data(kcs);
 250 }
 251
 252 static void restart_kcs_transaction(struct si_sm_data *kcs)
 253 {
 254         kcs->write_count = kcs->orig_write_count;
 255         kcs->write_pos = 0;
 256         kcs->read_pos = 0;
 257         kcs->state = KCS_WAIT_WRITE_START;
 258         kcs->ibf_timeout = IBF_RETRY_TIMEOUT;
 259         kcs->obf_timeout = OBF_RETRY_TIMEOUT;
 260         write_cmd(kcs, KCS_WRITE_START);
 261 }
 262
 263 static int start_kcs_transaction(struct si_sm_data *kcs, unsigned char *data,
 264                                  unsigned int size)
 265 {
 266         unsigned int i;
 267
 268         if (size < 2)
 269                 return IPMI_REQ_LEN_INVALID_ERR;
 270         if (size > MAX_KCS_WRITE_SIZE)
 271                 return IPMI_REQ_LEN_EXCEEDED_ERR;
 272
 273         if ((kcs->state != KCS_IDLE) && (kcs->state != KCS_HOSED)) {
 274                 dev_warn(kcs->io->dev, "KCS in invalid state %d\n", kcs->state);
 275                 return IPMI_NOT_IN_MY_STATE_ERR;
 276         }
 277
 278         if (kcs_debug & KCS_DEBUG_MSG) {
 279                 dev_dbg(kcs->io->dev, "%s -", __func__);
 280                 for (i = 0; i < size; i++)
 281                         pr_cont(" %02x", data[i]);
 282                 pr_cont("\n");
 283         }
 284         kcs->error_retries = 0;
 285         memcpy(kcs->write_data, data, size);
 286         kcs->write_count = size;
 287         kcs->orig_write_count = size;
 288         kcs->write_pos = 0;
 289         kcs->read_pos = 0;
 290         kcs->state = KCS_START_OP;
 291         kcs->ibf_timeout = IBF_RETRY_TIMEOUT;
 292         kcs->obf_timeout = OBF_RETRY_TIMEOUT;
 293         return 0;
 294 }
 295
 296 static int get_kcs_result(struct si_sm_data *kcs, unsigned char *data,
 297                           unsigned int length)
 298 {
 299         if (length < kcs->read_pos) {
 300                 kcs->read_pos = length;
 301                 kcs->truncated = 1;
 302         }
 303
 304         memcpy(data, kcs->read_data, kcs->read_pos);
 305
 306         if ((length >= 3) && (kcs->read_pos < 3)) {
 307                 /* Guarantee that we return at least 3 bytes, with an
 308                    error in the third byte if it is too short. */
 309                 data[2] = IPMI_ERR_UNSPECIFIED;
 310                 kcs->read_pos = 3;
 311         }
 312         if (kcs->truncated) {
 313                 /*
 314                  * Report a truncated error.  We might overwrite
 315                  * another error, but that's too bad, the user needs
 316                  * to know it was truncated.
 317                  */
 318                 data[2] = IPMI_ERR_MSG_TRUNCATED;
 319                 kcs->truncated = 0;
 320         }
 321
 322         return kcs->read_pos;
 323 }
 324
 325 /*
 326  * This implements the state machine defined in the IPMI manual, see
 327  * that for details on how this works.  Divide that flowchart into
 328  * sections delimited by "Wait for IBF" and this will become clear.
 329  */
 330 static enum si_sm_result kcs_event(struct si_sm_data *kcs, long time)
 331 {
 332         unsigned char status;
 333         unsigned char state;
 334
 335         status = read_status(kcs);
 336
 337         if (kcs_debug & KCS_DEBUG_STATES)
 338                 dev_dbg(kcs->io->dev,
 339                         "KCS: State = %d, %x\n", kcs->state, status);
 340
 341         /* All states wait for ibf, so just do it here. */
 342         if (!check_ibf(kcs, status, time))
 343                 return SI_SM_CALL_WITH_DELAY;
 344
 345         /* Just about everything looks at the KCS state, so grab that, too. */
 346         state = GET_STATUS_STATE(status);
 347
 348         switch (kcs->state) {
 349         case KCS_IDLE:
 350                 /* If there's and interrupt source, turn it off. */
 351                 clear_obf(kcs, status);
 352
 353                 if (GET_STATUS_ATN(status))
 354                         return SI_SM_ATTN;
 355                 else
 356                         return SI_SM_IDLE;
 357
 358         case KCS_START_OP:
 359                 if (state != KCS_IDLE_STATE) {
 360                         start_error_recovery(kcs,
 361                                              "State machine not idle at start");
 362                         break;
 363                 }
 364
 365                 clear_obf(kcs, status);
 366                 write_cmd(kcs, KCS_WRITE_START);
 367                 kcs->state = KCS_WAIT_WRITE_START;
 368                 break;
 369
 370         case KCS_WAIT_WRITE_START:
 371                 if (state != KCS_WRITE_STATE) {
 372                         start_error_recovery(
 373                                 kcs,
 374                                 "Not in write state at write start");
 375                         break;
 376                 }
 377                 read_data(kcs);
 378                 if (kcs->write_count == 1) {
 379                         write_cmd(kcs, KCS_WRITE_END);
 380                         kcs->state = KCS_WAIT_WRITE_END;
 381                 } else {
 382                         write_next_byte(kcs);
 383                         kcs->state = KCS_WAIT_WRITE;
 384                 }
 385                 break;
 386
 387         case KCS_WAIT_WRITE:
 388                 if (state != KCS_WRITE_STATE) {
 389                         start_error_recovery(kcs,
 390                                              "Not in write state for write");
 391                         break;
 392                 }
 393                 clear_obf(kcs, status);
 394                 if (kcs->write_count == 1) {
 395                         write_cmd(kcs, KCS_WRITE_END);
 396                         kcs->state = KCS_WAIT_WRITE_END;
 397                 } else {
 398                         write_next_byte(kcs);
 399                 }
 400                 break;
 401
 402         case KCS_WAIT_WRITE_END:
 403                 if (state != KCS_WRITE_STATE) {
 404                         start_error_recovery(kcs,
 405                                              "Not in write state"
 406                                              " for write end");
 407                         break;
 408                 }
 409                 clear_obf(kcs, status);
 410                 write_next_byte(kcs);
 411                 kcs->state = KCS_WAIT_READ;
 412                 break;
 413
 414         case KCS_WAIT_READ:
 415                 if ((state != KCS_READ_STATE) && (state != KCS_IDLE_STATE)) {
 416                         start_error_recovery(
 417                                 kcs,
 418                                 "Not in read or idle in read state");
 419                         break;
 420                 }
 421
 422                 if (state == KCS_READ_STATE) {
 423                         if (!check_obf(kcs, status, time))
 424                                 return SI_SM_CALL_WITH_DELAY;
 425                         read_next_byte(kcs);
 426                 } else {
 427                         /*
 428                          * We don't implement this exactly like the state
 429                          * machine in the spec.  Some broken hardware
 430                          * does not write the final dummy byte to the
 431                          * read register.  Thus obf will never go high
 432                          * here.  We just go straight to idle, and we
 433                          * handle clearing out obf in idle state if it
 434                          * happens to come in.
 435                          */
 436                         clear_obf(kcs, status);
 437                         kcs->orig_write_count = 0;
 438                         kcs->state = KCS_IDLE;
 439                         return SI_SM_TRANSACTION_COMPLETE;
 440                 }
 441                 break;
 442
 443         case KCS_ERROR0:
 444                 clear_obf(kcs, status);
 445                 status = read_status(kcs);
 446                 if (GET_STATUS_OBF(status))
 447                         /* controller isn't responding */
 448                         if (time_before(jiffies, kcs->error0_timeout))
 449                                 return SI_SM_CALL_WITH_TICK_DELAY;
 450                 write_cmd(kcs, KCS_GET_STATUS_ABORT);
 451                 kcs->state = KCS_ERROR1;
 452                 break;
 453
 454         case KCS_ERROR1:
 455                 clear_obf(kcs, status);
 456                 write_data(kcs, 0);
 457                 kcs->state = KCS_ERROR2;
 458                 break;
 459
 460         case KCS_ERROR2:
 461                 if (state != KCS_READ_STATE) {
 462                         start_error_recovery(kcs,
 463                                              "Not in read state for error2");
 464                         break;
 465                 }
 466                 if (!check_obf(kcs, status, time))
 467                         return SI_SM_CALL_WITH_DELAY;
 468
 469                 clear_obf(kcs, status);
 470                 write_data(kcs, KCS_READ_BYTE);
 471                 kcs->state = KCS_ERROR3;
 472                 break;
 473
 474         case KCS_ERROR3:
 475                 if (state != KCS_IDLE_STATE) {
 476                         start_error_recovery(kcs,
 477                                              "Not in idle state for error3");
 478                         break;
 479                 }
 480
 481                 if (!check_obf(kcs, status, time))
 482                         return SI_SM_CALL_WITH_DELAY;
 483
 484                 clear_obf(kcs, status);
 485                 if (kcs->orig_write_count) {
 486                         restart_kcs_transaction(kcs);
 487                 } else {
 488                         kcs->state = KCS_IDLE;
 489                         return SI_SM_TRANSACTION_COMPLETE;
 490                 }
 491                 break;
 492
 493         case KCS_HOSED:
 494                 break;
 495         }
 496
 497         if (kcs->state == KCS_HOSED) {
 498                 init_kcs_data(kcs, kcs->io);
 499                 return SI_SM_HOSED;
 500         }
 501
 502         return SI_SM_CALL_WITHOUT_DELAY;
 503 }
 504
 505 static int kcs_size(void)
 506 {
 507         return sizeof(struct si_sm_data);
 508 }
 509
 510 static int kcs_detect(struct si_sm_data *kcs)
 511 {
 512         /*
 513          * It's impossible for the KCS status register to be all 1's,
 514          * (assuming a properly functioning, self-initialized BMC)
 515          * but that's what you get from reading a bogus address, so we
 516          * test that first.
 517          */
 518         if (read_status(kcs) == 0xff)
 519                 return 1;
 520
 521         return 0;
 522 }
 523
 524 static void kcs_cleanup(struct si_sm_data *kcs)
 525 {
 526 }
 527
 528 const struct si_sm_handlers kcs_smi_handlers = {
 529         .init_data         = init_kcs_data,
 530         .start_transaction = start_kcs_transaction,
 531         .get_result        = get_kcs_result,
 532         .event             = kcs_event,
 533         .detect            = kcs_detect,
 534         .cleanup           = kcs_cleanup,
 535         .size              = kcs_size,
 536 };