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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 | /* * Copyright (c) 2011-2015 Wind River Systems, Inc. * * SPDX-License-Identifier: Apache-2.0 */ /** * @file * @brief Intel Local APIC timer driver * * This module implements a kernel device driver for the Intel local APIC * timer device. It provides the standard "system clock driver" interfaces for * use with P6 (PentiumPro, II, III) and P7 (Pentium4) family processors. * The local APIC timer contains a 32-bit programmable down counter that * generates an interrupt for use by the local processor when it reaches zero. * The time base is derived from the processor's bus clock, divided by a value * specified in the divide configuration register. After reset, the timer is * initialized to zero. * * Typically, the local APIC timer operates in periodic mode. That is, after * its down counter reaches zero and triggers a timer interrupt, it is reset * to its initial value and the down counting continues. * * If the TICKLESS_IDLE kernel configuration option is enabled, the timer may * be programmed to wake the system in N >= TICKLESS_IDLE_THRESH ticks. The * kernel invokes _timer_idle_enter() to program the down counter in one-shot * mode to trigger an interrupt in N ticks. When the timer expires or when * another interrupt is detected, the kernel's interrupt stub invokes * _timer_idle_exit() to leave the tickless idle state. * * @internal * Factors that increase the driver's complexity: * * 1. As the down-counter is a 32-bit value, the number of ticks for which the * system can be in tickless idle is limited to 'max_system_ticks'; This * corresponds to 'cycles_per_max_ticks' (as the timer is programmed in cycles). * * 2. When the request to enter tickless arrives, any remaining cycles until * the next tick must be accounted for to maintain accuracy. * * 3. The act of entering tickless idle may potentially straddle a tick * boundary. Thus the number of remaining cycles to the next tick read from * the down counter is suspect as it could occur before or after the tick * boundary (thus before or after the counter is reset). If the tick is * straddled, the following will occur: * a. Enter tickless idle in one-shot mode * b. Immediately leave tickless idle * c. Process the tick event in the _timer_int_handler() and revert * to periodic mode. * d. Re-run the scheduler and possibly re-enter tickless idle * * 4. Tickless idle may be prematurely aborted due to a straddled tick. See * previous factor. * * 5. Tickless idle may be prematurely aborted due to a non-timer interrupt. * Its handler may make a task or fiber ready to run, so any elapsed ticks * must be accounted for and the timer must also expire at the end of the * next logical tick so _timer_int_handler() can put it back in periodic mode. * This can only be distinguished from the previous factor by the executiion of * _timer_int_handler(). * * 6. Tickless idle may end naturally. The down counter should be zero in * this case. However, some targets do not implement the local APIC timer * correctly and the down-counter continues to decrement. * @endinternal */ #include <kernel.h> #include <toolchain.h> #include <sections.h> #include <sys_clock.h> #include <drivers/system_timer.h> #include <arch/x86/irq_controller.h> #include <power.h> #include <device.h> #include <board.h> /* Local APIC Timer Bits */ #define LOAPIC_TIMER_DIVBY_2 0x0 /* Divide by 2 */ #define LOAPIC_TIMER_DIVBY_4 0x1 /* Divide by 4 */ #define LOAPIC_TIMER_DIVBY_8 0x2 /* Divide by 8 */ #define LOAPIC_TIMER_DIVBY_16 0x3 /* Divide by 16 */ #define LOAPIC_TIMER_DIVBY_32 0x8 /* Divide by 32 */ #define LOAPIC_TIMER_DIVBY_64 0x9 /* Divide by 64 */ #define LOAPIC_TIMER_DIVBY_128 0xa /* Divide by 128 */ #define LOAPIC_TIMER_DIVBY_1 0xb /* Divide by 1 */ #define LOAPIC_TIMER_DIVBY_MASK 0xf /* mask bits */ #define LOAPIC_TIMER_PERIODIC 0x00020000 /* Timer Mode: Periodic */ /* Helpful macros and inlines for programming timer. * We support both standard LOAPIC, and MVIC which has a similar * interface */ #if defined(CONFIG_LOAPIC) #define _REG_TIMER ((volatile uint32_t *) \ (CONFIG_LOAPIC_BASE_ADDRESS + LOAPIC_TIMER)) #define _REG_TIMER_ICR ((volatile uint32_t *) \ (CONFIG_LOAPIC_BASE_ADDRESS + LOAPIC_TIMER_ICR)) #define _REG_TIMER_CCR ((volatile uint32_t *) \ (CONFIG_LOAPIC_BASE_ADDRESS + LOAPIC_TIMER_CCR)) #define _REG_TIMER_CFG ((volatile uint32_t *) \ (CONFIG_LOAPIC_BASE_ADDRESS + LOAPIC_TIMER_CONFIG)) #define TIMER_IRQ CONFIG_LOAPIC_TIMER_IRQ #define TIMER_IRQ_PRIORITY CONFIG_LOAPIC_TIMER_IRQ_PRIORITY #elif defined(CONFIG_MVIC) #define _REG_TIMER ((volatile uint32_t *)MVIC_LVTTIMER) #define _REG_TIMER_ICR ((volatile uint32_t *)MVIC_ICR) #define _REG_TIMER_CCR ((volatile uint32_t *)MVIC_CCR) /* MVIC has no TIMER_CFG register */ #define TIMER_IRQ CONFIG_MVIC_TIMER_IRQ #define TIMER_IRQ_PRIORITY -1 #endif #if defined(CONFIG_TICKLESS_IDLE) #define TIMER_MODE_ONE_SHOT 0 #define TIMER_MODE_PERIODIC 1 #else /* !CONFIG_TICKLESS_IDLE */ #define tickless_idle_init() \ do {/* nothing */ \ } while (0) #endif /* !CONFIG_TICKLESS_IDLE */ #if defined(CONFIG_TICKLESS_IDLE) extern int32_t _sys_idle_elapsed_ticks; #endif /* CONFIG_TICKLESS_IDLE */ /* computed counter 0 initial count value */ static uint32_t __noinit cycles_per_tick; #if defined(CONFIG_TICKLESS_IDLE) static uint32_t programmed_cycles; static uint32_t programmed_full_ticks; static uint32_t __noinit max_system_ticks; static uint32_t __noinit cycles_per_max_ticks; static bool timer_known_to_have_expired; static unsigned char timer_mode = TIMER_MODE_PERIODIC; #endif /* CONFIG_TICKLESS_IDLE */ #ifdef CONFIG_DEVICE_POWER_MANAGEMENT static uint32_t loapic_timer_device_power_state; static uint32_t reg_timer_save; #ifndef CONFIG_MVIC static uint32_t reg_timer_cfg_save; #endif #endif /** * * @brief Set the timer for periodic mode * * This routine sets the timer for periodic mode. * * @return N/A */ static inline void periodic_mode_set(void) { *_REG_TIMER |= LOAPIC_TIMER_PERIODIC; } /** * * @brief Set the initial count register * * This routine sets value from which the timer will count down. * Note that setting the value to zero stops the timer. * * @param count Count from which timer is to count down * @return N/A */ static inline void initial_count_register_set(uint32_t count) { *_REG_TIMER_ICR = count; } #if defined(CONFIG_TICKLESS_IDLE) /** * * @brief Set the timer for one shot mode * * This routine sets the timer for one shot mode. * * @return N/A */ static inline void one_shot_mode_set(void) { *_REG_TIMER &= ~LOAPIC_TIMER_PERIODIC; } #endif /* CONFIG_TICKLESS_IDLE */ /** * * @brief Set the rate at which the timer is decremented * * This routine sets rate at which the timer is decremented to match the * external bus frequency. * This is not supported with MVIC, only real LOAPIC. * * @return N/A */ #ifndef CONFIG_MVIC static inline void divide_configuration_register_set(void) { *_REG_TIMER_CFG = (*_REG_TIMER_CFG & ~0xf) | LOAPIC_TIMER_DIVBY_1; } #endif /** * * @brief Get the value from the current count register * * This routine gets the value from the timer's current count register. This * value is the 'time' remaining to decrement before the timer triggers an * interrupt. * * @return N/A */ static inline uint32_t current_count_register_get(void) { return *_REG_TIMER_CCR; } #if defined(CONFIG_TICKLESS_IDLE) /** * * @brief Get the value from the initial count register * * This routine gets the value from the initial count register. * * @return N/A */ static inline uint32_t initial_count_register_get(void) { return *_REG_TIMER_ICR; } #endif /* CONFIG_TICKLESS_IDLE */ void _timer_int_handler(void *unused /* parameter is not used */ ) { ARG_UNUSED(unused); #ifdef CONFIG_TICKLESS_IDLE if (timer_mode == TIMER_MODE_ONE_SHOT) { if (!timer_known_to_have_expired) { uint32_t cycles; /* * The timer fired unexpectedly. This is due to one of two cases: * 1. Entering tickless idle straddled a tick. * 2. Leaving tickless idle straddled the final tick. * Due to the timer reprogramming in _timer_idle_exit(), case #2 * can be handled as a fall-through. * * NOTE: Although the cycle count is supposed to stop decrementing * once it hits zero in one-shot mode, not all targets implement * this properly (and continue to decrement). Thus, we have to * perform a second comparison to check for wrap-around. */ cycles = current_count_register_get(); if ((cycles > 0) && (cycles < programmed_cycles)) { /* Case 1 */ _sys_idle_elapsed_ticks = 0; } } /* Return the timer to periodic mode */ initial_count_register_set(cycles_per_tick - 1); periodic_mode_set(); timer_known_to_have_expired = false; timer_mode = TIMER_MODE_PERIODIC; } _sys_clock_final_tick_announce(); #else _sys_clock_tick_announce(); #endif /*CONFIG_TICKLESS_IDLE*/ } #if defined(CONFIG_TICKLESS_IDLE) /** * * @brief Initialize the tickless idle feature * * This routine initializes the tickless idle feature. Note that the maximum * number of ticks that can elapse during a "tickless idle" is limited by * <cycles_per_tick>. The larger the value (the lower the tick frequency), * the fewer elapsed ticks during a "tickless idle". Conversely, the smaller * the value (the higher the tick frequency), the more elapsed ticks during a * "tickless idle". * * @return N/A */ static void tickless_idle_init(void) { /* * Calculate the maximum number of system ticks less one. This * guarantees that an overflow will not occur when any remaining * cycles are added to <cycles_per_max_ticks> when calculating * <programmed_cycles>. */ max_system_ticks = (0xffffffff / cycles_per_tick) - 1; cycles_per_max_ticks = max_system_ticks * cycles_per_tick; } /** * * @brief Place system timer into idle state * * Re-program the timer to enter into the idle state for the given number of * ticks. It is placed into one shot mode where it will fire in the number of * ticks supplied or the maximum number of ticks that can be programmed into * hardware. A value of -1 means inifinite number of ticks. * * @return N/A */ void _timer_idle_enter(int32_t ticks /* system ticks */ ) { uint32_t cycles; /* * Although interrupts are disabled, the LOAPIC timer is still counting * down. Take a snapshot of current count register to get the number of * cycles remaining in the timer before it signals an interrupt and apply * that towards the one-shot calculation to maintain accuracy. * * NOTE: If entering tickless idle straddles a tick, 'programmed_cycles' * and 'programmmed_full_ticks' may be incorrect as we do not know which * side of the tick the snapshot occurred. This is not a problem as the * values will be corrected once the straddling is detected. */ cycles = current_count_register_get(); if ((ticks == K_FOREVER) || (ticks > max_system_ticks)) { /* * The number of cycles until the timer must fire next might not fit * in the 32-bit counter register. To work around this, program * the counter to fire in the maximum number of ticks (plus any * remaining cycles). */ programmed_full_ticks = max_system_ticks; programmed_cycles = cycles + cycles_per_max_ticks; } else { programmed_full_ticks = ticks - 1; programmed_cycles = cycles + (programmed_full_ticks * cycles_per_tick); } /* Set timer to one-shot mode */ initial_count_register_set(programmed_cycles); one_shot_mode_set(); timer_mode = TIMER_MODE_ONE_SHOT; } /** * * @brief Handling of tickless idle when interrupted * * The routine is responsible for taking the timer out of idle mode and * generating an interrupt at the next tick interval. * * Note that in this routine, _sys_idle_elapsed_ticks must be zero because the * ticker has done its work and consumed all the ticks. This has to be true * otherwise idle mode wouldn't have been entered in the first place. * * @return N/A */ void _timer_idle_exit(void) { uint32_t remaining_cycles; uint32_t remaining_full_ticks; /* * Interrupts are locked and idling has ceased. The cause of the cessation * is unknown. It may be due to one of three cases. * 1. The timer, which was previously placed into one-shot mode has * counted down to zero and signaled an interrupt. * 2. A non-timer interrupt occurred. Note that the LOAPIC timer will * still continue to decrement and may yet signal an interrupt. * 3. The LOAPIC timer signaled an interrupt while the timer was being * programmed for one-shot mode. * * NOTE: Although the cycle count is supposed to stop decrementing once it * hits zero in one-shot mode, not all targets implement this properly * (and continue to decrement). Thus a second comparison is required to * check for wrap-around. */ remaining_cycles = current_count_register_get(); if ((remaining_cycles == 0) || (remaining_cycles >= programmed_cycles)) { /* * The timer has expired. The handler _timer_int_handler() is * guaranteed to execute. Track the number of elapsed ticks. The * handler _timer_int_handler() will account for the final tick. */ _sys_idle_elapsed_ticks = programmed_full_ticks; /* * Announce elapsed ticks to the kernel. Note we are guaranteed * that the timer ISR will execute before the tick event is serviced. * (The timer ISR reprograms the timer for the next tick.) */ _sys_clock_tick_announce(); timer_known_to_have_expired = true; return; } timer_known_to_have_expired = false; /* * Either a non-timer interrupt occurred, or we straddled a tick when * entering tickless idle. It is impossible to determine which occurred * at this point. Regardless of the cause, ensure that the timer will * expire at the end of the next tick in case the ISR makes any tasks * and/or fibers ready to run. * * NOTE #1: In the case of a straddled tick, the '_sys_idle_elapsed_ticks' * calculation below may result in either 0 or 1. If 1, then this may * result in a harmless extra call to _sys_clock_tick_announce(). * * NOTE #2: In the case of a straddled tick, it is assumed that when the * timer is reprogrammed, it will be reprogrammed with a cycle count * sufficiently close to one tick that the timer will not expire before * _timer_int_handler() is executed. */ remaining_full_ticks = remaining_cycles / cycles_per_tick; _sys_idle_elapsed_ticks = programmed_full_ticks - remaining_full_ticks; if (_sys_idle_elapsed_ticks > 0) { _sys_clock_tick_announce(); } if (remaining_full_ticks > 0) { /* * Re-program the timer (still in one-shot mode) to fire at the end of * the tick, being careful to not program zero thus stopping the timer. */ programmed_cycles = 1 + ((remaining_cycles - 1) % cycles_per_tick); initial_count_register_set(programmed_cycles); } } #endif /* CONFIG_TICKLESS_IDLE */ /** * * @brief Initialize and enable the system clock * * This routine is used to program the timer to deliver interrupts at the * rate specified via the 'sys_clock_us_per_tick' global variable. * * @return 0 */ int _sys_clock_driver_init(struct device *device) { ARG_UNUSED(device); /* determine the timer counter value (in timer clock cycles/system tick) */ cycles_per_tick = sys_clock_hw_cycles_per_tick; tickless_idle_init(); #ifndef CONFIG_MVIC divide_configuration_register_set(); #endif initial_count_register_set(cycles_per_tick - 1); periodic_mode_set(); #ifdef CONFIG_DEVICE_POWER_MANAGEMENT loapic_timer_device_power_state = DEVICE_PM_ACTIVE_STATE; #endif IRQ_CONNECT(TIMER_IRQ, TIMER_IRQ_PRIORITY, _timer_int_handler, 0, 0); /* Everything has been configured. It is now safe to enable the * interrupt */ irq_enable(TIMER_IRQ); return 0; } #ifdef CONFIG_DEVICE_POWER_MANAGEMENT static int sys_clock_suspend(struct device *dev) { ARG_UNUSED(dev); reg_timer_save = *_REG_TIMER; #ifndef CONFIG_MVIC reg_timer_cfg_save = *_REG_TIMER_CFG; #endif loapic_timer_device_power_state = DEVICE_PM_SUSPEND_STATE; return 0; } static int sys_clock_resume(struct device *dev) { ARG_UNUSED(dev); *_REG_TIMER = reg_timer_save; #ifndef CONFIG_MVIC *_REG_TIMER_CFG = reg_timer_cfg_save; #endif /* * It is difficult to accurately know the time spent in DS. * We can use TSC or RTC but that will create a dependency * on those components. Other issue is about what to do * with pending timers. Following are some options :- * * 1) Expire all timers based on time spent found using some * source like TSC * 2) Expire all timers anyway * 3) Expire only the timer at the top * 4) Contine from where the timer left * * 1 and 2 require change to how timers are handled. 4 may not * give a good user experience. After waiting for a long period * in DS, the system would appear dead if it waits again. * * Current implementation uses option 3. The top most timer is * expired. Following code will set the counter to a low number * so it would immediately expire and generate timer interrupt * which will process the top most timer. Note that timer IC * cannot be set to 0. Setting it to 0 will stop the timer. */ initial_count_register_set(1); loapic_timer_device_power_state = DEVICE_PM_ACTIVE_STATE; return 0; } /* * Implements the driver control management functionality * the *context may include IN data or/and OUT data */ int sys_clock_device_ctrl(struct device *port, uint32_t ctrl_command, void *context) { if (ctrl_command == DEVICE_PM_SET_POWER_STATE) { if (*((uint32_t *)context) == DEVICE_PM_SUSPEND_STATE) { return sys_clock_suspend(port); } else if (*((uint32_t *)context) == DEVICE_PM_ACTIVE_STATE) { return sys_clock_resume(port); } } else if (ctrl_command == DEVICE_PM_GET_POWER_STATE) { *((uint32_t *)context) = loapic_timer_device_power_state; return 0; } return 0; } #endif /** * * @brief Read the platform's timer hardware * * This routine returns the current time in terms of timer hardware clock * cycles. We use the x86 TSC as the LOAPIC timer can't be used as a periodic * system clock and a timestamp source at the same time. * * @return up counter of elapsed clock cycles */ uint32_t _timer_cycle_get_32(void) { #if CONFIG_TSC_CYCLES_PER_SEC != 0 uint64_t tsc; /* 64-bit math to avoid overflows */ tsc = _tsc_read() * (uint64_t)sys_clock_hw_cycles_per_sec / (uint64_t) CONFIG_TSC_CYCLES_PER_SEC; return (uint32_t)tsc; #else /* TSC runs same as the bus speed, nothing to do but return the TSC * value */ return _do_read_cpu_timestamp32(); #endif } #if defined(CONFIG_SYSTEM_CLOCK_DISABLE) /** * * @brief Stop announcing ticks into the kernel * * This routine simply disables the LOAPIC counter such that interrupts are no * longer delivered. * * @return N/A */ void sys_clock_disable(void) { unsigned int key; /* interrupt lock level */ key = irq_lock(); irq_disable(TIMER_IRQ); initial_count_register_set(0); irq_unlock(key); } #endif /* CONFIG_SYSTEM_CLOCK_DISABLE */ |