1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * drivers/clocksource/arm_global_timer.c 4 * 5 * Copyright (C) 2013 STMicroelectronics (R&D) Limited. 6 * Author: Stuart Menefy <stuart.menefy@st.com> 7 * Author: Srinivas Kandagatla <srinivas.kandagatla@st.com> 8 */ 9 10 #include <linux/init.h> 11 #include <linux/interrupt.h> 12 #include <linux/bitfield.h> 13 #include <linux/clocksource.h> 14 #include <linux/clockchips.h> 15 #include <linux/cpu.h> 16 #include <linux/clk.h> 17 #include <linux/delay.h> 18 #include <linux/err.h> 19 #include <linux/io.h> 20 #include <linux/of.h> 21 #include <linux/of_irq.h> 22 #include <linux/of_address.h> 23 #include <linux/sched_clock.h> 24 25 #include <asm/cputype.h> 26 27 #define GT_COUNTER0 0x00 28 #define GT_COUNTER1 0x04 29 30 #define GT_CONTROL 0x08 31 #define GT_CONTROL_TIMER_ENABLE BIT(0) /* this bit is NOT banked */ 32 #define GT_CONTROL_COMP_ENABLE BIT(1) /* banked */ 33 #define GT_CONTROL_IRQ_ENABLE BIT(2) /* banked */ 34 #define GT_CONTROL_AUTO_INC BIT(3) /* banked */ 35 #define GT_CONTROL_PRESCALER_MASK GENMASK(15, 8) 36 37 #define GT_INT_STATUS 0x0c 38 #define GT_INT_STATUS_EVENT_FLAG BIT(0) 39 40 #define GT_COMP0 0x10 41 #define GT_COMP1 0x14 42 #define GT_AUTO_INC 0x18 43 44 #define MAX_F_ERR 50 45 /* 46 * We are expecting to be clocked by the ARM peripheral clock. 47 * 48 * Note: it is assumed we are using a prescaler value of zero, so this is 49 * the units for all operations. 50 */ 51 static void __iomem *gt_base; 52 static struct notifier_block gt_clk_rate_change_nb; 53 static u32 gt_psv_new, gt_psv_bck; 54 static unsigned long gt_target_rate; 55 static int gt_ppi; 56 static struct clock_event_device __percpu *gt_evt; 57 58 /* 59 * To get the value from the Global Timer Counter register proceed as follows: 60 * 1. Read the upper 32-bit timer counter register 61 * 2. Read the lower 32-bit timer counter register 62 * 3. Read the upper 32-bit timer counter register again. If the value is 63 * different to the 32-bit upper value read previously, go back to step 2. 64 * Otherwise the 64-bit timer counter value is correct. 65 */ 66 static u64 notrace _gt_counter_read(void) 67 { 68 u64 counter; 69 u32 lower; 70 u32 upper, old_upper; 71 72 upper = readl_relaxed(gt_base + GT_COUNTER1); 73 do { 74 old_upper = upper; 75 lower = readl_relaxed(gt_base + GT_COUNTER0); 76 upper = readl_relaxed(gt_base + GT_COUNTER1); 77 } while (upper != old_upper); 78 79 counter = upper; 80 counter <<= 32; 81 counter |= lower; 82 return counter; 83 } 84 85 static u64 gt_counter_read(void) 86 { 87 return _gt_counter_read(); 88 } 89 90 /* 91 * To ensure that updates to comparator value register do not set the 92 * Interrupt Status Register proceed as follows: 93 * 1. Clear the Comp Enable bit in the Timer Control Register. 94 * 2. Write the lower 32-bit Comparator Value Register. 95 * 3. Write the upper 32-bit Comparator Value Register. 96 * 4. Set the Comp Enable bit and, if necessary, the IRQ enable bit. 97 */ 98 static void gt_compare_set(unsigned long delta, int periodic) 99 { 100 u64 counter = gt_counter_read(); 101 unsigned long ctrl; 102 103 counter += delta; 104 ctrl = readl(gt_base + GT_CONTROL); 105 ctrl &= ~(GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE | 106 GT_CONTROL_AUTO_INC); 107 ctrl |= GT_CONTROL_TIMER_ENABLE; 108 writel_relaxed(ctrl, gt_base + GT_CONTROL); 109 writel_relaxed(lower_32_bits(counter), gt_base + GT_COMP0); 110 writel_relaxed(upper_32_bits(counter), gt_base + GT_COMP1); 111 112 if (periodic) { 113 writel_relaxed(delta, gt_base + GT_AUTO_INC); 114 ctrl |= GT_CONTROL_AUTO_INC; 115 } 116 117 ctrl |= GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE; 118 writel_relaxed(ctrl, gt_base + GT_CONTROL); 119 } 120 121 static int gt_clockevent_shutdown(struct clock_event_device *evt) 122 { 123 unsigned long ctrl; 124 125 ctrl = readl(gt_base + GT_CONTROL); 126 ctrl &= ~(GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE | 127 GT_CONTROL_AUTO_INC); 128 writel(ctrl, gt_base + GT_CONTROL); 129 return 0; 130 } 131 132 static int gt_clockevent_set_periodic(struct clock_event_device *evt) 133 { 134 gt_compare_set(DIV_ROUND_CLOSEST(gt_target_rate, HZ), 1); 135 return 0; 136 } 137 138 static int gt_clockevent_set_next_event(unsigned long evt, 139 struct clock_event_device *unused) 140 { 141 gt_compare_set(evt, 0); 142 return 0; 143 } 144 145 static irqreturn_t gt_clockevent_interrupt(int irq, void *dev_id) 146 { 147 struct clock_event_device *evt = dev_id; 148 149 if (!(readl_relaxed(gt_base + GT_INT_STATUS) & 150 GT_INT_STATUS_EVENT_FLAG)) 151 return IRQ_NONE; 152 153 /** 154 * ERRATA 740657( Global Timer can send 2 interrupts for 155 * the same event in single-shot mode) 156 * Workaround: 157 * Either disable single-shot mode. 158 * Or 159 * Modify the Interrupt Handler to avoid the 160 * offending sequence. This is achieved by clearing 161 * the Global Timer flag _after_ having incremented 162 * the Comparator register value to a higher value. 163 */ 164 if (clockevent_state_oneshot(evt)) 165 gt_compare_set(ULONG_MAX, 0); 166 167 writel_relaxed(GT_INT_STATUS_EVENT_FLAG, gt_base + GT_INT_STATUS); 168 evt->event_handler(evt); 169 170 return IRQ_HANDLED; 171 } 172 173 static int gt_starting_cpu(unsigned int cpu) 174 { 175 struct clock_event_device *clk = this_cpu_ptr(gt_evt); 176 177 clk->name = "arm_global_timer"; 178 clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT | 179 CLOCK_EVT_FEAT_PERCPU; 180 clk->set_state_shutdown = gt_clockevent_shutdown; 181 clk->set_state_periodic = gt_clockevent_set_periodic; 182 clk->set_state_oneshot = gt_clockevent_shutdown; 183 clk->set_state_oneshot_stopped = gt_clockevent_shutdown; 184 clk->set_next_event = gt_clockevent_set_next_event; 185 clk->cpumask = cpumask_of(cpu); 186 clk->rating = 300; 187 clk->irq = gt_ppi; 188 clockevents_config_and_register(clk, gt_target_rate, 189 1, 0xffffffff); 190 enable_percpu_irq(clk->irq, IRQ_TYPE_NONE); 191 return 0; 192 } 193 194 static int gt_dying_cpu(unsigned int cpu) 195 { 196 struct clock_event_device *clk = this_cpu_ptr(gt_evt); 197 198 disable_percpu_irq(clk->irq); 199 return 0; 200 } 201 202 static u64 gt_clocksource_read(struct clocksource *cs) 203 { 204 return gt_counter_read(); 205 } 206 207 static void gt_resume(struct clocksource *cs) 208 { 209 unsigned long ctrl; 210 211 ctrl = readl(gt_base + GT_CONTROL); 212 if (!(ctrl & GT_CONTROL_TIMER_ENABLE)) 213 /* re-enable timer on resume */ 214 writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL); 215 } 216 217 static struct clocksource gt_clocksource = { 218 .name = "arm_global_timer", 219 .rating = 300, 220 .read = gt_clocksource_read, 221 .mask = CLOCKSOURCE_MASK(64), 222 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 223 .resume = gt_resume, 224 }; 225 226 #ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK 227 static u64 notrace gt_sched_clock_read(void) 228 { 229 return _gt_counter_read(); 230 } 231 #endif 232 233 static unsigned long gt_read_long(void) 234 { 235 return readl_relaxed(gt_base + GT_COUNTER0); 236 } 237 238 static struct delay_timer gt_delay_timer = { 239 .read_current_timer = gt_read_long, 240 }; 241 242 static void gt_write_presc(u32 psv) 243 { 244 u32 reg; 245 246 reg = readl(gt_base + GT_CONTROL); 247 reg &= ~GT_CONTROL_PRESCALER_MASK; 248 reg |= FIELD_PREP(GT_CONTROL_PRESCALER_MASK, psv); 249 writel(reg, gt_base + GT_CONTROL); 250 } 251 252 static u32 gt_read_presc(void) 253 { 254 u32 reg; 255 256 reg = readl(gt_base + GT_CONTROL); 257 return FIELD_GET(GT_CONTROL_PRESCALER_MASK, reg); 258 } 259 260 static void __init gt_delay_timer_init(void) 261 { 262 gt_delay_timer.freq = gt_target_rate; 263 register_current_timer_delay(>_delay_timer); 264 } 265 266 static int __init gt_clocksource_init(unsigned int psv) 267 { 268 writel(0, gt_base + GT_CONTROL); 269 writel(0, gt_base + GT_COUNTER0); 270 writel(0, gt_base + GT_COUNTER1); 271 /* set prescaler and enable timer on all the cores */ 272 writel(FIELD_PREP(GT_CONTROL_PRESCALER_MASK, psv - 1) | 273 GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL); 274 275 #ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK 276 sched_clock_register(gt_sched_clock_read, 64, gt_target_rate); 277 #endif 278 return clocksource_register_hz(>_clocksource, gt_target_rate); 279 } 280 281 static int gt_clk_rate_change_cb(struct notifier_block *nb, 282 unsigned long event, void *data) 283 { 284 struct clk_notifier_data *ndata = data; 285 286 switch (event) { 287 case PRE_RATE_CHANGE: 288 { 289 unsigned long psv; 290 291 psv = DIV_ROUND_CLOSEST(ndata->new_rate, gt_target_rate); 292 if (!psv || 293 abs(gt_target_rate - (ndata->new_rate / psv)) > MAX_F_ERR) 294 return NOTIFY_BAD; 295 296 psv--; 297 298 /* prescaler within legal range? */ 299 if (!FIELD_FIT(GT_CONTROL_PRESCALER_MASK, psv)) 300 return NOTIFY_BAD; 301 302 /* 303 * store timer clock ctrl register so we can restore it in case 304 * of an abort. 305 */ 306 gt_psv_bck = gt_read_presc(); 307 gt_psv_new = psv; 308 /* scale down: adjust divider in post-change notification */ 309 if (ndata->new_rate < ndata->old_rate) 310 return NOTIFY_DONE; 311 312 /* scale up: adjust divider now - before frequency change */ 313 gt_write_presc(psv); 314 break; 315 } 316 case POST_RATE_CHANGE: 317 /* scale up: pre-change notification did the adjustment */ 318 if (ndata->new_rate > ndata->old_rate) 319 return NOTIFY_OK; 320 321 /* scale down: adjust divider now - after frequency change */ 322 gt_write_presc(gt_psv_new); 323 break; 324 325 case ABORT_RATE_CHANGE: 326 /* we have to undo the adjustment in case we scale up */ 327 if (ndata->new_rate < ndata->old_rate) 328 return NOTIFY_OK; 329 330 /* restore original register value */ 331 gt_write_presc(gt_psv_bck); 332 break; 333 default: 334 return NOTIFY_DONE; 335 } 336 337 return NOTIFY_DONE; 338 } 339 340 struct gt_prescaler_config { 341 const char *compatible; 342 unsigned long prescaler; 343 }; 344 345 static const struct gt_prescaler_config gt_prescaler_configs[] = { 346 /* 347 * On am43 the global timer clock is a child of the clock used for CPU 348 * OPPs, so the initial prescaler has to be compatible with all OPPs 349 * which are 300, 600, 720, 800 and 1000 with a fixed divider of 2, this 350 * gives us a GCD of 10. Initial frequency is 1000, so the prescaler is 351 * 50. 352 */ 353 { .compatible = "ti,am43", .prescaler = 50 }, 354 { .compatible = "xlnx,zynq-7000", .prescaler = 2 }, 355 { .compatible = NULL } 356 }; 357 358 static unsigned long gt_get_initial_prescaler_value(struct device_node *np) 359 { 360 const struct gt_prescaler_config *config; 361 362 if (CONFIG_ARM_GT_INITIAL_PRESCALER_VAL != 0) 363 return CONFIG_ARM_GT_INITIAL_PRESCALER_VAL; 364 365 for (config = gt_prescaler_configs; config->compatible; config++) { 366 if (of_machine_is_compatible(config->compatible)) 367 return config->prescaler; 368 } 369 370 return 1; 371 } 372 373 static int __init global_timer_of_register(struct device_node *np) 374 { 375 struct clk *gt_clk; 376 static unsigned long gt_clk_rate; 377 int err; 378 unsigned long psv; 379 380 /* 381 * In A9 r2p0 the comparators for each processor with the global timer 382 * fire when the timer value is greater than or equal to. In previous 383 * revisions the comparators fired when the timer value was equal to. 384 */ 385 if (read_cpuid_part() == ARM_CPU_PART_CORTEX_A9 386 && (read_cpuid_id() & 0xf0000f) < 0x200000) { 387 pr_warn("global-timer: non support for this cpu version.\n"); 388 return -ENOSYS; 389 } 390 391 gt_ppi = irq_of_parse_and_map(np, 0); 392 if (!gt_ppi) { 393 pr_warn("global-timer: unable to parse irq\n"); 394 return -EINVAL; 395 } 396 397 gt_base = of_iomap(np, 0); 398 if (!gt_base) { 399 pr_warn("global-timer: invalid base address\n"); 400 return -ENXIO; 401 } 402 403 gt_clk = of_clk_get(np, 0); 404 if (!IS_ERR(gt_clk)) { 405 err = clk_prepare_enable(gt_clk); 406 if (err) 407 goto out_unmap; 408 } else { 409 pr_warn("global-timer: clk not found\n"); 410 err = -EINVAL; 411 goto out_unmap; 412 } 413 414 psv = gt_get_initial_prescaler_value(np); 415 gt_clk_rate = clk_get_rate(gt_clk); 416 gt_target_rate = gt_clk_rate / psv; 417 gt_clk_rate_change_nb.notifier_call = 418 gt_clk_rate_change_cb; 419 err = clk_notifier_register(gt_clk, >_clk_rate_change_nb); 420 if (err) { 421 pr_warn("Unable to register clock notifier\n"); 422 goto out_clk; 423 } 424 425 gt_evt = alloc_percpu(struct clock_event_device); 426 if (!gt_evt) { 427 pr_warn("global-timer: can't allocate memory\n"); 428 err = -ENOMEM; 429 goto out_clk_nb; 430 } 431 432 err = request_percpu_irq(gt_ppi, gt_clockevent_interrupt, 433 "gt", gt_evt); 434 if (err) { 435 pr_warn("global-timer: can't register interrupt %d (%d)\n", 436 gt_ppi, err); 437 goto out_free; 438 } 439 440 /* Register and immediately configure the timer on the boot CPU */ 441 err = gt_clocksource_init(psv); 442 if (err) 443 goto out_irq; 444 445 err = cpuhp_setup_state(CPUHP_AP_ARM_GLOBAL_TIMER_STARTING, 446 "clockevents/arm/global_timer:starting", 447 gt_starting_cpu, gt_dying_cpu); 448 if (err) 449 goto out_irq; 450 451 gt_delay_timer_init(); 452 453 return 0; 454 455 out_irq: 456 free_percpu_irq(gt_ppi, gt_evt); 457 out_free: 458 free_percpu(gt_evt); 459 out_clk_nb: 460 clk_notifier_unregister(gt_clk, >_clk_rate_change_nb); 461 out_clk: 462 clk_disable_unprepare(gt_clk); 463 out_unmap: 464 iounmap(gt_base); 465 WARN(err, "ARM Global timer register failed (%d)\n", err); 466 467 return err; 468 } 469 470 /* Only tested on r2p2 and r3p0 */ 471 TIMER_OF_DECLARE(arm_gt, "arm,cortex-a9-global-timer", 472 global_timer_of_register); 473