drivers/clocksource/cadence_ttc_timer.c

   1 /*
   2  * This file contains driver for the Cadence Triple Timer Counter Rev 06
   3  *
   4  *  Copyright (C) 2011-2013 Xilinx
   5  *
   6  * based on arch/mips/kernel/time.c timer driver
   7  *
   8  * This software is licensed under the terms of the GNU General Public
   9  * License version 2, as published by the Free Software Foundation, and
  10  * may be copied, distributed, and modified under those terms.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  */
  17
  18 #include <linux/clk.h>
  19 #include <linux/clk-provider.h>
  20 #include <linux/interrupt.h>
  21 #include <linux/clockchips.h>
  22 #include <linux/of_address.h>
  23 #include <linux/of_irq.h>
  24 #include <linux/slab.h>
  25 #include <linux/sched_clock.h>
  26
  27 /*
  28  * This driver configures the 2 16-bit count-up timers as follows:
  29  *
  30  * T1: Timer 1, clocksource for generic timekeeping
  31  * T2: Timer 2, clockevent source for hrtimers
  32  * T3: Timer 3, <unused>
  33  *
  34  * The input frequency to the timer module for emulation is 2.5MHz which is
  35  * common to all the timer channels (T1, T2, and T3). With a pre-scaler of 32,
  36  * the timers are clocked at 78.125KHz (12.8 us resolution).
  37
  38  * The input frequency to the timer module in silicon is configurable and
  39  * obtained from device tree. The pre-scaler of 32 is used.
  40  */
  41
  42 /*
  43  * Timer Register Offset Definitions of Timer 1, Increment base address by 4
  44  * and use same offsets for Timer 2
  45  */
  46 #define TTC_CLK_CNTRL_OFFSET            0x00 /* Clock Control Reg, RW */
  47 #define TTC_CNT_CNTRL_OFFSET            0x0C /* Counter Control Reg, RW */
  48 #define TTC_COUNT_VAL_OFFSET            0x18 /* Counter Value Reg, RO */
  49 #define TTC_INTR_VAL_OFFSET             0x24 /* Interval Count Reg, RW */
  50 #define TTC_ISR_OFFSET          0x54 /* Interrupt Status Reg, RO */
  51 #define TTC_IER_OFFSET          0x60 /* Interrupt Enable Reg, RW */
  52
  53 #define TTC_CNT_CNTRL_DISABLE_MASK      0x1
  54
  55 #define TTC_CLK_CNTRL_CSRC_MASK         (1 << 5)        /* clock source */
  56 #define TTC_CLK_CNTRL_PSV_MASK          0x1e
  57 #define TTC_CLK_CNTRL_PSV_SHIFT         1
  58
  59 /*
  60  * Setup the timers to use pre-scaling, using a fixed value for now that will
  61  * work across most input frequency, but it may need to be more dynamic
  62  */
  63 #define PRESCALE_EXPONENT       11      /* 2 ^ PRESCALE_EXPONENT = PRESCALE */
  64 #define PRESCALE                2048    /* The exponent must match this */
  65 #define CLK_CNTRL_PRESCALE      ((PRESCALE_EXPONENT - 1) << 1)
  66 #define CLK_CNTRL_PRESCALE_EN   1
  67 #define CNT_CNTRL_RESET         (1 << 4)
  68
  69 #define MAX_F_ERR 50
  70
  71 /**
  72  * struct ttc_timer - This definition defines local timer structure
  73  *
  74  * @base_addr:  Base address of timer
  75  * @freq:       Timer input clock frequency
  76  * @clk:        Associated clock source
  77  * @clk_rate_change_nb  Notifier block for clock rate changes
  78  */
  79 struct ttc_timer {
  80         void __iomem *base_addr;
  81         unsigned long freq;
  82         struct clk *clk;
  83         struct notifier_block clk_rate_change_nb;
  84 };
  85
  86 #define to_ttc_timer(x) \
  87                 container_of(x, struct ttc_timer, clk_rate_change_nb)
  88
  89 struct ttc_timer_clocksource {
  90         u32                     scale_clk_ctrl_reg_old;
  91         u32                     scale_clk_ctrl_reg_new;
  92         struct ttc_timer        ttc;
  93         struct clocksource      cs;
  94 };
  95
  96 #define to_ttc_timer_clksrc(x) \
  97                 container_of(x, struct ttc_timer_clocksource, cs)
  98
  99 struct ttc_timer_clockevent {
 100         struct ttc_timer                ttc;
 101         struct clock_event_device       ce;
 102 };
 103
 104 #define to_ttc_timer_clkevent(x) \
 105                 container_of(x, struct ttc_timer_clockevent, ce)
 106
 107 static void __iomem *ttc_sched_clock_val_reg;
 108
 109 /**
 110  * ttc_set_interval - Set the timer interval value
 111  *
 112  * @timer:      Pointer to the timer instance
 113  * @cycles:     Timer interval ticks
 114  **/
 115 static void ttc_set_interval(struct ttc_timer *timer,
 116                                         unsigned long cycles)
 117 {
 118         u32 ctrl_reg;
 119
 120         /* Disable the counter, set the counter value  and re-enable counter */
 121         ctrl_reg = readl_relaxed(timer->base_addr + TTC_CNT_CNTRL_OFFSET);
 122         ctrl_reg |= TTC_CNT_CNTRL_DISABLE_MASK;
 123         writel_relaxed(ctrl_reg, timer->base_addr + TTC_CNT_CNTRL_OFFSET);
 124
 125         writel_relaxed(cycles, timer->base_addr + TTC_INTR_VAL_OFFSET);
 126
 127         /*
 128          * Reset the counter (0x10) so that it starts from 0, one-shot
 129          * mode makes this needed for timing to be right.
 130          */
 131         ctrl_reg |= CNT_CNTRL_RESET;
 132         ctrl_reg &= ~TTC_CNT_CNTRL_DISABLE_MASK;
 133         writel_relaxed(ctrl_reg, timer->base_addr + TTC_CNT_CNTRL_OFFSET);
 134 }
 135
 136 /**
 137  * ttc_clock_event_interrupt - Clock event timer interrupt handler
 138  *
 139  * @irq:        IRQ number of the Timer
 140  * @dev_id:     void pointer to the ttc_timer instance
 141  *
 142  * returns: Always IRQ_HANDLED - success
 143  **/
 144 static irqreturn_t ttc_clock_event_interrupt(int irq, void *dev_id)
 145 {
 146         struct ttc_timer_clockevent *ttce = dev_id;
 147         struct ttc_timer *timer = &ttce->ttc;
 148
 149         /* Acknowledge the interrupt and call event handler */
 150         readl_relaxed(timer->base_addr + TTC_ISR_OFFSET);
 151
 152         ttce->ce.event_handler(&ttce->ce);
 153
 154         return IRQ_HANDLED;
 155 }
 156
 157 /**
 158  * __ttc_clocksource_read - Reads the timer counter register
 159  *
 160  * returns: Current timer counter register value
 161  **/
 162 static cycle_t __ttc_clocksource_read(struct clocksource *cs)
 163 {
 164         struct ttc_timer *timer = &to_ttc_timer_clksrc(cs)->ttc;
 165
 166         return (cycle_t)readl_relaxed(timer->base_addr +
 167                                 TTC_COUNT_VAL_OFFSET);
 168 }
 169
 170 static u64 notrace ttc_sched_clock_read(void)
 171 {
 172         return readl_relaxed(ttc_sched_clock_val_reg);
 173 }
 174
 175 /**
 176  * ttc_set_next_event - Sets the time interval for next event
 177  *
 178  * @cycles:     Timer interval ticks
 179  * @evt:        Address of clock event instance
 180  *
 181  * returns: Always 0 - success
 182  **/
 183 static int ttc_set_next_event(unsigned long cycles,
 184                                         struct clock_event_device *evt)
 185 {
 186         struct ttc_timer_clockevent *ttce = to_ttc_timer_clkevent(evt);
 187         struct ttc_timer *timer = &ttce->ttc;
 188
 189         ttc_set_interval(timer, cycles);
 190         return 0;
 191 }
 192
 193 /**
 194  * ttc_set_mode - Sets the mode of timer
 195  *
 196  * @mode:       Mode to be set
 197  * @evt:        Address of clock event instance
 198  **/
 199 static void ttc_set_mode(enum clock_event_mode mode,
 200                                         struct clock_event_device *evt)
 201 {
 202         struct ttc_timer_clockevent *ttce = to_ttc_timer_clkevent(evt);
 203         struct ttc_timer *timer = &ttce->ttc;
 204         u32 ctrl_reg;
 205
 206         switch (mode) {
 207         case CLOCK_EVT_MODE_PERIODIC:
 208                 ttc_set_interval(timer, DIV_ROUND_CLOSEST(ttce->ttc.freq,
 209                                                 PRESCALE * HZ));
 210                 break;
 211         case CLOCK_EVT_MODE_ONESHOT:
 212         case CLOCK_EVT_MODE_UNUSED:
 213         case CLOCK_EVT_MODE_SHUTDOWN:
 214                 ctrl_reg = readl_relaxed(timer->base_addr +
 215                                         TTC_CNT_CNTRL_OFFSET);
 216                 ctrl_reg |= TTC_CNT_CNTRL_DISABLE_MASK;
 217                 writel_relaxed(ctrl_reg,
 218                                 timer->base_addr + TTC_CNT_CNTRL_OFFSET);
 219                 break;
 220         case CLOCK_EVT_MODE_RESUME:
 221                 ctrl_reg = readl_relaxed(timer->base_addr +
 222                                         TTC_CNT_CNTRL_OFFSET);
 223                 ctrl_reg &= ~TTC_CNT_CNTRL_DISABLE_MASK;
 224                 writel_relaxed(ctrl_reg,
 225                                 timer->base_addr + TTC_CNT_CNTRL_OFFSET);
 226                 break;
 227         }
 228 }
 229
 230 static int ttc_rate_change_clocksource_cb(struct notifier_block *nb,
 231                 unsigned long event, void *data)
 232 {
 233         struct clk_notifier_data *ndata = data;
 234         struct ttc_timer *ttc = to_ttc_timer(nb);
 235         struct ttc_timer_clocksource *ttccs = container_of(ttc,
 236                         struct ttc_timer_clocksource, ttc);
 237
 238         switch (event) {
 239         case PRE_RATE_CHANGE:
 240         {
 241                 u32 psv;
 242                 unsigned long factor, rate_low, rate_high;
 243
 244                 if (ndata->new_rate > ndata->old_rate) {
 245                         factor = DIV_ROUND_CLOSEST(ndata->new_rate,
 246                                         ndata->old_rate);
 247                         rate_low = ndata->old_rate;
 248                         rate_high = ndata->new_rate;
 249                 } else {
 250                         factor = DIV_ROUND_CLOSEST(ndata->old_rate,
 251                                         ndata->new_rate);
 252                         rate_low = ndata->new_rate;
 253                         rate_high = ndata->old_rate;
 254                 }
 255
 256                 if (!is_power_of_2(factor))
 257                                 return NOTIFY_BAD;
 258
 259                 if (abs(rate_high - (factor * rate_low)) > MAX_F_ERR)
 260                         return NOTIFY_BAD;
 261
 262                 factor = __ilog2_u32(factor);
 263
 264                 /*
 265                  * store timer clock ctrl register so we can restore it in case
 266                  * of an abort.
 267                  */
 268                 ttccs->scale_clk_ctrl_reg_old =
 269                         readl_relaxed(ttccs->ttc.base_addr +
 270                         TTC_CLK_CNTRL_OFFSET);
 271
 272                 psv = (ttccs->scale_clk_ctrl_reg_old &
 273                                 TTC_CLK_CNTRL_PSV_MASK) >>
 274                                 TTC_CLK_CNTRL_PSV_SHIFT;
 275                 if (ndata->new_rate < ndata->old_rate)
 276                         psv -= factor;
 277                 else
 278                         psv += factor;
 279
 280                 /* prescaler within legal range? */
 281                 if (psv & ~(TTC_CLK_CNTRL_PSV_MASK >> TTC_CLK_CNTRL_PSV_SHIFT))
 282                         return NOTIFY_BAD;
 283
 284                 ttccs->scale_clk_ctrl_reg_new = ttccs->scale_clk_ctrl_reg_old &
 285                         ~TTC_CLK_CNTRL_PSV_MASK;
 286                 ttccs->scale_clk_ctrl_reg_new |= psv << TTC_CLK_CNTRL_PSV_SHIFT;
 287
 288
 289                 /* scale down: adjust divider in post-change notification */
 290                 if (ndata->new_rate < ndata->old_rate)
 291                         return NOTIFY_DONE;
 292
 293                 /* scale up: adjust divider now - before frequency change */
 294                 writel_relaxed(ttccs->scale_clk_ctrl_reg_new,
 295                                ttccs->ttc.base_addr + TTC_CLK_CNTRL_OFFSET);
 296                 break;
 297         }
 298         case POST_RATE_CHANGE:
 299                 /* scale up: pre-change notification did the adjustment */
 300                 if (ndata->new_rate > ndata->old_rate)
 301                         return NOTIFY_OK;
 302
 303                 /* scale down: adjust divider now - after frequency change */
 304                 writel_relaxed(ttccs->scale_clk_ctrl_reg_new,
 305                                ttccs->ttc.base_addr + TTC_CLK_CNTRL_OFFSET);
 306                 break;
 307
 308         case ABORT_RATE_CHANGE:
 309                 /* we have to undo the adjustment in case we scale up */
 310                 if (ndata->new_rate < ndata->old_rate)
 311                         return NOTIFY_OK;
 312
 313                 /* restore original register value */
 314                 writel_relaxed(ttccs->scale_clk_ctrl_reg_old,
 315                                ttccs->ttc.base_addr + TTC_CLK_CNTRL_OFFSET);
 316                 /* fall through */
 317         default:
 318                 return NOTIFY_DONE;
 319         }
 320
 321         return NOTIFY_DONE;
 322 }
 323
 324 static void __init ttc_setup_clocksource(struct clk *clk, void __iomem *base)
 325 {
 326         struct ttc_timer_clocksource *ttccs;
 327         int err;
 328
 329         ttccs = kzalloc(sizeof(*ttccs), GFP_KERNEL);
 330         if (WARN_ON(!ttccs))
 331                 return;
 332
 333         ttccs->ttc.clk = clk;
 334
 335         err = clk_prepare_enable(ttccs->ttc.clk);
 336         if (WARN_ON(err)) {
 337                 kfree(ttccs);
 338                 return;
 339         }
 340
 341         ttccs->ttc.freq = clk_get_rate(ttccs->ttc.clk);
 342
 343         ttccs->ttc.clk_rate_change_nb.notifier_call =
 344                 ttc_rate_change_clocksource_cb;
 345         ttccs->ttc.clk_rate_change_nb.next = NULL;
 346         if (clk_notifier_register(ttccs->ttc.clk,
 347                                 &ttccs->ttc.clk_rate_change_nb))
 348                 pr_warn("Unable to register clock notifier.\n");
 349
 350         ttccs->ttc.base_addr = base;
 351         ttccs->cs.name = "ttc_clocksource";
 352         ttccs->cs.rating = 200;
 353         ttccs->cs.read = __ttc_clocksource_read;
 354         ttccs->cs.mask = CLOCKSOURCE_MASK(16);
 355         ttccs->cs.flags = CLOCK_SOURCE_IS_CONTINUOUS;
 356
 357         /*
 358          * Setup the clock source counter to be an incrementing counter
 359          * with no interrupt and it rolls over at 0xFFFF. Pre-scale
 360          * it by 32 also. Let it start running now.
 361          */
 362         writel_relaxed(0x0,  ttccs->ttc.base_addr + TTC_IER_OFFSET);
 363         writel_relaxed(CLK_CNTRL_PRESCALE | CLK_CNTRL_PRESCALE_EN,
 364                      ttccs->ttc.base_addr + TTC_CLK_CNTRL_OFFSET);
 365         writel_relaxed(CNT_CNTRL_RESET,
 366                      ttccs->ttc.base_addr + TTC_CNT_CNTRL_OFFSET);
 367
 368         err = clocksource_register_hz(&ttccs->cs, ttccs->ttc.freq / PRESCALE);
 369         if (WARN_ON(err)) {
 370                 kfree(ttccs);
 371                 return;
 372         }
 373
 374         ttc_sched_clock_val_reg = base + TTC_COUNT_VAL_OFFSET;
 375         sched_clock_register(ttc_sched_clock_read, 16, ttccs->ttc.freq / PRESCALE);
 376 }
 377
 378 static int ttc_rate_change_clockevent_cb(struct notifier_block *nb,
 379                 unsigned long event, void *data)
 380 {
 381         struct clk_notifier_data *ndata = data;
 382         struct ttc_timer *ttc = to_ttc_timer(nb);
 383         struct ttc_timer_clockevent *ttcce = container_of(ttc,
 384                         struct ttc_timer_clockevent, ttc);
 385
 386         switch (event) {
 387         case POST_RATE_CHANGE:
 388                 /* update cached frequency */
 389                 ttc->freq = ndata->new_rate;
 390
 391                 clockevents_update_freq(&ttcce->ce, ndata->new_rate / PRESCALE);
 392
 393                 /* fall through */
 394         case PRE_RATE_CHANGE:
 395         case ABORT_RATE_CHANGE:
 396         default:
 397                 return NOTIFY_DONE;
 398         }
 399 }
 400
 401 static void __init ttc_setup_clockevent(struct clk *clk,
 402                                                 void __iomem *base, u32 irq)
 403 {
 404         struct ttc_timer_clockevent *ttcce;
 405         int err;
 406
 407         ttcce = kzalloc(sizeof(*ttcce), GFP_KERNEL);
 408         if (WARN_ON(!ttcce))
 409                 return;
 410
 411         ttcce->ttc.clk = clk;
 412
 413         err = clk_prepare_enable(ttcce->ttc.clk);
 414         if (WARN_ON(err)) {
 415                 kfree(ttcce);
 416                 return;
 417         }
 418
 419         ttcce->ttc.clk_rate_change_nb.notifier_call =
 420                 ttc_rate_change_clockevent_cb;
 421         ttcce->ttc.clk_rate_change_nb.next = NULL;
 422         if (clk_notifier_register(ttcce->ttc.clk,
 423                                 &ttcce->ttc.clk_rate_change_nb))
 424                 pr_warn("Unable to register clock notifier.\n");
 425         ttcce->ttc.freq = clk_get_rate(ttcce->ttc.clk);
 426
 427         ttcce->ttc.base_addr = base;
 428         ttcce->ce.name = "ttc_clockevent";
 429         ttcce->ce.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
 430         ttcce->ce.set_next_event = ttc_set_next_event;
 431         ttcce->ce.set_mode = ttc_set_mode;
 432         ttcce->ce.rating = 200;
 433         ttcce->ce.irq = irq;
 434         ttcce->ce.cpumask = cpu_possible_mask;
 435
 436         /*
 437          * Setup the clock event timer to be an interval timer which
 438          * is prescaled by 32 using the interval interrupt. Leave it
 439          * disabled for now.
 440          */
 441         writel_relaxed(0x23, ttcce->ttc.base_addr + TTC_CNT_CNTRL_OFFSET);
 442         writel_relaxed(CLK_CNTRL_PRESCALE | CLK_CNTRL_PRESCALE_EN,
 443                      ttcce->ttc.base_addr + TTC_CLK_CNTRL_OFFSET);
 444         writel_relaxed(0x1,  ttcce->ttc.base_addr + TTC_IER_OFFSET);
 445
 446         err = request_irq(irq, ttc_clock_event_interrupt,
 447                           IRQF_TIMER, ttcce->ce.name, ttcce);
 448         if (WARN_ON(err)) {
 449                 kfree(ttcce);
 450                 return;
 451         }
 452
 453         clockevents_config_and_register(&ttcce->ce,
 454                         ttcce->ttc.freq / PRESCALE, 1, 0xfffe);
 455 }
 456
 457 /**
 458  * ttc_timer_init - Initialize the timer
 459  *
 460  * Initializes the timer hardware and register the clock source and clock event
 461  * timers with Linux kernal timer framework
 462  */
 463 static void __init ttc_timer_init(struct device_node *timer)
 464 {
 465         unsigned int irq;
 466         void __iomem *timer_baseaddr;
 467         struct clk *clk_cs, *clk_ce;
 468         static int initialized;
 469         int clksel;
 470
 471         if (initialized)
 472                 return;
 473
 474         initialized = 1;
 475
 476         /*
 477          * Get the 1st Triple Timer Counter (TTC) block from the device tree
 478          * and use it. Note that the event timer uses the interrupt and it's the
 479          * 2nd TTC hence the irq_of_parse_and_map(,1)
 480          */
 481         timer_baseaddr = of_iomap(timer, 0);
 482         if (!timer_baseaddr) {
 483                 pr_err("ERROR: invalid timer base address\n");
 484                 BUG();
 485         }
 486
 487         irq = irq_of_parse_and_map(timer, 1);
 488         if (irq <= 0) {
 489                 pr_err("ERROR: invalid interrupt number\n");
 490                 BUG();
 491         }
 492
 493         clksel = readl_relaxed(timer_baseaddr + TTC_CLK_CNTRL_OFFSET);
 494         clksel = !!(clksel & TTC_CLK_CNTRL_CSRC_MASK);
 495         clk_cs = of_clk_get(timer, clksel);
 496         if (IS_ERR(clk_cs)) {
 497                 pr_err("ERROR: timer input clock not found\n");
 498                 BUG();
 499         }
 500
 501         clksel = readl_relaxed(timer_baseaddr + 4 + TTC_CLK_CNTRL_OFFSET);
 502         clksel = !!(clksel & TTC_CLK_CNTRL_CSRC_MASK);
 503         clk_ce = of_clk_get(timer, clksel);
 504         if (IS_ERR(clk_ce)) {
 505                 pr_err("ERROR: timer input clock not found\n");
 506                 BUG();
 507         }
 508
 509         ttc_setup_clocksource(clk_cs, timer_baseaddr);
 510         ttc_setup_clockevent(clk_ce, timer_baseaddr + 4, irq);
 511
 512         pr_info("%s #0 at %p, irq=%d\n", timer->name, timer_baseaddr, irq);
 513 }
 514
 515 CLOCKSOURCE_OF_DECLARE(ttc, "cdns,ttc", ttc_timer_init);