drivers/clocksource/tcb_clksrc.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/init.h>
   3 #include <linux/clocksource.h>
   4 #include <linux/clockchips.h>
   5 #include <linux/interrupt.h>
   6 #include <linux/irq.h>
   7
   8 #include <linux/clk.h>
   9 #include <linux/err.h>
  10 #include <linux/ioport.h>
  11 #include <linux/io.h>
  12 #include <linux/platform_device.h>
  13 #include <linux/syscore_ops.h>
  14 #include <linux/atmel_tc.h>
  15
  16
  17 /*
  18  * We're configured to use a specific TC block, one that's not hooked
  19  * up to external hardware, to provide a time solution:
  20  *
  21  *   - Two channels combine to create a free-running 32 bit counter
  22  *     with a base rate of 5+ MHz, packaged as a clocksource (with
  23  *     resolution better than 200 nsec).
  24  *   - Some chips support 32 bit counter. A single channel is used for
  25  *     this 32 bit free-running counter. the second channel is not used.
  26  *
  27  *   - The third channel may be used to provide a 16-bit clockevent
  28  *     source, used in either periodic or oneshot mode.  This runs
  29  *     at 32 KiHZ, and can handle delays of up to two seconds.
  30  *
  31  * A boot clocksource and clockevent source are also currently needed,
  32  * unless the relevant platforms (ARM/AT91, AVR32/AT32) are changed so
  33  * this code can be used when init_timers() is called, well before most
  34  * devices are set up.  (Some low end AT91 parts, which can run uClinux,
  35  * have only the timers in one TC block... they currently don't support
  36  * the tclib code, because of that initialization issue.)
  37  *
  38  * REVISIT behavior during system suspend states... we should disable
  39  * all clocks and save the power.  Easily done for clockevent devices,
  40  * but clocksources won't necessarily get the needed notifications.
  41  * For deeper system sleep states, this will be mandatory...
  42  */
  43
  44 static void __iomem *tcaddr;
  45 static struct
  46 {
  47         u32 cmr;
  48         u32 imr;
  49         u32 rc;
  50         bool clken;
  51 } tcb_cache[3];
  52 static u32 bmr_cache;
  53
  54 static u64 tc_get_cycles(struct clocksource *cs)
  55 {
  56         unsigned long   flags;
  57         u32             lower, upper;
  58
  59         raw_local_irq_save(flags);
  60         do {
  61                 upper = readl_relaxed(tcaddr + ATMEL_TC_REG(1, CV));
  62                 lower = readl_relaxed(tcaddr + ATMEL_TC_REG(0, CV));
  63         } while (upper != readl_relaxed(tcaddr + ATMEL_TC_REG(1, CV)));
  64
  65         raw_local_irq_restore(flags);
  66         return (upper << 16) | lower;
  67 }
  68
  69 static u64 tc_get_cycles32(struct clocksource *cs)
  70 {
  71         return readl_relaxed(tcaddr + ATMEL_TC_REG(0, CV));
  72 }
  73
  74 void tc_clksrc_suspend(struct clocksource *cs)
  75 {
  76         int i;
  77
  78         for (i = 0; i < ARRAY_SIZE(tcb_cache); i++) {
  79                 tcb_cache[i].cmr = readl(tcaddr + ATMEL_TC_REG(i, CMR));
  80                 tcb_cache[i].imr = readl(tcaddr + ATMEL_TC_REG(i, IMR));
  81                 tcb_cache[i].rc = readl(tcaddr + ATMEL_TC_REG(i, RC));
  82                 tcb_cache[i].clken = !!(readl(tcaddr + ATMEL_TC_REG(i, SR)) &
  83                                         ATMEL_TC_CLKSTA);
  84         }
  85
  86         bmr_cache = readl(tcaddr + ATMEL_TC_BMR);
  87 }
  88
  89 void tc_clksrc_resume(struct clocksource *cs)
  90 {
  91         int i;
  92
  93         for (i = 0; i < ARRAY_SIZE(tcb_cache); i++) {
  94                 /* Restore registers for the channel, RA and RB are not used  */
  95                 writel(tcb_cache[i].cmr, tcaddr + ATMEL_TC_REG(i, CMR));
  96                 writel(tcb_cache[i].rc, tcaddr + ATMEL_TC_REG(i, RC));
  97                 writel(0, tcaddr + ATMEL_TC_REG(i, RA));
  98                 writel(0, tcaddr + ATMEL_TC_REG(i, RB));
  99                 /* Disable all the interrupts */
 100                 writel(0xff, tcaddr + ATMEL_TC_REG(i, IDR));
 101                 /* Reenable interrupts that were enabled before suspending */
 102                 writel(tcb_cache[i].imr, tcaddr + ATMEL_TC_REG(i, IER));
 103                 /* Start the clock if it was used */
 104                 if (tcb_cache[i].clken)
 105                         writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(i, CCR));
 106         }
 107
 108         /* Dual channel, chain channels */
 109         writel(bmr_cache, tcaddr + ATMEL_TC_BMR);
 110         /* Finally, trigger all the channels*/
 111         writel(ATMEL_TC_SYNC, tcaddr + ATMEL_TC_BCR);
 112 }
 113
 114 static struct clocksource clksrc = {
 115         .name           = "tcb_clksrc",
 116         .rating         = 200,
 117         .read           = tc_get_cycles,
 118         .mask           = CLOCKSOURCE_MASK(32),
 119         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
 120         .suspend        = tc_clksrc_suspend,
 121         .resume         = tc_clksrc_resume,
 122 };
 123
 124 #ifdef CONFIG_GENERIC_CLOCKEVENTS
 125
 126 struct tc_clkevt_device {
 127         struct clock_event_device       clkevt;
 128         struct clk                      *clk;
 129         void __iomem                    *regs;
 130 };
 131
 132 static struct tc_clkevt_device *to_tc_clkevt(struct clock_event_device *clkevt)
 133 {
 134         return container_of(clkevt, struct tc_clkevt_device, clkevt);
 135 }
 136
 137 /* For now, we always use the 32K clock ... this optimizes for NO_HZ,
 138  * because using one of the divided clocks would usually mean the
 139  * tick rate can never be less than several dozen Hz (vs 0.5 Hz).
 140  *
 141  * A divided clock could be good for high resolution timers, since
 142  * 30.5 usec resolution can seem "low".
 143  */
 144 static u32 timer_clock;
 145
 146 static int tc_shutdown(struct clock_event_device *d)
 147 {
 148         struct tc_clkevt_device *tcd = to_tc_clkevt(d);
 149         void __iomem            *regs = tcd->regs;
 150
 151         writel(0xff, regs + ATMEL_TC_REG(2, IDR));
 152         writel(ATMEL_TC_CLKDIS, regs + ATMEL_TC_REG(2, CCR));
 153         if (!clockevent_state_detached(d))
 154                 clk_disable(tcd->clk);
 155
 156         return 0;
 157 }
 158
 159 static int tc_set_oneshot(struct clock_event_device *d)
 160 {
 161         struct tc_clkevt_device *tcd = to_tc_clkevt(d);
 162         void __iomem            *regs = tcd->regs;
 163
 164         if (clockevent_state_oneshot(d) || clockevent_state_periodic(d))
 165                 tc_shutdown(d);
 166
 167         clk_enable(tcd->clk);
 168
 169         /* slow clock, count up to RC, then irq and stop */
 170         writel(timer_clock | ATMEL_TC_CPCSTOP | ATMEL_TC_WAVE |
 171                      ATMEL_TC_WAVESEL_UP_AUTO, regs + ATMEL_TC_REG(2, CMR));
 172         writel(ATMEL_TC_CPCS, regs + ATMEL_TC_REG(2, IER));
 173
 174         /* set_next_event() configures and starts the timer */
 175         return 0;
 176 }
 177
 178 static int tc_set_periodic(struct clock_event_device *d)
 179 {
 180         struct tc_clkevt_device *tcd = to_tc_clkevt(d);
 181         void __iomem            *regs = tcd->regs;
 182
 183         if (clockevent_state_oneshot(d) || clockevent_state_periodic(d))
 184                 tc_shutdown(d);
 185
 186         /* By not making the gentime core emulate periodic mode on top
 187          * of oneshot, we get lower overhead and improved accuracy.
 188          */
 189         clk_enable(tcd->clk);
 190
 191         /* slow clock, count up to RC, then irq and restart */
 192         writel(timer_clock | ATMEL_TC_WAVE | ATMEL_TC_WAVESEL_UP_AUTO,
 193                      regs + ATMEL_TC_REG(2, CMR));
 194         writel((32768 + HZ / 2) / HZ, tcaddr + ATMEL_TC_REG(2, RC));
 195
 196         /* Enable clock and interrupts on RC compare */
 197         writel(ATMEL_TC_CPCS, regs + ATMEL_TC_REG(2, IER));
 198
 199         /* go go gadget! */
 200         writel(ATMEL_TC_CLKEN | ATMEL_TC_SWTRG, regs +
 201                      ATMEL_TC_REG(2, CCR));
 202         return 0;
 203 }
 204
 205 static int tc_next_event(unsigned long delta, struct clock_event_device *d)
 206 {
 207         writel_relaxed(delta, tcaddr + ATMEL_TC_REG(2, RC));
 208
 209         /* go go gadget! */
 210         writel_relaxed(ATMEL_TC_CLKEN | ATMEL_TC_SWTRG,
 211                         tcaddr + ATMEL_TC_REG(2, CCR));
 212         return 0;
 213 }
 214
 215 static struct tc_clkevt_device clkevt = {
 216         .clkevt = {
 217                 .name                   = "tc_clkevt",
 218                 .features               = CLOCK_EVT_FEAT_PERIODIC |
 219                                           CLOCK_EVT_FEAT_ONESHOT,
 220                 /* Should be lower than at91rm9200's system timer */
 221                 .rating                 = 125,
 222                 .set_next_event         = tc_next_event,
 223                 .set_state_shutdown     = tc_shutdown,
 224                 .set_state_periodic     = tc_set_periodic,
 225                 .set_state_oneshot      = tc_set_oneshot,
 226         },
 227 };
 228
 229 static irqreturn_t ch2_irq(int irq, void *handle)
 230 {
 231         struct tc_clkevt_device *dev = handle;
 232         unsigned int            sr;
 233
 234         sr = readl_relaxed(dev->regs + ATMEL_TC_REG(2, SR));
 235         if (sr & ATMEL_TC_CPCS) {
 236                 dev->clkevt.event_handler(&dev->clkevt);
 237                 return IRQ_HANDLED;
 238         }
 239
 240         return IRQ_NONE;
 241 }
 242
 243 static int __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
 244 {
 245         int ret;
 246         struct clk *t2_clk = tc->clk[2];
 247         int irq = tc->irq[2];
 248
 249         ret = clk_prepare_enable(tc->slow_clk);
 250         if (ret)
 251                 return ret;
 252
 253         /* try to enable t2 clk to avoid future errors in mode change */
 254         ret = clk_prepare_enable(t2_clk);
 255         if (ret) {
 256                 clk_disable_unprepare(tc->slow_clk);
 257                 return ret;
 258         }
 259
 260         clk_disable(t2_clk);
 261
 262         clkevt.regs = tc->regs;
 263         clkevt.clk = t2_clk;
 264
 265         timer_clock = clk32k_divisor_idx;
 266
 267         clkevt.clkevt.cpumask = cpumask_of(0);
 268
 269         ret = request_irq(irq, ch2_irq, IRQF_TIMER, "tc_clkevt", &clkevt);
 270         if (ret) {
 271                 clk_unprepare(t2_clk);
 272                 clk_disable_unprepare(tc->slow_clk);
 273                 return ret;
 274         }
 275
 276         clockevents_config_and_register(&clkevt.clkevt, 32768, 1, 0xffff);
 277
 278         return ret;
 279 }
 280
 281 #else /* !CONFIG_GENERIC_CLOCKEVENTS */
 282
 283 static int __init setup_clkevents(struct atmel_tc *tc, int clk32k_divisor_idx)
 284 {
 285         /* NOTHING */
 286         return 0;
 287 }
 288
 289 #endif
 290
 291 static void __init tcb_setup_dual_chan(struct atmel_tc *tc, int mck_divisor_idx)
 292 {
 293         /* channel 0:  waveform mode, input mclk/8, clock TIOA0 on overflow */
 294         writel(mck_divisor_idx                  /* likely divide-by-8 */
 295                         | ATMEL_TC_WAVE
 296                         | ATMEL_TC_WAVESEL_UP           /* free-run */
 297                         | ATMEL_TC_ACPA_SET             /* TIOA0 rises at 0 */
 298                         | ATMEL_TC_ACPC_CLEAR,          /* (duty cycle 50%) */
 299                         tcaddr + ATMEL_TC_REG(0, CMR));
 300         writel(0x0000, tcaddr + ATMEL_TC_REG(0, RA));
 301         writel(0x8000, tcaddr + ATMEL_TC_REG(0, RC));
 302         writel(0xff, tcaddr + ATMEL_TC_REG(0, IDR));    /* no irqs */
 303         writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(0, CCR));
 304
 305         /* channel 1:  waveform mode, input TIOA0 */
 306         writel(ATMEL_TC_XC1                     /* input: TIOA0 */
 307                         | ATMEL_TC_WAVE
 308                         | ATMEL_TC_WAVESEL_UP,          /* free-run */
 309                         tcaddr + ATMEL_TC_REG(1, CMR));
 310         writel(0xff, tcaddr + ATMEL_TC_REG(1, IDR));    /* no irqs */
 311         writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(1, CCR));
 312
 313         /* chain channel 0 to channel 1*/
 314         writel(ATMEL_TC_TC1XC1S_TIOA0, tcaddr + ATMEL_TC_BMR);
 315         /* then reset all the timers */
 316         writel(ATMEL_TC_SYNC, tcaddr + ATMEL_TC_BCR);
 317 }
 318
 319 static void __init tcb_setup_single_chan(struct atmel_tc *tc, int mck_divisor_idx)
 320 {
 321         /* channel 0:  waveform mode, input mclk/8 */
 322         writel(mck_divisor_idx                  /* likely divide-by-8 */
 323                         | ATMEL_TC_WAVE
 324                         | ATMEL_TC_WAVESEL_UP,          /* free-run */
 325                         tcaddr + ATMEL_TC_REG(0, CMR));
 326         writel(0xff, tcaddr + ATMEL_TC_REG(0, IDR));    /* no irqs */
 327         writel(ATMEL_TC_CLKEN, tcaddr + ATMEL_TC_REG(0, CCR));
 328
 329         /* then reset all the timers */
 330         writel(ATMEL_TC_SYNC, tcaddr + ATMEL_TC_BCR);
 331 }
 332
 333 static int __init tcb_clksrc_init(void)
 334 {
 335         static char bootinfo[] __initdata
 336                 = KERN_DEBUG "%s: tc%d at %d.%03d MHz\n";
 337
 338         struct platform_device *pdev;
 339         struct atmel_tc *tc;
 340         struct clk *t0_clk;
 341         u32 rate, divided_rate = 0;
 342         int best_divisor_idx = -1;
 343         int clk32k_divisor_idx = -1;
 344         int i;
 345         int ret;
 346
 347         tc = atmel_tc_alloc(CONFIG_ATMEL_TCB_CLKSRC_BLOCK);
 348         if (!tc) {
 349                 pr_debug("can't alloc TC for clocksource\n");
 350                 return -ENODEV;
 351         }
 352         tcaddr = tc->regs;
 353         pdev = tc->pdev;
 354
 355         t0_clk = tc->clk[0];
 356         ret = clk_prepare_enable(t0_clk);
 357         if (ret) {
 358                 pr_debug("can't enable T0 clk\n");
 359                 goto err_free_tc;
 360         }
 361
 362         /* How fast will we be counting?  Pick something over 5 MHz.  */
 363         rate = (u32) clk_get_rate(t0_clk);
 364         for (i = 0; i < 5; i++) {
 365                 unsigned divisor = atmel_tc_divisors[i];
 366                 unsigned tmp;
 367
 368                 /* remember 32 KiHz clock for later */
 369                 if (!divisor) {
 370                         clk32k_divisor_idx = i;
 371                         continue;
 372                 }
 373
 374                 tmp = rate / divisor;
 375                 pr_debug("TC: %u / %-3u [%d] --> %u\n", rate, divisor, i, tmp);
 376                 if (best_divisor_idx > 0) {
 377                         if (tmp < 5 * 1000 * 1000)
 378                                 continue;
 379                 }
 380                 divided_rate = tmp;
 381                 best_divisor_idx = i;
 382         }
 383
 384
 385         printk(bootinfo, clksrc.name, CONFIG_ATMEL_TCB_CLKSRC_BLOCK,
 386                         divided_rate / 1000000,
 387                         ((divided_rate + 500000) % 1000000) / 1000);
 388
 389         if (tc->tcb_config && tc->tcb_config->counter_width == 32) {
 390                 /* use apropriate function to read 32 bit counter */
 391                 clksrc.read = tc_get_cycles32;
 392                 /* setup ony channel 0 */
 393                 tcb_setup_single_chan(tc, best_divisor_idx);
 394         } else {
 395                 /* tclib will give us three clocks no matter what the
 396                  * underlying platform supports.
 397                  */
 398                 ret = clk_prepare_enable(tc->clk[1]);
 399                 if (ret) {
 400                         pr_debug("can't enable T1 clk\n");
 401                         goto err_disable_t0;
 402                 }
 403                 /* setup both channel 0 & 1 */
 404                 tcb_setup_dual_chan(tc, best_divisor_idx);
 405         }
 406
 407         /* and away we go! */
 408         ret = clocksource_register_hz(&clksrc, divided_rate);
 409         if (ret)
 410                 goto err_disable_t1;
 411
 412         /* channel 2:  periodic and oneshot timer support */
 413         ret = setup_clkevents(tc, clk32k_divisor_idx);
 414         if (ret)
 415                 goto err_unregister_clksrc;
 416
 417         return 0;
 418
 419 err_unregister_clksrc:
 420         clocksource_unregister(&clksrc);
 421
 422 err_disable_t1:
 423         if (!tc->tcb_config || tc->tcb_config->counter_width != 32)
 424                 clk_disable_unprepare(tc->clk[1]);
 425
 426 err_disable_t0:
 427         clk_disable_unprepare(t0_clk);
 428
 429 err_free_tc:
 430         atmel_tc_free(tc);
 431         return ret;
 432 }
 433 arch_initcall(tcb_clksrc_init);