drivers/clocksource/tcb_clksrc.c

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