arch/blackfin/kernel/time-ts.c

   1 /*
   2  * linux/arch/kernel/time-ts.c
   3  *
   4  * Based on arm clockevents implementation and old bfin time tick.
   5  *
   6  * Copyright(C) 2008, GeoTechnologies, Vitja Makarov
   7  *
   8  * This code is licenced under the GPL version 2. For details see
   9  * kernel-base/COPYING.
  10  */
  11 #include <linux/module.h>
  12 #include <linux/profile.h>
  13 #include <linux/interrupt.h>
  14 #include <linux/time.h>
  15 #include <linux/timex.h>
  16 #include <linux/irq.h>
  17 #include <linux/clocksource.h>
  18 #include <linux/clockchips.h>
  19 #include <linux/cpufreq.h>
  20
  21 #include <asm/blackfin.h>
  22 #include <asm/time.h>
  23
  24 #ifdef CONFIG_CYCLES_CLOCKSOURCE
  25
  26 /* Accelerators for sched_clock()
  27  * convert from cycles(64bits) => nanoseconds (64bits)
  28  *  basic equation:
  29  *              ns = cycles / (freq / ns_per_sec)
  30  *              ns = cycles * (ns_per_sec / freq)
  31  *              ns = cycles * (10^9 / (cpu_khz * 10^3))
  32  *              ns = cycles * (10^6 / cpu_khz)
  33  *
  34  *      Then we use scaling math (suggested by george@mvista.com) to get:
  35  *              ns = cycles * (10^6 * SC / cpu_khz) / SC
  36  *              ns = cycles * cyc2ns_scale / SC
  37  *
  38  *      And since SC is a constant power of two, we can convert the div
  39  *  into a shift.
  40  *
  41  *  We can use khz divisor instead of mhz to keep a better precision, since
  42  *  cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
  43  *  (mathieu.desnoyers@polymtl.ca)
  44  *
  45  *                      -johnstul@us.ibm.com "math is hard, lets go shopping!"
  46  */
  47
  48 static unsigned long cyc2ns_scale;
  49 #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
  50
  51 static inline void set_cyc2ns_scale(unsigned long cpu_khz)
  52 {
  53         cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR) / cpu_khz;
  54 }
  55
  56 static inline unsigned long long cycles_2_ns(cycle_t cyc)
  57 {
  58         return (cyc * cyc2ns_scale) >> CYC2NS_SCALE_FACTOR;
  59 }
  60
  61 static cycle_t read_cycles(void)
  62 {
  63         return __bfin_cycles_off + (get_cycles() << __bfin_cycles_mod);
  64 }
  65
  66 unsigned long long sched_clock(void)
  67 {
  68         return cycles_2_ns(read_cycles());
  69 }
  70
  71 static struct clocksource clocksource_bfin = {
  72         .name           = "bfin_cycles",
  73         .rating         = 350,
  74         .read           = read_cycles,
  75         .mask           = CLOCKSOURCE_MASK(64),
  76         .shift          = 22,
  77         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  78 };
  79
  80 static int __init bfin_clocksource_init(void)
  81 {
  82         set_cyc2ns_scale(get_cclk() / 1000);
  83
  84         clocksource_bfin.mult = clocksource_hz2mult(get_cclk(), clocksource_bfin.shift);
  85
  86         if (clocksource_register(&clocksource_bfin))
  87                 panic("failed to register clocksource");
  88
  89         return 0;
  90 }
  91
  92 #else
  93 # define bfin_clocksource_init()
  94 #endif
  95
  96 static int bfin_timer_set_next_event(unsigned long cycles,
  97                                      struct clock_event_device *evt)
  98 {
  99         bfin_write_TCOUNT(cycles);
 100         CSYNC();
 101         return 0;
 102 }
 103
 104 static void bfin_timer_set_mode(enum clock_event_mode mode,
 105                                 struct clock_event_device *evt)
 106 {
 107         switch (mode) {
 108         case CLOCK_EVT_MODE_PERIODIC: {
 109                 unsigned long tcount = ((get_cclk() / (HZ * TIME_SCALE)) - 1);
 110                 bfin_write_TCNTL(TMPWR);
 111                 bfin_write_TSCALE(TIME_SCALE - 1);
 112                 CSYNC();
 113                 bfin_write_TPERIOD(tcount);
 114                 bfin_write_TCOUNT(tcount);
 115                 bfin_write_TCNTL(TMPWR | TMREN | TAUTORLD);
 116                 CSYNC();
 117                 break;
 118         }
 119         case CLOCK_EVT_MODE_ONESHOT:
 120                 bfin_write_TSCALE(TIME_SCALE - 1);
 121                 bfin_write_TCOUNT(0);
 122                 bfin_write_TCNTL(TMPWR | TMREN);
 123                 CSYNC();
 124                 break;
 125         case CLOCK_EVT_MODE_UNUSED:
 126         case CLOCK_EVT_MODE_SHUTDOWN:
 127                 bfin_write_TCNTL(0);
 128                 CSYNC();
 129                 break;
 130         case CLOCK_EVT_MODE_RESUME:
 131                 break;
 132         }
 133 }
 134
 135 static void __init bfin_timer_init(void)
 136 {
 137         /* power up the timer, but don't enable it just yet */
 138         bfin_write_TCNTL(TMPWR);
 139         CSYNC();
 140
 141         /*
 142          * the TSCALE prescaler counter.
 143          */
 144         bfin_write_TSCALE(TIME_SCALE - 1);
 145         bfin_write_TPERIOD(0);
 146         bfin_write_TCOUNT(0);
 147
 148         /* now enable the timer */
 149         CSYNC();
 150 }
 151
 152 /*
 153  * timer_interrupt() needs to keep up the real-time clock,
 154  * as well as call the "do_timer()" routine every clocktick
 155  */
 156 #ifdef CONFIG_CORE_TIMER_IRQ_L1
 157 __attribute__((l1_text))
 158 #endif
 159 irqreturn_t timer_interrupt(int irq, void *dev_id);
 160
 161 static struct clock_event_device clockevent_bfin = {
 162         .name           = "bfin_core_timer",
 163         .features       = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
 164         .shift          = 32,
 165         .set_next_event = bfin_timer_set_next_event,
 166         .set_mode       = bfin_timer_set_mode,
 167 };
 168
 169 static struct irqaction bfin_timer_irq = {
 170         .name           = "Blackfin Core Timer",
 171         .flags          = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
 172         .handler        = timer_interrupt,
 173         .dev_id         = &clockevent_bfin,
 174 };
 175
 176 irqreturn_t timer_interrupt(int irq, void *dev_id)
 177 {
 178         struct clock_event_device *evt = dev_id;
 179         evt->event_handler(evt);
 180         return IRQ_HANDLED;
 181 }
 182
 183 static int __init bfin_clockevent_init(void)
 184 {
 185         unsigned long timer_clk;
 186
 187         timer_clk = get_cclk() / TIME_SCALE;
 188
 189         setup_irq(IRQ_CORETMR, &bfin_timer_irq);
 190         bfin_timer_init();
 191
 192         clockevent_bfin.mult = div_sc(timer_clk, NSEC_PER_SEC, clockevent_bfin.shift);
 193         clockevent_bfin.max_delta_ns = clockevent_delta2ns(-1, &clockevent_bfin);
 194         clockevent_bfin.min_delta_ns = clockevent_delta2ns(100, &clockevent_bfin);
 195         clockevent_bfin.cpumask = cpumask_of(0);
 196         clockevents_register_device(&clockevent_bfin);
 197
 198         return 0;
 199 }
 200
 201 void __init time_init(void)
 202 {
 203         time_t secs_since_1970 = (365 * 37 + 9) * 24 * 60 * 60; /* 1 Jan 2007 */
 204
 205 #ifdef CONFIG_RTC_DRV_BFIN
 206         /* [#2663] hack to filter junk RTC values that would cause
 207          * userspace to have to deal with time values greater than
 208          * 2^31 seconds (which uClibc cannot cope with yet)
 209          */
 210         if ((bfin_read_RTC_STAT() & 0xC0000000) == 0xC0000000) {
 211                 printk(KERN_NOTICE "bfin-rtc: invalid date; resetting\n");
 212                 bfin_write_RTC_STAT(0);
 213         }
 214 #endif
 215
 216         /* Initialize xtime. From now on, xtime is updated with timer interrupts */
 217         xtime.tv_sec = secs_since_1970;
 218         xtime.tv_nsec = 0;
 219         set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);
 220
 221         bfin_clocksource_init();
 222         bfin_clockevent_init();
 223 }