arch/mips/sni/time.c

   1 #include <linux/types.h>
   2 #include <linux/interrupt.h>
   3 #include <linux/irq.h>
   4 #include <linux/smp.h>
   5 #include <linux/time.h>
   6 #include <linux/clockchips.h>
   7
   8 #include <asm/i8253.h>
   9 #include <asm/sni.h>
  10 #include <asm/time.h>
  11 #include <asm-generic/rtc.h>
  12
  13 #define SNI_CLOCK_TICK_RATE     3686400
  14 #define SNI_COUNTER2_DIV        64
  15 #define SNI_COUNTER0_DIV        ((SNI_CLOCK_TICK_RATE / SNI_COUNTER2_DIV) / HZ)
  16
  17 static void a20r_set_mode(enum clock_event_mode mode,
  18                           struct clock_event_device *evt)
  19 {
  20         switch (mode) {
  21         case CLOCK_EVT_MODE_PERIODIC:
  22                 *(volatile u8 *)(A20R_PT_CLOCK_BASE + 12) = 0x34;
  23                 wmb();
  24                 *(volatile u8 *)(A20R_PT_CLOCK_BASE +  0) = SNI_COUNTER0_DIV;
  25                 wmb();
  26                 *(volatile u8 *)(A20R_PT_CLOCK_BASE +  0) = SNI_COUNTER0_DIV >> 8;
  27                 wmb();
  28
  29                 *(volatile u8 *)(A20R_PT_CLOCK_BASE + 12) = 0xb4;
  30                 wmb();
  31                 *(volatile u8 *)(A20R_PT_CLOCK_BASE +  8) = SNI_COUNTER2_DIV;
  32                 wmb();
  33                 *(volatile u8 *)(A20R_PT_CLOCK_BASE +  8) = SNI_COUNTER2_DIV >> 8;
  34                 wmb();
  35
  36                 break;
  37         case CLOCK_EVT_MODE_ONESHOT:
  38         case CLOCK_EVT_MODE_UNUSED:
  39         case CLOCK_EVT_MODE_SHUTDOWN:
  40                 break;
  41         case CLOCK_EVT_MODE_RESUME:
  42                 break;
  43         }
  44 }
  45
  46 static struct clock_event_device a20r_clockevent_device = {
  47         .name           = "a20r-timer",
  48         .features       = CLOCK_EVT_FEAT_PERIODIC,
  49
  50         /* .mult, .shift, .max_delta_ns and .min_delta_ns left uninitialized */
  51
  52         .rating         = 300,
  53         .irq            = SNI_A20R_IRQ_TIMER,
  54         .set_mode       = a20r_set_mode,
  55 };
  56
  57 static irqreturn_t a20r_interrupt(int irq, void *dev_id)
  58 {
  59         struct clock_event_device *cd = dev_id;
  60
  61         *(volatile u8 *)A20R_PT_TIM0_ACK = 0;
  62         wmb();
  63
  64         cd->event_handler(cd);
  65
  66         return IRQ_HANDLED;
  67 }
  68
  69 static struct irqaction a20r_irqaction = {
  70         .handler        = a20r_interrupt,
  71         .flags          = IRQF_DISABLED | IRQF_PERCPU | IRQF_TIMER,
  72         .name           = "a20r-timer",
  73 };
  74
  75 /*
  76  * a20r platform uses 2 counters to divide the input frequency.
  77  * Counter 2 output is connected to Counter 0 & 1 input.
  78  */
  79 static void __init sni_a20r_timer_setup(void)
  80 {
  81         struct clock_event_device *cd = &a20r_clockevent_device;
  82         struct irqaction *action = &a20r_irqaction;
  83         unsigned int cpu = smp_processor_id();
  84
  85         cd->cpumask             = cpumask_of(cpu);
  86         clockevents_register_device(cd);
  87         action->dev_id = cd;
  88         setup_irq(SNI_A20R_IRQ_TIMER, &a20r_irqaction);
  89 }
  90
  91 #define SNI_8254_TICK_RATE        1193182UL
  92
  93 #define SNI_8254_TCSAMP_COUNTER   ((SNI_8254_TICK_RATE / HZ) + 255)
  94
  95 static __init unsigned long dosample(void)
  96 {
  97         u32 ct0, ct1;
  98         volatile u8 msb, lsb;
  99
 100         /* Start the counter. */
 101         outb_p(0x34, 0x43);
 102         outb_p(SNI_8254_TCSAMP_COUNTER & 0xff, 0x40);
 103         outb(SNI_8254_TCSAMP_COUNTER >> 8, 0x40);
 104
 105         /* Get initial counter invariant */
 106         ct0 = read_c0_count();
 107
 108         /* Latch and spin until top byte of counter0 is zero */
 109         do {
 110                 outb(0x00, 0x43);
 111                 lsb = inb(0x40);
 112                 msb = inb(0x40);
 113                 ct1 = read_c0_count();
 114         } while (msb);
 115
 116         /* Stop the counter. */
 117         outb(0x38, 0x43);
 118         /*
 119          * Return the difference, this is how far the r4k counter increments
 120          * for every 1/HZ seconds. We round off the nearest 1 MHz of master
 121          * clock (= 1000000 / HZ / 2).
 122          */
 123         /*return (ct1 - ct0 + (500000/HZ/2)) / (500000/HZ) * (500000/HZ);*/
 124         return (ct1 - ct0) / (500000/HZ) * (500000/HZ);
 125 }
 126
 127 /*
 128  * Here we need to calibrate the cycle counter to at least be close.
 129  */
 130 void __init plat_time_init(void)
 131 {
 132         unsigned long r4k_ticks[3];
 133         unsigned long r4k_tick;
 134
 135         /*
 136          * Figure out the r4k offset, the algorithm is very simple and works in
 137          * _all_ cases as long as the 8254 counter register itself works ok (as
 138          * an interrupt driving timer it does not because of bug, this is why
 139          * we are using the onchip r4k counter/compare register to serve this
 140          * purpose, but for r4k_offset calculation it will work ok for us).
 141          * There are other very complicated ways of performing this calculation
 142          * but this one works just fine so I am not going to futz around. ;-)
 143          */
 144         printk(KERN_INFO "Calibrating system timer... ");
 145         dosample();     /* Prime cache. */
 146         dosample();     /* Prime cache. */
 147         /* Zero is NOT an option. */
 148         do {
 149                 r4k_ticks[0] = dosample();
 150         } while (!r4k_ticks[0]);
 151         do {
 152                 r4k_ticks[1] = dosample();
 153         } while (!r4k_ticks[1]);
 154
 155         if (r4k_ticks[0] != r4k_ticks[1]) {
 156                 printk("warning: timer counts differ, retrying... ");
 157                 r4k_ticks[2] = dosample();
 158                 if (r4k_ticks[2] == r4k_ticks[0]
 159                     || r4k_ticks[2] == r4k_ticks[1])
 160                         r4k_tick = r4k_ticks[2];
 161                 else {
 162                         printk("disagreement, using average... ");
 163                         r4k_tick = (r4k_ticks[0] + r4k_ticks[1]
 164                                    + r4k_ticks[2]) / 3;
 165                 }
 166         } else
 167                 r4k_tick = r4k_ticks[0];
 168
 169         printk("%d [%d.%04d MHz CPU]\n", (int) r4k_tick,
 170                 (int) (r4k_tick / (500000 / HZ)),
 171                 (int) (r4k_tick % (500000 / HZ)));
 172
 173         mips_hpt_frequency = r4k_tick * HZ;
 174
 175         switch (sni_brd_type) {
 176         case SNI_BRD_10:
 177         case SNI_BRD_10NEW:
 178         case SNI_BRD_TOWER_OASIC:
 179         case SNI_BRD_MINITOWER:
 180                 sni_a20r_timer_setup();
 181                 break;
 182         }
 183         setup_pit_timer();
 184 }
 185
 186 void read_persistent_clock(struct timespec *ts)
 187 {
 188         ts->tv_sec = -1;
 189         ts->tv_nsec = 0;
 190 }