arch/mips/sni/time.c

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