root/arch/mips/sni/time.c

DEFINITIONS

1. a20r_set_periodic
2. a20r_interrupt
3. sni_a20r_timer_setup
4. dosample
5. plat_time_init

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/types.h>
   3 #include <linux/i8253.h>
   4 #include <linux/interrupt.h>
   5 #include <linux/irq.h>
   6 #include <linux/smp.h>
   7 #include <linux/time.h>
   8 #include <linux/clockchips.h>
   9 
  10 #include <asm/sni.h>
  11 #include <asm/time.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 int a20r_set_periodic(struct clock_event_device *evt)
  18 {
  19         *(volatile u8 *)(A20R_PT_CLOCK_BASE + 12) = 0x34;
  20         wmb();
  21         *(volatile u8 *)(A20R_PT_CLOCK_BASE + 0) = SNI_COUNTER0_DIV;
  22         wmb();
  23         *(volatile u8 *)(A20R_PT_CLOCK_BASE + 0) = SNI_COUNTER0_DIV >> 8;
  24         wmb();
  25 
  26         *(volatile u8 *)(A20R_PT_CLOCK_BASE + 12) = 0xb4;
  27         wmb();
  28         *(volatile u8 *)(A20R_PT_CLOCK_BASE + 8) = SNI_COUNTER2_DIV;
  29         wmb();
  30         *(volatile u8 *)(A20R_PT_CLOCK_BASE + 8) = SNI_COUNTER2_DIV >> 8;
  31         wmb();
  32         return 0;
  33 }
  34 
  35 static struct clock_event_device a20r_clockevent_device = {
  36         .name                   = "a20r-timer",
  37         .features               = CLOCK_EVT_FEAT_PERIODIC,
  38 
  39         /* .mult, .shift, .max_delta_ns and .min_delta_ns left uninitialized */
  40 
  41         .rating                 = 300,
  42         .irq                    = SNI_A20R_IRQ_TIMER,
  43         .set_state_periodic     = a20r_set_periodic,
  44 };
  45 
  46 static irqreturn_t a20r_interrupt(int irq, void *dev_id)
  47 {
  48         struct clock_event_device *cd = dev_id;
  49 
  50         *(volatile u8 *)A20R_PT_TIM0_ACK = 0;
  51         wmb();
  52 
  53         cd->event_handler(cd);
  54 
  55         return IRQ_HANDLED;
  56 }
  57 
  58 static struct irqaction a20r_irqaction = {
  59         .handler        = a20r_interrupt,
  60         .flags          = IRQF_PERCPU | IRQF_TIMER,
  61         .name           = "a20r-timer",
  62 };
  63 
  64 /*
  65  * a20r platform uses 2 counters to divide the input frequency.
  66  * Counter 2 output is connected to Counter 0 & 1 input.
  67  */
  68 static void __init sni_a20r_timer_setup(void)
  69 {
  70         struct clock_event_device *cd = &a20r_clockevent_device;
  71         struct irqaction *action = &a20r_irqaction;
  72         unsigned int cpu = smp_processor_id();
  73 
  74         cd->cpumask             = cpumask_of(cpu);
  75         clockevents_register_device(cd);
  76         action->dev_id = cd;
  77         setup_irq(SNI_A20R_IRQ_TIMER, &a20r_irqaction);
  78 }
  79 
  80 #define SNI_8254_TICK_RATE        1193182UL
  81 
  82 #define SNI_8254_TCSAMP_COUNTER   ((SNI_8254_TICK_RATE / HZ) + 255)
  83 
  84 static __init unsigned long dosample(void)
  85 {
  86         u32 ct0, ct1;
  87         volatile u8 msb;
  88 
  89         /* Start the counter. */
  90         outb_p(0x34, 0x43);
  91         outb_p(SNI_8254_TCSAMP_COUNTER & 0xff, 0x40);
  92         outb(SNI_8254_TCSAMP_COUNTER >> 8, 0x40);
  93 
  94         /* Get initial counter invariant */
  95         ct0 = read_c0_count();
  96 
  97         /* Latch and spin until top byte of counter0 is zero */
  98         do {
  99                 outb(0x00, 0x43);
 100                 (void) inb(0x40);
 101                 msb = inb(0x40);
 102                 ct1 = read_c0_count();
 103         } while (msb);
 104 
 105         /* Stop the counter. */
 106         outb(0x38, 0x43);
 107         /*
 108          * Return the difference, this is how far the r4k counter increments
 109          * for every 1/HZ seconds. We round off the nearest 1 MHz of master
 110          * clock (= 1000000 / HZ / 2).
 111          */
 112         /*return (ct1 - ct0 + (500000/HZ/2)) / (500000/HZ) * (500000/HZ);*/
 113         return (ct1 - ct0) / (500000/HZ) * (500000/HZ);
 114 }
 115 
 116 /*
 117  * Here we need to calibrate the cycle counter to at least be close.
 118  */
 119 void __init plat_time_init(void)
 120 {
 121         unsigned long r4k_ticks[3];
 122         unsigned long r4k_tick;
 123 
 124         /*
 125          * Figure out the r4k offset, the algorithm is very simple and works in
 126          * _all_ cases as long as the 8254 counter register itself works ok (as
 127          * an interrupt driving timer it does not because of bug, this is why
 128          * we are using the onchip r4k counter/compare register to serve this
 129          * purpose, but for r4k_offset calculation it will work ok for us).
 130          * There are other very complicated ways of performing this calculation
 131          * but this one works just fine so I am not going to futz around. ;-)
 132          */
 133         printk(KERN_INFO "Calibrating system timer... ");
 134         dosample();     /* Prime cache. */
 135         dosample();     /* Prime cache. */
 136         /* Zero is NOT an option. */
 137         do {
 138                 r4k_ticks[0] = dosample();
 139         } while (!r4k_ticks[0]);
 140         do {
 141                 r4k_ticks[1] = dosample();
 142         } while (!r4k_ticks[1]);
 143 
 144         if (r4k_ticks[0] != r4k_ticks[1]) {
 145                 printk("warning: timer counts differ, retrying... ");
 146                 r4k_ticks[2] = dosample();
 147                 if (r4k_ticks[2] == r4k_ticks[0]
 148                     || r4k_ticks[2] == r4k_ticks[1])
 149                         r4k_tick = r4k_ticks[2];
 150                 else {
 151                         printk("disagreement, using average... ");
 152                         r4k_tick = (r4k_ticks[0] + r4k_ticks[1]
 153                                    + r4k_ticks[2]) / 3;
 154                 }
 155         } else
 156                 r4k_tick = r4k_ticks[0];
 157 
 158         printk("%d [%d.%04d MHz CPU]\n", (int) r4k_tick,
 159                 (int) (r4k_tick / (500000 / HZ)),
 160                 (int) (r4k_tick % (500000 / HZ)));
 161 
 162         mips_hpt_frequency = r4k_tick * HZ;
 163 
 164         switch (sni_brd_type) {
 165         case SNI_BRD_10:
 166         case SNI_BRD_10NEW:
 167         case SNI_BRD_TOWER_OASIC:
 168         case SNI_BRD_MINITOWER:
 169                 sni_a20r_timer_setup();
 170                 break;
 171         }
 172         setup_pit_timer();
 173 }