1 #include <linux/types.h>
2 #include <linux/i8253.h>
3 #include <linux/interrupt.h>
6 #include <linux/time.h>
7 #include <linux/clockchips.h>
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)
16 static int a20r_set_periodic(struct clock_event_device *evt)
18 *(volatile u8 *)(A20R_PT_CLOCK_BASE + 12) = 0x34;
20 *(volatile u8 *)(A20R_PT_CLOCK_BASE + 0) = SNI_COUNTER0_DIV & 0xff;
22 *(volatile u8 *)(A20R_PT_CLOCK_BASE + 0) = SNI_COUNTER0_DIV >> 8;
25 *(volatile u8 *)(A20R_PT_CLOCK_BASE + 12) = 0xb4;
27 *(volatile u8 *)(A20R_PT_CLOCK_BASE + 8) = SNI_COUNTER2_DIV & 0xff;
29 *(volatile u8 *)(A20R_PT_CLOCK_BASE + 8) = SNI_COUNTER2_DIV >> 8;
34 static struct clock_event_device a20r_clockevent_device = {
36 .features = CLOCK_EVT_FEAT_PERIODIC,
38 /* .mult, .shift, .max_delta_ns and .min_delta_ns left uninitialized */
41 .irq = SNI_A20R_IRQ_TIMER,
42 .set_state_periodic = a20r_set_periodic,
45 static irqreturn_t a20r_interrupt(int irq, void *dev_id)
47 struct clock_event_device *cd = dev_id;
49 *(volatile u8 *)A20R_PT_TIM0_ACK = 0;
52 cd->event_handler(cd);
57 static struct irqaction a20r_irqaction = {
58 .handler = a20r_interrupt,
59 .flags = IRQF_PERCPU | IRQF_TIMER,
64 * a20r platform uses 2 counters to divide the input frequency.
65 * Counter 2 output is connected to Counter 0 & 1 input.
67 static void __init sni_a20r_timer_setup(void)
69 struct clock_event_device *cd = &a20r_clockevent_device;
70 struct irqaction *action = &a20r_irqaction;
71 unsigned int cpu = smp_processor_id();
73 cd->cpumask = cpumask_of(cpu);
74 clockevents_register_device(cd);
76 setup_irq(SNI_A20R_IRQ_TIMER, &a20r_irqaction);
79 #define SNI_8254_TICK_RATE 1193182UL
81 #define SNI_8254_TCSAMP_COUNTER ((SNI_8254_TICK_RATE / HZ) + 255)
83 static __init unsigned long dosample(void)
88 /* Start the counter. */
90 outb_p(SNI_8254_TCSAMP_COUNTER & 0xff, 0x40);
91 outb(SNI_8254_TCSAMP_COUNTER >> 8, 0x40);
93 /* Get initial counter invariant */
94 ct0 = read_c0_count();
96 /* Latch and spin until top byte of counter0 is zero */
101 ct1 = read_c0_count();
104 /* Stop the counter. */
107 * Return the difference, this is how far the r4k counter increments
108 * for every 1/HZ seconds. We round off the nearest 1 MHz of master
109 * clock (= 1000000 / HZ / 2).
111 /*return (ct1 - ct0 + (500000/HZ/2)) / (500000/HZ) * (500000/HZ);*/
112 return (ct1 - ct0) / (500000/HZ) * (500000/HZ);
116 * Here we need to calibrate the cycle counter to at least be close.
118 void __init plat_time_init(void)
120 unsigned long r4k_ticks[3];
121 unsigned long r4k_tick;
124 * Figure out the r4k offset, the algorithm is very simple and works in
125 * _all_ cases as long as the 8254 counter register itself works ok (as
126 * an interrupt driving timer it does not because of bug, this is why
127 * we are using the onchip r4k counter/compare register to serve this
128 * purpose, but for r4k_offset calculation it will work ok for us).
129 * There are other very complicated ways of performing this calculation
130 * but this one works just fine so I am not going to futz around. ;-)
132 printk(KERN_INFO "Calibrating system timer... ");
133 dosample(); /* Prime cache. */
134 dosample(); /* Prime cache. */
135 /* Zero is NOT an option. */
137 r4k_ticks[0] = dosample();
138 } while (!r4k_ticks[0]);
140 r4k_ticks[1] = dosample();
141 } while (!r4k_ticks[1]);
143 if (r4k_ticks[0] != r4k_ticks[1]) {
144 printk("warning: timer counts differ, retrying... ");
145 r4k_ticks[2] = dosample();
146 if (r4k_ticks[2] == r4k_ticks[0]
147 || r4k_ticks[2] == r4k_ticks[1])
148 r4k_tick = r4k_ticks[2];
150 printk("disagreement, using average... ");
151 r4k_tick = (r4k_ticks[0] + r4k_ticks[1]
155 r4k_tick = r4k_ticks[0];
157 printk("%d [%d.%04d MHz CPU]\n", (int) r4k_tick,
158 (int) (r4k_tick / (500000 / HZ)),
159 (int) (r4k_tick % (500000 / HZ)));
161 mips_hpt_frequency = r4k_tick * HZ;
163 switch (sni_brd_type) {
166 case SNI_BRD_TOWER_OASIC:
167 case SNI_BRD_MINITOWER:
168 sni_a20r_timer_setup();
174 void read_persistent_clock(struct timespec *ts)