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 & 0xff;
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 & 0xff;
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 /*
59 * a20r platform uses 2 counters to divide the input frequency.
60 * Counter 2 output is connected to Counter 0 & 1 input.
61 */
62 static void __init sni_a20r_timer_setup(void)
63 {
64 struct clock_event_device *cd = &a20r_clockevent_device;
65 unsigned int cpu = smp_processor_id();
66
67 cd->cpumask = cpumask_of(cpu);
68 clockevents_register_device(cd);
69 if (request_irq(SNI_A20R_IRQ_TIMER, a20r_interrupt,
70 IRQF_PERCPU | IRQF_TIMER, "a20r-timer", cd))
71 pr_err("Failed to register a20r-timer interrupt\n");
72 }
73
74 #define SNI_8254_TICK_RATE 1193182UL
75
76 #define SNI_8254_TCSAMP_COUNTER ((SNI_8254_TICK_RATE / HZ) + 255)
77
78 static __init unsigned long dosample(void)
79 {
80 u32 ct0, ct1;
81 volatile u8 msb;
82
83 /* Start the counter. */
84 outb_p(0x34, 0x43);
85 outb_p(SNI_8254_TCSAMP_COUNTER & 0xff, 0x40);
86 outb(SNI_8254_TCSAMP_COUNTER >> 8, 0x40);
87
88 /* Get initial counter invariant */
89 ct0 = read_c0_count();
90
91 /* Latch and spin until top byte of counter0 is zero */
92 do {
93 outb(0x00, 0x43);
94 (void) inb(0x40);
95 msb = inb(0x40);
96 ct1 = read_c0_count();
97 } while (msb);
98
99 /* Stop the counter. */
100 outb(0x38, 0x43);
101 /*
102 * Return the difference, this is how far the r4k counter increments
103 * for every 1/HZ seconds. We round off the nearest 1 MHz of master
104 * clock (= 1000000 / HZ / 2).
105 */
106 /*return (ct1 - ct0 + (500000/HZ/2)) / (500000/HZ) * (500000/HZ);*/
107 return (ct1 - ct0) / (500000/HZ) * (500000/HZ);
108 }
109
110 /*
111 * Here we need to calibrate the cycle counter to at least be close.
112 */
113 void __init plat_time_init(void)
114 {
115 unsigned long r4k_ticks[3];
116 unsigned long r4k_tick;
117
118 /*
119 * Figure out the r4k offset, the algorithm is very simple and works in
120 * _all_ cases as long as the 8254 counter register itself works ok (as
121 * an interrupt driving timer it does not because of bug, this is why
122 * we are using the onchip r4k counter/compare register to serve this
123 * purpose, but for r4k_offset calculation it will work ok for us).
124 * There are other very complicated ways of performing this calculation
125 * but this one works just fine so I am not going to futz around. ;-)
126 */
127 printk(KERN_INFO "Calibrating system timer... ");
128 dosample(); /* Prime cache. */
129 dosample(); /* Prime cache. */
130 /* Zero is NOT an option. */
131 do {
132 r4k_ticks[0] = dosample();
133 } while (!r4k_ticks[0]);
134 do {
135 r4k_ticks[1] = dosample();
136 } while (!r4k_ticks[1]);
137
138 if (r4k_ticks[0] != r4k_ticks[1]) {
139 printk("warning: timer counts differ, retrying... ");
140 r4k_ticks[2] = dosample();
141 if (r4k_ticks[2] == r4k_ticks[0]
142 || r4k_ticks[2] == r4k_ticks[1])
143 r4k_tick = r4k_ticks[2];
144 else {
145 printk("disagreement, using average... ");
146 r4k_tick = (r4k_ticks[0] + r4k_ticks[1]
147 + r4k_ticks[2]) / 3;
148 }
149 } else
150 r4k_tick = r4k_ticks[0];
151
152 printk("%d [%d.%04d MHz CPU]\n", (int) r4k_tick,
153 (int) (r4k_tick / (500000 / HZ)),
154 (int) (r4k_tick % (500000 / HZ)));
155
156 mips_hpt_frequency = r4k_tick * HZ;
157
158 switch (sni_brd_type) {
159 case SNI_BRD_10:
160 case SNI_BRD_10NEW:
161 case SNI_BRD_TOWER_OASIC:
162 case SNI_BRD_MINITOWER:
163 sni_a20r_timer_setup();
164 break;
165 }
166 setup_pit_timer();
167 }
168
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