summaryrefslogtreecommitdiffstats
path: root/arch/mips/sgi-ip22/ip22-time.c
blob: 6071924493353c96c3c69560f90ab2488d49c617 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Time operations for IP22 machines. Original code may come from
 * Ralf Baechle or David S. Miller (sorry guys, i'm really not sure)
 *
 * Copyright (C) 2001 by Ladislav Michl
 * Copyright (C) 2003, 06 Ralf Baechle (ralf@linux-mips.org)
 */
#include <linux/bcd.h>
#include <linux/i8253.h>
#include <linux/init.h>
#include <linux/irq.h>
#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/kernel_stat.h>
#include <linux/time.h>
#include <linux/ftrace.h>

#include <asm/cpu.h>
#include <asm/mipsregs.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/time.h>
#include <asm/sgialib.h>
#include <asm/sgi/ioc.h>
#include <asm/sgi/hpc3.h>
#include <asm/sgi/ip22.h>

static unsigned long dosample(void)
{
	u32 ct0, ct1;
	u8 msb;

	/* Start the counter. */
	sgint->tcword = (SGINT_TCWORD_CNT2 | SGINT_TCWORD_CALL |
			 SGINT_TCWORD_MRGEN);
	sgint->tcnt2 = SGINT_TCSAMP_COUNTER & 0xff;
	sgint->tcnt2 = SGINT_TCSAMP_COUNTER >> 8;

	/* Get initial counter invariant */
	ct0 = read_c0_count();

	/* Latch and spin until top byte of counter2 is zero */
	do {
		writeb(SGINT_TCWORD_CNT2 | SGINT_TCWORD_CLAT, &sgint->tcword);
		(void) readb(&sgint->tcnt2);
		msb = readb(&sgint->tcnt2);
		ct1 = read_c0_count();
	} while (msb);

	/* Stop the counter. */
	writeb(SGINT_TCWORD_CNT2 | SGINT_TCWORD_CALL | SGINT_TCWORD_MSWST,
	       &sgint->tcword);
	/*
	 * Return the difference, this is how far the r4k counter increments
	 * for every 1/HZ seconds. We round off the nearest 1 MHz of master
	 * clock (= 1000000 / HZ / 2).
	 */

	return (ct1 - ct0) / (500000/HZ) * (500000/HZ);
}

/*
 * Here we need to calibrate the cycle counter to at least be close.
 */
__init void plat_time_init(void)
{
	unsigned long r4k_ticks[3];
	unsigned long r4k_tick;

	/*
	 * Figure out the r4k offset, the algorithm is very simple and works in
	 * _all_ cases as long as the 8254 counter register itself works ok (as
	 * an interrupt driving timer it does not because of bug, this is why
	 * we are using the onchip r4k counter/compare register to serve this
	 * purpose, but for r4k_offset calculation it will work ok for us).
	 * There are other very complicated ways of performing this calculation
	 * but this one works just fine so I am not going to futz around. ;-)
	 */
	printk(KERN_INFO "Calibrating system timer... ");
	dosample();	/* Prime cache. */
	dosample();	/* Prime cache. */
	/* Zero is NOT an option. */
	do {
		r4k_ticks[0] = dosample();
	} while (!r4k_ticks[0]);
	do {
		r4k_ticks[1] = dosample();
	} while (!r4k_ticks[1]);

	if (r4k_ticks[0] != r4k_ticks[1]) {
		printk("warning: timer counts differ, retrying... ");
		r4k_ticks[2] = dosample();
		if (r4k_ticks[2] == r4k_ticks[0]
		    || r4k_ticks[2] == r4k_ticks[1])
			r4k_tick = r4k_ticks[2];
		else {
			printk("disagreement, using average... ");
			r4k_tick = (r4k_ticks[0] + r4k_ticks[1]
				   + r4k_ticks[2]) / 3;
		}
	} else
		r4k_tick = r4k_ticks[0];

	printk("%d [%d.%04d MHz CPU]\n", (int) r4k_tick,
		(int) (r4k_tick / (500000 / HZ)),
		(int) (r4k_tick % (500000 / HZ)));

	mips_hpt_frequency = r4k_tick * HZ;

	if (ip22_is_fullhouse())
		setup_pit_timer();
}

/* Generic SGI handler for (spurious) 8254 interrupts */
void __irq_entry indy_8254timer_irq(void)
{
	int irq = SGI_8254_0_IRQ;
	ULONG cnt;
	char c;

	irq_enter();
	kstat_incr_irqs_this_cpu(irq, irq_to_desc(irq));
	printk(KERN_ALERT "Oops, got 8254 interrupt.\n");
	ArcRead(0, &c, 1, &cnt);
	ArcEnterInteractiveMode();
	irq_exit();
}