1/*
2 * This file is subject to the terms and conditions of the GNU General Public
3 * License.  See the file "COPYING" in the main directory of this archive
4 * for more details.
5 *
6 * Time operations for IP22 machines. Original code may come from
7 * Ralf Baechle or David S. Miller (sorry guys, i'm really not sure)
8 *
9 * Copyright (C) 2001 by Ladislav Michl
10 * Copyright (C) 2003, 06 Ralf Baechle (ralf@linux-mips.org)
11 */
12#include <linux/bcd.h>
13#include <linux/i8253.h>
14#include <linux/init.h>
15#include <linux/irq.h>
16#include <linux/kernel.h>
17#include <linux/interrupt.h>
18#include <linux/kernel_stat.h>
19#include <linux/time.h>
20#include <linux/ftrace.h>
21
22#include <asm/cpu.h>
23#include <asm/mipsregs.h>
24#include <asm/io.h>
25#include <asm/irq.h>
26#include <asm/time.h>
27#include <asm/sgialib.h>
28#include <asm/sgi/ioc.h>
29#include <asm/sgi/hpc3.h>
30#include <asm/sgi/ip22.h>
31
32static unsigned long dosample(void)
33{
34	u32 ct0, ct1;
35	u8 msb;
36
37	/* Start the counter. */
38	sgint->tcword = (SGINT_TCWORD_CNT2 | SGINT_TCWORD_CALL |
39			 SGINT_TCWORD_MRGEN);
40	sgint->tcnt2 = SGINT_TCSAMP_COUNTER & 0xff;
41	sgint->tcnt2 = SGINT_TCSAMP_COUNTER >> 8;
42
43	/* Get initial counter invariant */
44	ct0 = read_c0_count();
45
46	/* Latch and spin until top byte of counter2 is zero */
47	do {
48		writeb(SGINT_TCWORD_CNT2 | SGINT_TCWORD_CLAT, &sgint->tcword);
49		(void) readb(&sgint->tcnt2);
50		msb = readb(&sgint->tcnt2);
51		ct1 = read_c0_count();
52	} while (msb);
53
54	/* Stop the counter. */
55	writeb(SGINT_TCWORD_CNT2 | SGINT_TCWORD_CALL | SGINT_TCWORD_MSWST,
56	       &sgint->tcword);
57	/*
58	 * Return the difference, this is how far the r4k counter increments
59	 * for every 1/HZ seconds. We round off the nearest 1 MHz of master
60	 * clock (= 1000000 / HZ / 2).
61	 */
62
63	return (ct1 - ct0) / (500000/HZ) * (500000/HZ);
64}
65
66/*
67 * Here we need to calibrate the cycle counter to at least be close.
68 */
69__init void plat_time_init(void)
70{
71	unsigned long r4k_ticks[3];
72	unsigned long r4k_tick;
73
74	/*
75	 * Figure out the r4k offset, the algorithm is very simple and works in
76	 * _all_ cases as long as the 8254 counter register itself works ok (as
77	 * an interrupt driving timer it does not because of bug, this is why
78	 * we are using the onchip r4k counter/compare register to serve this
79	 * purpose, but for r4k_offset calculation it will work ok for us).
80	 * There are other very complicated ways of performing this calculation
81	 * but this one works just fine so I am not going to futz around. ;-)
82	 */
83	printk(KERN_INFO "Calibrating system timer... ");
84	dosample();	/* Prime cache. */
85	dosample();	/* Prime cache. */
86	/* Zero is NOT an option. */
87	do {
88		r4k_ticks[0] = dosample();
89	} while (!r4k_ticks[0]);
90	do {
91		r4k_ticks[1] = dosample();
92	} while (!r4k_ticks[1]);
93
94	if (r4k_ticks[0] != r4k_ticks[1]) {
95		printk("warning: timer counts differ, retrying... ");
96		r4k_ticks[2] = dosample();
97		if (r4k_ticks[2] == r4k_ticks[0]
98		    || r4k_ticks[2] == r4k_ticks[1])
99			r4k_tick = r4k_ticks[2];
100		else {
101			printk("disagreement, using average... ");
102			r4k_tick = (r4k_ticks[0] + r4k_ticks[1]
103				   + r4k_ticks[2]) / 3;
104		}
105	} else
106		r4k_tick = r4k_ticks[0];
107
108	printk("%d [%d.%04d MHz CPU]\n", (int) r4k_tick,
109		(int) (r4k_tick / (500000 / HZ)),
110		(int) (r4k_tick % (500000 / HZ)));
111
112	mips_hpt_frequency = r4k_tick * HZ;
113
114	if (ip22_is_fullhouse())
115		setup_pit_timer();
116}
117
118/* Generic SGI handler for (spurious) 8254 interrupts */
119void __irq_entry indy_8254timer_irq(void)
120{
121	int irq = SGI_8254_0_IRQ;
122	ULONG cnt;
123	char c;
124
125	irq_enter();
126	kstat_incr_irq_this_cpu(irq);
127	printk(KERN_ALERT "Oops, got 8254 interrupt.\n");
128	ArcRead(0, &c, 1, &cnt);
129	ArcEnterInteractiveMode();
130	irq_exit();
131}
132