1/*
 2 * Copyright (C) ST-Ericsson SA 2011
 3 *
 4 * License Terms: GNU General Public License v2
 5 * Author: Mattias Wallin <mattias.wallin@stericsson.com> for ST-Ericsson
 6 * Author: Sundar Iyer for ST-Ericsson
 7 * sched_clock implementation is based on:
 8 * plat-nomadik/timer.c Linus Walleij <linus.walleij@stericsson.com>
 9 *
10 * DBx500-PRCMU Timer
11 * The PRCMU has 5 timers which are available in a always-on
12 * power domain.  We use the Timer 4 for our always-on clock
13 * source on DB8500 and Timer 3 on DB5500.
14 */
15#include <linux/clockchips.h>
16#include <linux/clksrc-dbx500-prcmu.h>
17
18#include <asm/sched_clock.h>
19
20#include <mach/setup.h>
21#include <mach/hardware.h>
22
23#define RATE_32K		32768
24
25#define TIMER_MODE_CONTINOUS	0x1
26#define TIMER_DOWNCOUNT_VAL	0xffffffff
27
28#define PRCMU_TIMER_REF		0
29#define PRCMU_TIMER_DOWNCOUNT	0x4
30#define PRCMU_TIMER_MODE	0x8
31
32#define SCHED_CLOCK_MIN_WRAP 131072 /* 2^32 / 32768 */
33
34static void __iomem *clksrc_dbx500_timer_base;
35
36static cycle_t clksrc_dbx500_prcmu_read(struct clocksource *cs)
37{
38	u32 count, count2;
39
40	do {
41		count = readl(clksrc_dbx500_timer_base +
42			      PRCMU_TIMER_DOWNCOUNT);
43		count2 = readl(clksrc_dbx500_timer_base +
44			       PRCMU_TIMER_DOWNCOUNT);
45	} while (count2 != count);
46
47	/* Negate because the timer is a decrementing counter */
48	return ~count;
49}
50
51static struct clocksource clocksource_dbx500_prcmu = {
52	.name		= "dbx500-prcmu-timer",
53	.rating		= 300,
54	.read		= clksrc_dbx500_prcmu_read,
55	.mask		= CLOCKSOURCE_MASK(32),
56	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
57};
58
59#ifdef CONFIG_CLKSRC_DBX500_PRCMU_SCHED_CLOCK
60
61static u32 notrace dbx500_prcmu_sched_clock_read(void)
62{
63	if (unlikely(!clksrc_dbx500_timer_base))
64		return 0;
65
66	return clksrc_dbx500_prcmu_read(&clocksource_dbx500_prcmu);
67}
68
69#endif
70
71void __init clksrc_dbx500_prcmu_init(void __iomem *base)
72{
73	clksrc_dbx500_timer_base = base;
74
75	/*
76	 * The A9 sub system expects the timer to be configured as
77	 * a continous looping timer.
78	 * The PRCMU should configure it but if it for some reason
79	 * don't we do it here.
80	 */
81	if (readl(clksrc_dbx500_timer_base + PRCMU_TIMER_MODE) !=
82	    TIMER_MODE_CONTINOUS) {
83		writel(TIMER_MODE_CONTINOUS,
84		       clksrc_dbx500_timer_base + PRCMU_TIMER_MODE);
85		writel(TIMER_DOWNCOUNT_VAL,
86		       clksrc_dbx500_timer_base + PRCMU_TIMER_REF);
87	}
88#ifdef CONFIG_CLKSRC_DBX500_PRCMU_SCHED_CLOCK
89	setup_sched_clock(dbx500_prcmu_sched_clock_read,
90			 32, RATE_32K);
91#endif
92	clocksource_register_hz(&clocksource_dbx500_prcmu, RATE_32K);
93}