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.
14 */
15#include <linux/of.h>
16#include <linux/of_address.h>
17#include <linux/clockchips.h>
18#include <linux/sched_clock.h>
19
20#define RATE_32K		32768
21
22#define TIMER_MODE_CONTINOUS	0x1
23#define TIMER_DOWNCOUNT_VAL	0xffffffff
24
25#define PRCMU_TIMER_REF		0
26#define PRCMU_TIMER_DOWNCOUNT	0x4
27#define PRCMU_TIMER_MODE	0x8
28
29#define SCHED_CLOCK_MIN_WRAP 131072 /* 2^32 / 32768 */
30
31static void __iomem *clksrc_dbx500_timer_base;
32
33static u64 notrace clksrc_dbx500_prcmu_read(struct clocksource *cs)
34{
35	void __iomem *base = clksrc_dbx500_timer_base;
36	u32 count, count2;
37
38	do {
39		count = readl_relaxed(base + PRCMU_TIMER_DOWNCOUNT);
40		count2 = readl_relaxed(base + PRCMU_TIMER_DOWNCOUNT);
41	} while (count2 != count);
42
43	/* Negate because the timer is a decrementing counter */
44	return ~count;
45}
46
47static struct clocksource clocksource_dbx500_prcmu = {
48	.name		= "dbx500-prcmu-timer",
49	.rating		= 300,
50	.read		= clksrc_dbx500_prcmu_read,
51	.mask		= CLOCKSOURCE_MASK(32),
52	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
53};
54
55#ifdef CONFIG_CLKSRC_DBX500_PRCMU_SCHED_CLOCK
56
57static u64 notrace dbx500_prcmu_sched_clock_read(void)
58{
59	if (unlikely(!clksrc_dbx500_timer_base))
60		return 0;
61
62	return clksrc_dbx500_prcmu_read(&clocksource_dbx500_prcmu);
63}
64
65#endif
66
67static int __init clksrc_dbx500_prcmu_init(struct device_node *node)
68{
69	clksrc_dbx500_timer_base = of_iomap(node, 0);
70
71	/*
72	 * The A9 sub system expects the timer to be configured as
73	 * a continous looping timer.
74	 * The PRCMU should configure it but if it for some reason
75	 * don't we do it here.
76	 */
77	if (readl(clksrc_dbx500_timer_base + PRCMU_TIMER_MODE) !=
78	    TIMER_MODE_CONTINOUS) {
79		writel(TIMER_MODE_CONTINOUS,
80		       clksrc_dbx500_timer_base + PRCMU_TIMER_MODE);
81		writel(TIMER_DOWNCOUNT_VAL,
82		       clksrc_dbx500_timer_base + PRCMU_TIMER_REF);
83	}
84#ifdef CONFIG_CLKSRC_DBX500_PRCMU_SCHED_CLOCK
85	sched_clock_register(dbx500_prcmu_sched_clock_read, 32, RATE_32K);
86#endif
87	return clocksource_register_hz(&clocksource_dbx500_prcmu, RATE_32K);
88}
89CLOCKSOURCE_OF_DECLARE(dbx500_prcmu, "stericsson,db8500-prcmu-timer-4",
90		       clksrc_dbx500_prcmu_init);