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
19#define RATE_32K 32768
20
21#define TIMER_MODE_CONTINOUS 0x1
22#define TIMER_DOWNCOUNT_VAL 0xffffffff
23
24#define PRCMU_TIMER_REF 0
25#define PRCMU_TIMER_DOWNCOUNT 0x4
26#define PRCMU_TIMER_MODE 0x8
27
28static void __iomem *clksrc_dbx500_timer_base;
29
30static u64 notrace clksrc_dbx500_prcmu_read(struct clocksource *cs)
31{
32 void __iomem *base = clksrc_dbx500_timer_base;
33 u32 count, count2;
34
35 do {
36 count = readl_relaxed(base + PRCMU_TIMER_DOWNCOUNT);
37 count2 = readl_relaxed(base + PRCMU_TIMER_DOWNCOUNT);
38 } while (count2 != count);
39
40 /* Negate because the timer is a decrementing counter */
41 return ~count;
42}
43
44static struct clocksource clocksource_dbx500_prcmu = {
45 .name = "dbx500-prcmu-timer",
46 .rating = 100,
47 .read = clksrc_dbx500_prcmu_read,
48 .mask = CLOCKSOURCE_MASK(32),
49 .flags = CLOCK_SOURCE_IS_CONTINUOUS | CLOCK_SOURCE_SUSPEND_NONSTOP,
50};
51
52static int __init clksrc_dbx500_prcmu_init(struct device_node *node)
53{
54 clksrc_dbx500_timer_base = of_iomap(node, 0);
55
56 /*
57 * The A9 sub system expects the timer to be configured as
58 * a continous looping timer.
59 * The PRCMU should configure it but if it for some reason
60 * don't we do it here.
61 */
62 if (readl(clksrc_dbx500_timer_base + PRCMU_TIMER_MODE) !=
63 TIMER_MODE_CONTINOUS) {
64 writel(TIMER_MODE_CONTINOUS,
65 clksrc_dbx500_timer_base + PRCMU_TIMER_MODE);
66 writel(TIMER_DOWNCOUNT_VAL,
67 clksrc_dbx500_timer_base + PRCMU_TIMER_REF);
68 }
69 return clocksource_register_hz(&clocksource_dbx500_prcmu, RATE_32K);
70}
71TIMER_OF_DECLARE(dbx500_prcmu, "stericsson,db8500-prcmu-timer-4",
72 clksrc_dbx500_prcmu_init);
73