1// SPDX-License-Identifier: GPL-2.0-only
 2/*
 3 * Copyright (C) ST-Ericsson SA 2011
 4 *
 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_CONTINUOUS	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 continuous 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_CONTINUOUS) {
64		writel(TIMER_MODE_CONTINUOUS,
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);