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
31 static void __iomem *clksrc_dbx500_timer_base;
32
clksrc_dbx500_prcmu_read(struct clocksource * cs)33 static 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
47 static 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
dbx500_prcmu_sched_clock_read(void)57 static 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
clksrc_dbx500_prcmu_init(struct device_node * node)67 static 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 }
89 TIMER_OF_DECLARE(dbx500_prcmu, "stericsson,db8500-prcmu-timer-4",
90 clksrc_dbx500_prcmu_init);
91
