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 | |
28 | static void __iomem *clksrc_dbx500_timer_base; |
29 | |
30 | static 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 | |
44 | static 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 | |
52 | static int __init clksrc_dbx500_prcmu_init(struct device_node *node) |
53 | { |
54 | clksrc_dbx500_timer_base = of_iomap(node, index: 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(addr: clksrc_dbx500_timer_base + PRCMU_TIMER_MODE) != |
63 | TIMER_MODE_CONTINUOUS) { |
64 | writel(TIMER_MODE_CONTINUOUS, |
65 | addr: clksrc_dbx500_timer_base + PRCMU_TIMER_MODE); |
66 | writel(TIMER_DOWNCOUNT_VAL, |
67 | addr: clksrc_dbx500_timer_base + PRCMU_TIMER_REF); |
68 | } |
69 | return clocksource_register_hz(cs: &clocksource_dbx500_prcmu, RATE_32K); |
70 | } |
71 | TIMER_OF_DECLARE(dbx500_prcmu, "stericsson,db8500-prcmu-timer-4" , |
72 | clksrc_dbx500_prcmu_init); |
73 | |