1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * arch/sh/boards/dreamcast/rtc.c |
4 | * |
5 | * Dreamcast AICA RTC routines. |
6 | * |
7 | * Copyright (c) 2001, 2002 M. R. Brown <mrbrown@0xd6.org> |
8 | * Copyright (c) 2002 Paul Mundt <lethal@chaoticdreams.org> |
9 | */ |
10 | |
11 | #include <linux/time.h> |
12 | #include <linux/rtc.h> |
13 | #include <linux/io.h> |
14 | #include <linux/platform_device.h> |
15 | |
16 | /* The AICA RTC has an Epoch of 1/1/1950, so we must subtract 20 years (in |
17 | seconds) to get the standard Unix Epoch when getting the time, and add |
18 | 20 years when setting the time. */ |
19 | #define TWENTY_YEARS ((20 * 365LU + 5) * 86400) |
20 | |
21 | /* The AICA RTC is represented by a 32-bit seconds counter stored in 2 16-bit |
22 | registers.*/ |
23 | #define AICA_RTC_SECS_H 0xa0710000 |
24 | #define AICA_RTC_SECS_L 0xa0710004 |
25 | |
26 | /** |
27 | * aica_rtc_gettimeofday - Get the time from the AICA RTC |
28 | * @dev: the RTC device (ignored) |
29 | * @tm: pointer to resulting RTC time structure |
30 | * |
31 | * Grabs the current RTC seconds counter and adjusts it to the Unix Epoch. |
32 | */ |
33 | static int aica_rtc_gettimeofday(struct device *dev, struct rtc_time *tm) |
34 | { |
35 | unsigned long val1, val2; |
36 | time64_t t; |
37 | |
38 | do { |
39 | val1 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) | |
40 | (__raw_readl(AICA_RTC_SECS_L) & 0xffff); |
41 | |
42 | val2 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) | |
43 | (__raw_readl(AICA_RTC_SECS_L) & 0xffff); |
44 | } while (val1 != val2); |
45 | |
46 | /* normalize to 1970..2106 time range */ |
47 | t = (u32)(val1 - TWENTY_YEARS); |
48 | |
49 | rtc_time64_to_tm(time: t, tm); |
50 | |
51 | return 0; |
52 | } |
53 | |
54 | /** |
55 | * aica_rtc_settimeofday - Set the AICA RTC to the current time |
56 | * @dev: the RTC device (ignored) |
57 | * @tm: pointer to new RTC time structure |
58 | * |
59 | * Adjusts the given @tv to the AICA Epoch and sets the RTC seconds counter. |
60 | */ |
61 | static int aica_rtc_settimeofday(struct device *dev, struct rtc_time *tm) |
62 | { |
63 | unsigned long val1, val2; |
64 | time64_t secs = rtc_tm_to_time64(tm); |
65 | u32 adj = secs + TWENTY_YEARS; |
66 | |
67 | do { |
68 | __raw_writel(val: (adj & 0xffff0000) >> 16, AICA_RTC_SECS_H); |
69 | __raw_writel(val: (adj & 0xffff), AICA_RTC_SECS_L); |
70 | |
71 | val1 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) | |
72 | (__raw_readl(AICA_RTC_SECS_L) & 0xffff); |
73 | |
74 | val2 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) | |
75 | (__raw_readl(AICA_RTC_SECS_L) & 0xffff); |
76 | } while (val1 != val2); |
77 | |
78 | return 0; |
79 | } |
80 | |
81 | static const struct rtc_class_ops rtc_generic_ops = { |
82 | .read_time = aica_rtc_gettimeofday, |
83 | .set_time = aica_rtc_settimeofday, |
84 | }; |
85 | |
86 | static int __init aica_time_init(void) |
87 | { |
88 | struct platform_device *pdev; |
89 | |
90 | pdev = platform_device_register_data(NULL, name: "rtc-generic" , id: -1, |
91 | data: &rtc_generic_ops, |
92 | size: sizeof(rtc_generic_ops)); |
93 | |
94 | return PTR_ERR_OR_ZERO(ptr: pdev); |
95 | } |
96 | arch_initcall(aica_time_init); |
97 | |