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(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((adj & 0xffff0000) >> 16, AICA_RTC_SECS_H); 69 __raw_writel((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, "rtc-generic", -1, 91 &rtc_generic_ops, 92 sizeof(rtc_generic_ops)); 93 94 return PTR_ERR_OR_ZERO(pdev); 95 } 96 arch_initcall(aica_time_init); 97