From 85d0b3a573d8b711ee0c96199ac24a0f3283ed68 Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Sat, 13 Jul 2013 15:49:45 -0700 Subject: alpha: Reorganize rtc handling Discontinue use of GENERIC_CMOS_UPDATE; rely on the RTC subsystem. The marvel platform requires that the rtc only be touched from the boot cpu. This had been partially implemented with hooks for get/set_rtc_time, but read/update_persistent_clock were not handled. Move the hooks from the machine_vec to a special rtc_class_ops struct. We had read_persistent_clock managing the epoch against which the rtc hw is based, but this didn't apply to get_rtc_time or set_rtc_time. This resulted in incorrect values when hwclock(8) gets involved. Allow the epoch to be set from the kernel command-line, overriding the autodetection, which is doomed to fail in 2020. Further, by implementing the rtc ioctl function, we can expose this epoch to userland. Elide the alarm functions that RTC_DRV_CMOS implements. This was highly questionable on Alpha, since the interrupt is used by the system timer. Signed-off-by: Richard Henderson --- arch/alpha/Kconfig | 1 - arch/alpha/include/asm/machvec.h | 4 +- arch/alpha/include/asm/rtc.h | 11 -- arch/alpha/kernel/Makefile | 1 + arch/alpha/kernel/machvec_impl.h | 5 +- arch/alpha/kernel/proto.h | 2 - arch/alpha/kernel/rtc.c | 323 +++++++++++++++++++++++++++++++++++++++ arch/alpha/kernel/sys_jensen.c | 2 - arch/alpha/kernel/sys_marvel.c | 55 +------ arch/alpha/kernel/time.c | 146 +----------------- 10 files changed, 328 insertions(+), 222 deletions(-) create mode 100644 arch/alpha/kernel/rtc.c (limited to 'arch/alpha') diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig index f9e84da4971..5d863d171b9 100644 --- a/arch/alpha/Kconfig +++ b/arch/alpha/Kconfig @@ -17,7 +17,6 @@ config ALPHA select ARCH_HAVE_NMI_SAFE_CMPXCHG select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE select GENERIC_SMP_IDLE_THREAD - select GENERIC_CMOS_UPDATE select GENERIC_STRNCPY_FROM_USER select GENERIC_STRNLEN_USER select HAVE_MOD_ARCH_SPECIFIC diff --git a/arch/alpha/include/asm/machvec.h b/arch/alpha/include/asm/machvec.h index 4ac90167d34..75cb3641ed2 100644 --- a/arch/alpha/include/asm/machvec.h +++ b/arch/alpha/include/asm/machvec.h @@ -33,6 +33,7 @@ struct alpha_machine_vector int nr_irqs; int rtc_port; + int rtc_boot_cpu_only; unsigned int max_asn; unsigned long max_isa_dma_address; unsigned long irq_probe_mask; @@ -95,9 +96,6 @@ struct alpha_machine_vector struct _alpha_agp_info *(*agp_info)(void); - unsigned int (*rtc_get_time)(struct rtc_time *); - int (*rtc_set_time)(struct rtc_time *); - const char *vector_name; /* NUMA information */ diff --git a/arch/alpha/include/asm/rtc.h b/arch/alpha/include/asm/rtc.h index d70408d3667..f71c3b0ed36 100644 --- a/arch/alpha/include/asm/rtc.h +++ b/arch/alpha/include/asm/rtc.h @@ -1,12 +1 @@ -#ifndef _ALPHA_RTC_H -#define _ALPHA_RTC_H - -#if defined(CONFIG_ALPHA_MARVEL) && defined(CONFIG_SMP) \ - || defined(CONFIG_ALPHA_GENERIC) -# define get_rtc_time alpha_mv.rtc_get_time -# define set_rtc_time alpha_mv.rtc_set_time -#endif - #include - -#endif diff --git a/arch/alpha/kernel/Makefile b/arch/alpha/kernel/Makefile index 84ec46b38f7..0d54650e78f 100644 --- a/arch/alpha/kernel/Makefile +++ b/arch/alpha/kernel/Makefile @@ -16,6 +16,7 @@ obj-$(CONFIG_PCI) += pci.o pci_iommu.o pci-sysfs.o obj-$(CONFIG_SRM_ENV) += srm_env.o obj-$(CONFIG_MODULES) += module.o obj-$(CONFIG_PERF_EVENTS) += perf_event.o +obj-$(CONFIG_RTC_DRV_ALPHA) += rtc.o ifdef CONFIG_ALPHA_GENERIC diff --git a/arch/alpha/kernel/machvec_impl.h b/arch/alpha/kernel/machvec_impl.h index 7fa62488bd1..f54bdf658cd 100644 --- a/arch/alpha/kernel/machvec_impl.h +++ b/arch/alpha/kernel/machvec_impl.h @@ -43,10 +43,7 @@ #define CAT1(x,y) x##y #define CAT(x,y) CAT1(x,y) -#define DO_DEFAULT_RTC \ - .rtc_port = 0x70, \ - .rtc_get_time = common_get_rtc_time, \ - .rtc_set_time = common_set_rtc_time +#define DO_DEFAULT_RTC .rtc_port = 0x70 #define DO_EV4_MMU \ .max_asn = EV4_MAX_ASN, \ diff --git a/arch/alpha/kernel/proto.h b/arch/alpha/kernel/proto.h index d3e52d3fd59..3b250fa5f2c 100644 --- a/arch/alpha/kernel/proto.h +++ b/arch/alpha/kernel/proto.h @@ -144,8 +144,6 @@ extern void smp_percpu_timer_interrupt(struct pt_regs *); extern irqreturn_t timer_interrupt(int irq, void *dev); extern void common_init_rtc(void); extern unsigned long est_cycle_freq; -extern unsigned int common_get_rtc_time(struct rtc_time *time); -extern int common_set_rtc_time(struct rtc_time *time); /* smc37c93x.c */ extern void SMC93x_Init(void); diff --git a/arch/alpha/kernel/rtc.c b/arch/alpha/kernel/rtc.c new file mode 100644 index 00000000000..c8d284d8521 --- /dev/null +++ b/arch/alpha/kernel/rtc.c @@ -0,0 +1,323 @@ +/* + * linux/arch/alpha/kernel/rtc.c + * + * Copyright (C) 1991, 1992, 1995, 1999, 2000 Linus Torvalds + * + * This file contains date handling. + */ +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +#include "proto.h" + + +/* + * Support for the RTC device. + * + * We don't want to use the rtc-cmos driver, because we don't want to support + * alarms, as that would be indistinguishable from timer interrupts. + * + * Further, generic code is really, really tied to a 1900 epoch. This is + * true in __get_rtc_time as well as the users of struct rtc_time e.g. + * rtc_tm_to_time. Thankfully all of the other epochs in use are later + * than 1900, and so it's easy to adjust. + */ + +static unsigned long rtc_epoch; + +static int __init +specifiy_epoch(char *str) +{ + unsigned long epoch = simple_strtoul(str, NULL, 0); + if (epoch < 1900) + printk("Ignoring invalid user specified epoch %lu\n", epoch); + else + rtc_epoch = epoch; + return 1; +} +__setup("epoch=", specifiy_epoch); + +static void __init +init_rtc_epoch(void) +{ + int epoch, year, ctrl; + + if (rtc_epoch != 0) { + /* The epoch was specified on the command-line. */ + return; + } + + /* Detect the epoch in use on this computer. */ + ctrl = CMOS_READ(RTC_CONTROL); + year = CMOS_READ(RTC_YEAR); + if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD) + year = bcd2bin(year); + + /* PC-like is standard; used for year >= 70 */ + epoch = 1900; + if (year < 20) { + epoch = 2000; + } else if (year >= 20 && year < 48) { + /* NT epoch */ + epoch = 1980; + } else if (year >= 48 && year < 70) { + /* Digital UNIX epoch */ + epoch = 1952; + } + rtc_epoch = epoch; + + printk(KERN_INFO "Using epoch %d for rtc year %d\n", epoch, year); +} + +static int +alpha_rtc_read_time(struct device *dev, struct rtc_time *tm) +{ + __get_rtc_time(tm); + + /* Adjust for non-default epochs. It's easier to depend on the + generic __get_rtc_time and adjust the epoch here than create + a copy of __get_rtc_time with the edits we need. */ + if (rtc_epoch != 1900) { + int year = tm->tm_year; + /* Undo the century adjustment made in __get_rtc_time. */ + if (year >= 100) + year -= 100; + year += rtc_epoch - 1900; + /* Redo the century adjustment with the epoch in place. */ + if (year <= 69) + year += 100; + tm->tm_year = year; + } + + return rtc_valid_tm(tm); +} + +static int +alpha_rtc_set_time(struct device *dev, struct rtc_time *tm) +{ + struct rtc_time xtm; + + if (rtc_epoch != 1900) { + xtm = *tm; + xtm.tm_year -= rtc_epoch - 1900; + tm = &xtm; + } + + return __set_rtc_time(tm); +} + +static int +alpha_rtc_set_mmss(struct device *dev, unsigned long nowtime) +{ + int retval = 0; + int real_seconds, real_minutes, cmos_minutes; + unsigned char save_control, save_freq_select; + + /* Note: This code only updates minutes and seconds. Comments + indicate this was to avoid messing with unknown time zones, + and with the epoch nonsense described above. In order for + this to work, the existing clock cannot be off by more than + 15 minutes. + + ??? This choice is may be out of date. The x86 port does + not have problems with timezones, and the epoch processing has + now been fixed in alpha_set_rtc_time. + + In either case, one can always force a full rtc update with + the userland hwclock program, so surely 15 minute accuracy + is no real burden. */ + + /* In order to set the CMOS clock precisely, we have to be called + 500 ms after the second nowtime has started, because when + nowtime is written into the registers of the CMOS clock, it will + jump to the next second precisely 500 ms later. Check the Motorola + MC146818A or Dallas DS12887 data sheet for details. */ + + /* irq are locally disabled here */ + spin_lock(&rtc_lock); + /* Tell the clock it's being set */ + save_control = CMOS_READ(RTC_CONTROL); + CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL); + + /* Stop and reset prescaler */ + save_freq_select = CMOS_READ(RTC_FREQ_SELECT); + CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT); + + cmos_minutes = CMOS_READ(RTC_MINUTES); + if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) + cmos_minutes = bcd2bin(cmos_minutes); + + real_seconds = nowtime % 60; + real_minutes = nowtime / 60; + if (((abs(real_minutes - cmos_minutes) + 15) / 30) & 1) { + /* correct for half hour time zone */ + real_minutes += 30; + } + real_minutes %= 60; + + if (abs(real_minutes - cmos_minutes) < 30) { + if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) { + real_seconds = bin2bcd(real_seconds); + real_minutes = bin2bcd(real_minutes); + } + CMOS_WRITE(real_seconds,RTC_SECONDS); + CMOS_WRITE(real_minutes,RTC_MINUTES); + } else { + printk_once(KERN_NOTICE + "set_rtc_mmss: can't update from %d to %d\n", + cmos_minutes, real_minutes); + retval = -1; + } + + /* The following flags have to be released exactly in this order, + * otherwise the DS12887 (popular MC146818A clone with integrated + * battery and quartz) will not reset the oscillator and will not + * update precisely 500 ms later. You won't find this mentioned in + * the Dallas Semiconductor data sheets, but who believes data + * sheets anyway ... -- Markus Kuhn + */ + CMOS_WRITE(save_control, RTC_CONTROL); + CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT); + spin_unlock(&rtc_lock); + + return retval; +} + +static int +alpha_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg) +{ + switch (cmd) { + case RTC_EPOCH_READ: + return put_user(rtc_epoch, (unsigned long __user *)arg); + case RTC_EPOCH_SET: + if (arg < 1900) + return -EINVAL; + rtc_epoch = arg; + return 0; + default: + return -ENOIOCTLCMD; + } +} + +static const struct rtc_class_ops alpha_rtc_ops = { + .read_time = alpha_rtc_read_time, + .set_time = alpha_rtc_set_time, + .set_mmss = alpha_rtc_set_mmss, + .ioctl = alpha_rtc_ioctl, +}; + +/* + * Similarly, except do the actual CMOS access on the boot cpu only. + * This requires marshalling the data across an interprocessor call. + */ + +#if defined(CONFIG_SMP) && \ + (defined(CONFIG_ALPHA_GENERIC) || defined(CONFIG_ALPHA_MARVEL)) +# define HAVE_REMOTE_RTC 1 + +union remote_data { + struct rtc_time *tm; + unsigned long now; + long retval; +}; + +static void +do_remote_read(void *data) +{ + union remote_data *x = data; + x->retval = alpha_rtc_read_time(NULL, x->tm); +} + +static int +remote_read_time(struct device *dev, struct rtc_time *tm) +{ + union remote_data x; + if (smp_processor_id() != boot_cpuid) { + x.tm = tm; + smp_call_function_single(boot_cpuid, do_remote_read, &x, 1); + return x.retval; + } + return alpha_rtc_read_time(NULL, tm); +} + +static void +do_remote_set(void *data) +{ + union remote_data *x = data; + x->retval = alpha_rtc_set_time(NULL, x->tm); +} + +static int +remote_set_time(struct device *dev, struct rtc_time *tm) +{ + union remote_data x; + if (smp_processor_id() != boot_cpuid) { + x.tm = tm; + smp_call_function_single(boot_cpuid, do_remote_set, &x, 1); + return x.retval; + } + return alpha_rtc_set_time(NULL, tm); +} + +static void +do_remote_mmss(void *data) +{ + union remote_data *x = data; + x->retval = alpha_rtc_set_mmss(NULL, x->now); +} + +static int +remote_set_mmss(struct device *dev, unsigned long now) +{ + union remote_data x; + if (smp_processor_id() != boot_cpuid) { + x.now = now; + smp_call_function_single(boot_cpuid, do_remote_mmss, &x, 1); + return x.retval; + } + return alpha_rtc_set_mmss(NULL, now); +} + +static const struct rtc_class_ops remote_rtc_ops = { + .read_time = remote_read_time, + .set_time = remote_set_time, + .set_mmss = remote_set_mmss, + .ioctl = alpha_rtc_ioctl, +}; +#endif + +static int __init +alpha_rtc_init(void) +{ + const struct rtc_class_ops *ops; + struct platform_device *pdev; + struct rtc_device *rtc; + const char *name; + + init_rtc_epoch(); + name = "rtc-alpha"; + ops = &alpha_rtc_ops; + +#ifdef HAVE_REMOTE_RTC + if (alpha_mv.rtc_boot_cpu_only) + ops = &remote_rtc_ops; +#endif + + pdev = platform_device_register_simple(name, -1, NULL, 0); + rtc = devm_rtc_device_register(&pdev->dev, name, ops, THIS_MODULE); + if (IS_ERR(rtc)) + return PTR_ERR(rtc); + + platform_set_drvdata(pdev, rtc); + return 0; +} +device_initcall(alpha_rtc_init); diff --git a/arch/alpha/kernel/sys_jensen.c b/arch/alpha/kernel/sys_jensen.c index 5a0af11b3a6..608f2a7fa0a 100644 --- a/arch/alpha/kernel/sys_jensen.c +++ b/arch/alpha/kernel/sys_jensen.c @@ -224,8 +224,6 @@ struct alpha_machine_vector jensen_mv __initmv = { .machine_check = jensen_machine_check, .max_isa_dma_address = ALPHA_MAX_ISA_DMA_ADDRESS, .rtc_port = 0x170, - .rtc_get_time = common_get_rtc_time, - .rtc_set_time = common_set_rtc_time, .nr_irqs = 16, .device_interrupt = jensen_device_interrupt, diff --git a/arch/alpha/kernel/sys_marvel.c b/arch/alpha/kernel/sys_marvel.c index c92e389ff21..f21d61fab67 100644 --- a/arch/alpha/kernel/sys_marvel.c +++ b/arch/alpha/kernel/sys_marvel.c @@ -22,7 +22,6 @@ #include #include #include -#include #include "proto.h" #include "err_impl.h" @@ -400,57 +399,6 @@ marvel_init_rtc(void) init_rtc_irq(); } -struct marvel_rtc_time { - struct rtc_time *time; - int retval; -}; - -#ifdef CONFIG_SMP -static void -smp_get_rtc_time(void *data) -{ - struct marvel_rtc_time *mrt = data; - mrt->retval = __get_rtc_time(mrt->time); -} - -static void -smp_set_rtc_time(void *data) -{ - struct marvel_rtc_time *mrt = data; - mrt->retval = __set_rtc_time(mrt->time); -} -#endif - -static unsigned int -marvel_get_rtc_time(struct rtc_time *time) -{ -#ifdef CONFIG_SMP - struct marvel_rtc_time mrt; - - if (smp_processor_id() != boot_cpuid) { - mrt.time = time; - smp_call_function_single(boot_cpuid, smp_get_rtc_time, &mrt, 1); - return mrt.retval; - } -#endif - return __get_rtc_time(time); -} - -static int -marvel_set_rtc_time(struct rtc_time *time) -{ -#ifdef CONFIG_SMP - struct marvel_rtc_time mrt; - - if (smp_processor_id() != boot_cpuid) { - mrt.time = time; - smp_call_function_single(boot_cpuid, smp_set_rtc_time, &mrt, 1); - return mrt.retval; - } -#endif - return __set_rtc_time(time); -} - static void marvel_smp_callin(void) { @@ -492,8 +440,7 @@ struct alpha_machine_vector marvel_ev7_mv __initmv = { .vector_name = "MARVEL/EV7", DO_EV7_MMU, .rtc_port = 0x70, - .rtc_get_time = marvel_get_rtc_time, - .rtc_set_time = marvel_set_rtc_time, + .rtc_boot_cpu_only = 1, DO_MARVEL_IO, .machine_check = marvel_machine_check, .max_isa_dma_address = ALPHA_MAX_ISA_DMA_ADDRESS, diff --git a/arch/alpha/kernel/time.c b/arch/alpha/kernel/time.c index a6bcb3113d8..4c6c0fe47a7 100644 --- a/arch/alpha/kernel/time.c +++ b/arch/alpha/kernel/time.c @@ -3,13 +3,7 @@ * * Copyright (C) 1991, 1992, 1995, 1999, 2000 Linus Torvalds * - * This file contains the PC-specific time handling details: - * reading the RTC at bootup, etc.. - * 1994-07-02 Alan Modra - * fixed set_rtc_mmss, fixed time.year for >= 2000, new mktime - * 1995-03-26 Markus Kuhn - * fixed 500 ms bug at call to set_rtc_mmss, fixed DS12887 - * precision CMOS clock update + * This file contains the clocksource time handling. * 1997-09-10 Updated NTP code according to technical memorandum Jan '96 * "A Kernel Model for Precision Timekeeping" by Dave Mills * 1997-01-09 Adrian Sun @@ -21,9 +15,6 @@ * 1999-04-16 Thorsten Kranzkowski (dl8bcu@gmx.net) * fixed algorithm in do_gettimeofday() for calculating the precise time * from processor cycle counter (now taking lost_ticks into account) - * 2000-08-13 Jan-Benedict Glaw - * Fixed time_init to be aware of epoches != 1900. This prevents - * booting up in 2048 for me;) Code is stolen from rtc.c. * 2003-06-03 R. Scott Bailey * Tighten sanity in time_init from 1% (10,000 PPM) to 250 PPM */ @@ -46,7 +37,6 @@ #include #include #include -#include #include #include @@ -56,8 +46,6 @@ #include "proto.h" #include "irq_impl.h" -static int set_rtc_mmss(unsigned long); - DEFINE_SPINLOCK(rtc_lock); EXPORT_SYMBOL(rtc_lock); @@ -108,53 +96,6 @@ static inline __u32 rpcc(void) return __builtin_alpha_rpcc(); } -int update_persistent_clock(struct timespec now) -{ - return set_rtc_mmss(now.tv_sec); -} - -void read_persistent_clock(struct timespec *ts) -{ - unsigned int year, mon, day, hour, min, sec, epoch; - - sec = CMOS_READ(RTC_SECONDS); - min = CMOS_READ(RTC_MINUTES); - hour = CMOS_READ(RTC_HOURS); - day = CMOS_READ(RTC_DAY_OF_MONTH); - mon = CMOS_READ(RTC_MONTH); - year = CMOS_READ(RTC_YEAR); - - if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD) { - sec = bcd2bin(sec); - min = bcd2bin(min); - hour = bcd2bin(hour); - day = bcd2bin(day); - mon = bcd2bin(mon); - year = bcd2bin(year); - } - - /* PC-like is standard; used for year >= 70 */ - epoch = 1900; - if (year < 20) - epoch = 2000; - else if (year >= 20 && year < 48) - /* NT epoch */ - epoch = 1980; - else if (year >= 48 && year < 70) - /* Digital UNIX epoch */ - epoch = 1952; - - printk(KERN_INFO "Using epoch = %d\n", epoch); - - if ((year += epoch) < 1970) - year += 100; - - ts->tv_sec = mktime(year, mon, day, hour, min, sec); - ts->tv_nsec = 0; -} - - - /* * timer_interrupt() needs to keep up the real-time clock, * as well as call the "xtime_update()" routine every clocktick @@ -243,16 +184,6 @@ common_init_rtc(void) init_rtc_irq(); } -unsigned int common_get_rtc_time(struct rtc_time *time) -{ - return __get_rtc_time(time); -} - -int common_set_rtc_time(struct rtc_time *time) -{ - return __set_rtc_time(time); -} - /* Validate a computed cycle counter result against the known bounds for the given processor core. There's too much brokenness in the way of timing hardware for any one method to work everywhere. :-( @@ -453,78 +384,3 @@ time_init(void) /* Startup the timer source. */ alpha_mv.init_rtc(); } - -/* - * In order to set the CMOS clock precisely, set_rtc_mmss has to be - * called 500 ms after the second nowtime has started, because when - * nowtime is written into the registers of the CMOS clock, it will - * jump to the next second precisely 500 ms later. Check the Motorola - * MC146818A or Dallas DS12887 data sheet for details. - * - * BUG: This routine does not handle hour overflow properly; it just - * sets the minutes. Usually you won't notice until after reboot! - */ - - -static int -set_rtc_mmss(unsigned long nowtime) -{ - int retval = 0; - int real_seconds, real_minutes, cmos_minutes; - unsigned char save_control, save_freq_select; - - /* irq are locally disabled here */ - spin_lock(&rtc_lock); - /* Tell the clock it's being set */ - save_control = CMOS_READ(RTC_CONTROL); - CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL); - - /* Stop and reset prescaler */ - save_freq_select = CMOS_READ(RTC_FREQ_SELECT); - CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT); - - cmos_minutes = CMOS_READ(RTC_MINUTES); - if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) - cmos_minutes = bcd2bin(cmos_minutes); - - /* - * since we're only adjusting minutes and seconds, - * don't interfere with hour overflow. This avoids - * messing with unknown time zones but requires your - * RTC not to be off by more than 15 minutes - */ - real_seconds = nowtime % 60; - real_minutes = nowtime / 60; - if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1) { - /* correct for half hour time zone */ - real_minutes += 30; - } - real_minutes %= 60; - - if (abs(real_minutes - cmos_minutes) < 30) { - if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) { - real_seconds = bin2bcd(real_seconds); - real_minutes = bin2bcd(real_minutes); - } - CMOS_WRITE(real_seconds,RTC_SECONDS); - CMOS_WRITE(real_minutes,RTC_MINUTES); - } else { - printk_once(KERN_NOTICE - "set_rtc_mmss: can't update from %d to %d\n", - cmos_minutes, real_minutes); - retval = -1; - } - - /* The following flags have to be released exactly in this order, - * otherwise the DS12887 (popular MC146818A clone with integrated - * battery and quartz) will not reset the oscillator and will not - * update precisely 500 ms later. You won't find this mentioned in - * the Dallas Semiconductor data sheets, but who believes data - * sheets anyway ... -- Markus Kuhn - */ - CMOS_WRITE(save_control, RTC_CONTROL); - CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT); - spin_unlock(&rtc_lock); - - return retval; -} -- cgit v1.2.3-18-g5258