The dreamcast RTC support has an extra level of indirection to provide either the old read_persistent_clock/update_persistent_clock interface or the rtc-generic device for hctosys/systohc.

Both do the same thing here, so we can do away with the abstraction and simply enable the RTC core code to take care of it.

Signed-off-by: Arnd Bergmann arnd@arndb.de --- arch/sh/boards/mach-dreamcast/Makefile | 4 +- arch/sh/boards/mach-dreamcast/rtc.c | 39 +++++++++++++------ arch/sh/boards/mach-dreamcast/setup.c | 1 - arch/sh/configs/dreamcast_defconfig | 2 + arch/sh/include/mach-dreamcast/mach/sysasic.h | 1 - 5 files changed, 31 insertions(+), 16 deletions(-)

diff --git a/arch/sh/boards/mach-dreamcast/Makefile b/arch/sh/boards/mach-dreamcast/Makefile index 7b97546c7e5f..62b024bc2a3e 100644 --- a/arch/sh/boards/mach-dreamcast/Makefile +++ b/arch/sh/boards/mach-dreamcast/Makefile @@ -2,5 +2,5 @@ # Makefile for the Sega Dreamcast specific parts of the kernel #

-obj-y := setup.o irq.o rtc.o - +obj-y := setup.o irq.o +obj-$(CONFIG_RTC_DRV_GENERIC) += rtc.o diff --git a/arch/sh/boards/mach-dreamcast/rtc.c b/arch/sh/boards/mach-dreamcast/rtc.c index 061d65714fcc..4f168d8d2951 100644 --- a/arch/sh/boards/mach-dreamcast/rtc.c +++ b/arch/sh/boards/mach-dreamcast/rtc.c @@ -11,8 +11,9 @@ */

#include <linux/time.h> -#include <asm/rtc.h> -#include <asm/io.h> +#include <linux/rtc.h> +#include <linux/io.h> +#include <linux/platform_device.h>

/* The AICA RTC has an Epoch of 1/1/1950, so we must subtract 20 years (in seconds) to get the standard Unix Epoch when getting the time, and add @@ -30,9 +31,10 @@ * * Grabs the current RTC seconds counter and adjusts it to the Unix Epoch. */ -static void aica_rtc_gettimeofday(struct timespec *ts) +static int aica_rtc_gettimeofday(struct device *dev, struct rtc_time *tm) { unsigned long val1, val2; + time64_t t;

do { val1 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) | @@ -42,10 +44,12 @@ static void aica_rtc_gettimeofday(struct timespec *ts) (__raw_readl(AICA_RTC_SECS_L) & 0xffff); } while (val1 != val2);

- ts->tv_sec = val1 - TWENTY_YEARS; + /* normalize to 1970..2106 time range */ + t = (u32)(val1 - TWENTY_YEARS);

- /* Can't get nanoseconds with just a seconds counter. */ - ts->tv_nsec = 0; + rtc_time64_to_tm(t, tm); + + return 0; }

/** @@ -54,10 +58,11 @@ static void aica_rtc_gettimeofday(struct timespec *ts) * * Adjusts the given @tv to the AICA Epoch and sets the RTC seconds counter. */ -static int aica_rtc_settimeofday(const time_t secs) +static int aica_rtc_settimeofday(struct device *dev, struct rtc_time *tm) { unsigned long val1, val2; - unsigned long adj = secs + TWENTY_YEARS; + time64_t secs = rtc_tm_to_time64(tm); + u32 adj = secs + TWENTY_YEARS;

do { __raw_writel((adj & 0xffff0000) >> 16, AICA_RTC_SECS_H); @@ -73,9 +78,19 @@ static int aica_rtc_settimeofday(const time_t secs) return 0; }

-void aica_time_init(void) +static const struct rtc_class_ops rtc_generic_ops = { + .read_time = aica_rtc_gettimeofday, + .set_time = aica_rtc_settimeofday, +}; + +static int __init aica_time_init(void) { - rtc_sh_get_time = aica_rtc_gettimeofday; - rtc_sh_set_time = aica_rtc_settimeofday; -} + struct platform_device *pdev; + + pdev = platform_device_register_data(NULL, "rtc-generic", -1, + &rtc_generic_ops, + sizeof(rtc_generic_ops));

+ return PTR_ERR_OR_ZERO(pdev); +} +arch_initcall(aica_time_init); diff --git a/arch/sh/boards/mach-dreamcast/setup.c b/arch/sh/boards/mach-dreamcast/setup.c index ad1a4db72e04..672c2ad8f8d5 100644 --- a/arch/sh/boards/mach-dreamcast/setup.c +++ b/arch/sh/boards/mach-dreamcast/setup.c @@ -30,7 +30,6 @@

static void __init dreamcast_setup(char **cmdline_p) { - board_time_init = aica_time_init; }

static struct sh_machine_vector mv_dreamcast __initmv = { diff --git a/arch/sh/configs/dreamcast_defconfig b/arch/sh/configs/dreamcast_defconfig index 3f08dc54480b..1d27666c029f 100644 --- a/arch/sh/configs/dreamcast_defconfig +++ b/arch/sh/configs/dreamcast_defconfig @@ -70,3 +70,5 @@ CONFIG_PROC_KCORE=y CONFIG_TMPFS=y CONFIG_HUGETLBFS=y # CONFIG_CRYPTO_ANSI_CPRNG is not set +CONFIG_RTC_CLASS=y +CONFIG_RTC_DRV_GENERIC=y diff --git a/arch/sh/include/mach-dreamcast/mach/sysasic.h b/arch/sh/include/mach-dreamcast/mach/sysasic.h index 58f710e1ebc2..59effd1ed3e1 100644 --- a/arch/sh/include/mach-dreamcast/mach/sysasic.h +++ b/arch/sh/include/mach-dreamcast/mach/sysasic.h @@ -42,7 +42,6 @@ /* arch/sh/boards/mach-dreamcast/irq.c */ extern int systemasic_irq_demux(int); extern void systemasic_irq_init(void); -extern void aica_time_init(void);

#endif /* __ASM_SH_DREAMCAST_SYSASIC_H */

All platforms are now converted to RTC drivers, so this has become obsolete. The board_time_init() callback still has one caller, but could otherwise also get killed.

This removes one more usage of the deprecated timespec structure, which overflows in y2038.

Signed-off-by: Arnd Bergmann arnd@arndb.de --- arch/sh/include/asm/rtc.h | 2 -- arch/sh/kernel/time.c | 69 --------------------------------------- 2 files changed, 71 deletions(-)

diff --git a/arch/sh/include/asm/rtc.h b/arch/sh/include/asm/rtc.h index c63555ee1255..fe55fbb181aa 100644 --- a/arch/sh/include/asm/rtc.h +++ b/arch/sh/include/asm/rtc.h @@ -4,8 +4,6 @@

void time_init(void); extern void (*board_time_init)(void); -extern void (*rtc_sh_get_time)(struct timespec *); -extern int (*rtc_sh_set_time)(const time_t);

#define RTC_CAP_4_DIGIT_YEAR (1 << 0)

diff --git a/arch/sh/kernel/time.c b/arch/sh/kernel/time.c index fcd5e41977d1..eb0a91270499 100644 --- a/arch/sh/kernel/time.c +++ b/arch/sh/kernel/time.c @@ -22,75 +22,6 @@ #include <asm/clock.h> #include <asm/rtc.h>

-/* Dummy RTC ops */ -static void null_rtc_get_time(struct timespec *tv) -{ - tv->tv_sec = mktime(2000, 1, 1, 0, 0, 0); - tv->tv_nsec = 0; -} - -static int null_rtc_set_time(const time_t secs) -{ - return 0; -} - -void (*rtc_sh_get_time)(struct timespec *) = null_rtc_get_time; -int (*rtc_sh_set_time)(const time_t) = null_rtc_set_time; - -void read_persistent_clock(struct timespec *ts) -{ - rtc_sh_get_time(ts); -} - -#ifdef CONFIG_GENERIC_CMOS_UPDATE -int update_persistent_clock(struct timespec now) -{ - return rtc_sh_set_time(now.tv_sec); -} -#endif - -static int rtc_generic_get_time(struct device *dev, struct rtc_time *tm) -{ - struct timespec tv; - - rtc_sh_get_time(&tv); - rtc_time_to_tm(tv.tv_sec, tm); - return 0; -} - -static int rtc_generic_set_time(struct device *dev, struct rtc_time *tm) -{ - unsigned long secs; - - rtc_tm_to_time(tm, &secs); - if ((rtc_sh_set_time == null_rtc_set_time) || - (rtc_sh_set_time(secs) < 0)) - return -EOPNOTSUPP; - - return 0; -} - -static const struct rtc_class_ops rtc_generic_ops = { - .read_time = rtc_generic_get_time, - .set_time = rtc_generic_set_time, -}; - -static int __init rtc_generic_init(void) -{ - struct platform_device *pdev; - - if (rtc_sh_get_time == null_rtc_get_time) - return -ENODEV; - - pdev = platform_device_register_data(NULL, "rtc-generic", -1, - &rtc_generic_ops, - sizeof(rtc_generic_ops)); - - - return PTR_ERR_OR_ZERO(pdev); -} -device_initcall(rtc_generic_init); - void (*board_time_init)(void);

static void __init sh_late_time_init(void)

After arch/sh has removed the last reference to these functions, we can remove them completely and just rely on the 64-bit time_t based versions. This cleans up a rather ugly use of __weak functions.

Signed-off-by: Arnd Bergmann arnd@arndb.de --- include/linux/timekeeping32.h | 6 ------ kernel/time/ntp.c | 10 +--------- kernel/time/timekeeping.c | 12 ++---------- 3 files changed, 3 insertions(+), 25 deletions(-)

diff --git a/include/linux/timekeeping32.h b/include/linux/timekeeping32.h index a502616f7e1c..0036ff314ac5 100644 --- a/include/linux/timekeeping32.h +++ b/include/linux/timekeeping32.h @@ -52,10 +52,4 @@ static inline void getboottime(struct timespec *ts) *ts = timespec64_to_timespec(ts64); }

-/* - * Persistent clock related interfaces - */ -extern void read_persistent_clock(struct timespec *ts); -extern int update_persistent_clock(struct timespec now); - #endif diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c index c5e0cba3b39c..e23be418d015 100644 --- a/kernel/time/ntp.c +++ b/kernel/time/ntp.c @@ -555,17 +555,9 @@ static void sync_rtc_clock(void) }

#ifdef CONFIG_GENERIC_CMOS_UPDATE -int __weak update_persistent_clock(struct timespec now) -{ - return -ENODEV; -} - int __weak update_persistent_clock64(struct timespec64 now64) { - struct timespec now; - - now = timespec64_to_timespec(now64); - return update_persistent_clock(now); + return -ENODEV; } #endif

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 2d110c948805..eb09be4871b3 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -1467,7 +1467,7 @@ u64 timekeeping_max_deferment(void) }

/** - * read_persistent_clock - Return time from the persistent clock. + * read_persistent_clock64 - Return time from the persistent clock. * * Weak dummy function for arches that do not yet support it. * Reads the time from the battery backed persistent clock. @@ -1475,20 +1475,12 @@ u64 timekeeping_max_deferment(void) * * XXX - Do be sure to remove it once all arches implement it. */ -void __weak read_persistent_clock(struct timespec *ts) +void __weak read_persistent_clock64(struct timespec64 *ts) { ts->tv_sec = 0; ts->tv_nsec = 0; }

-void __weak read_persistent_clock64(struct timespec64 *ts64) -{ - struct timespec ts; - - read_persistent_clock(&ts); - *ts64 = timespec_to_timespec64(ts); -} - /** * read_persistent_wall_and_boot_offset - Read persistent clock, and also offset * from the boot.

current_time is the last remaining caller of current_kernel_time64(), which is a wrapper around ktime_get_coarse_real_ts64(). This calls the latter directly for consistency with the rest of the kernel that is moving to the ktime_get_ family of time accessors, as now documented in Documentation/core-api/timekeeping.rst.

An open questions is whether we may want to actually call the more accurate ktime_get_real_ts64() for file systems that save high-resolution timestamps in their on-disk format. This would add a small overhead to each update of the inode stamps but lead to inode timestamps to actually have a usable resolution better than one jiffy (1 to 10 milliseconds normally). Experiments on a variety of hardware platforms show a typical time of around 100 CPU cycles to read the cycle counter and calculate the accurate time from that. On old platforms without a cycle counter, this can be signiciantly higher, up to several microseconds to access a hardware clock, but those have become very rare by now.

I traced the original addition of the current_kernel_time() call to set the nanosecond fields back to linux-2.5.48, where Andi Kleen added a patch with subject "nanosecond stat timefields". Andi explains that the motivation was to introduce as little overhead as possible back then. At this time, reading the clock hardware was also more expensive when most architectures did not have a cycle counter.

One side effect of having more accurate inode timestamp would be having to write out the inode every time that mtime/ctime/atime get touched on most systems, whereas many file systems today only write it when the timestamps have changed, i.e. at most once per jiffy unless something else changes as well. That change would certainly be noticed in some workloads, which is enough reason to not do it without a good reason, regardless of the cost of reading the time.

One thing we could still consider however would be to round the timestamps from current_time() to multiples of NSEC_PER_JIFFY, e.g. full milliseconds rather than having six or seven meaningless but confusing digits at the end of the timestamp.

Link: http://lkml.kernel.org/r/20180726130820.4174359-1-arnd@arndb.de Signed-off-by: Arnd Bergmann arnd@arndb.de --- fs/inode.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/inode.c b/fs/inode.c index 9e198f00b64c..73432e64f874 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -2146,7 +2146,9 @@ EXPORT_SYMBOL(timespec64_trunc); */ struct timespec64 current_time(struct inode *inode) { - struct timespec64 now = current_kernel_time64(); + struct timespec64 now; + + ktime_get_coarse_real_ts64(&now);

if (unlikely(!inode->i_sb)) { WARN(1, "current_time() called with uninitialized super_block in the inode");