include/linux/clocksource.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*  linux/include/linux/clocksource.h
   3  *
   4  *  This file contains the structure definitions for clocksources.
   5  *
   6  *  If you are not a clocksource, or timekeeping code, you should
   7  *  not be including this file!
   8  */
   9 #ifndef _LINUX_CLOCKSOURCE_H
  10 #define _LINUX_CLOCKSOURCE_H
  11
  12 #include <linux/types.h>
  13 #include <linux/timex.h>
  14 #include <linux/time.h>
  15 #include <linux/list.h>
  16 #include <linux/cache.h>
  17 #include <linux/timer.h>
  18 #include <linux/init.h>
  19 #include <linux/of.h>
  20 #include <linux/clocksource_ids.h>
  21 #include <asm/div64.h>
  22 #include <asm/io.h>
  23
  24 struct clocksource;
  25 struct module;
  26
  27 #if defined(CONFIG_ARCH_CLOCKSOURCE_DATA) || \
  28     defined(CONFIG_GENERIC_GETTIMEOFDAY)
  29 #include <asm/clocksource.h>
  30 #endif
  31
  32 #include <vdso/clocksource.h>
  33
  34 /**
  35  * struct clocksource - hardware abstraction for a free running counter
  36  *      Provides mostly state-free accessors to the underlying hardware.
  37  *      This is the structure used for system time.
  38  *
  39  * @read:               Returns a cycle value, passes clocksource as argument
  40  * @mask:               Bitmask for two's complement
  41  *                      subtraction of non 64 bit counters
  42  * @mult:               Cycle to nanosecond multiplier
  43  * @shift:              Cycle to nanosecond divisor (power of two)
  44  * @max_idle_ns:        Maximum idle time permitted by the clocksource (nsecs)
  45  * @maxadj:             Maximum adjustment value to mult (~11%)
  46  * @archdata:           Optional arch-specific data
  47  * @max_cycles:         Maximum safe cycle value which won't overflow on
  48  *                      multiplication
  49  * @name:               Pointer to clocksource name
  50  * @list:               List head for registration (internal)
  51  * @rating:             Rating value for selection (higher is better)
  52  *                      To avoid rating inflation the following
  53  *                      list should give you a guide as to how
  54  *                      to assign your clocksource a rating
  55  *                      1-99: Unfit for real use
  56  *                              Only available for bootup and testing purposes.
  57  *                      100-199: Base level usability.
  58  *                              Functional for real use, but not desired.
  59  *                      200-299: Good.
  60  *                              A correct and usable clocksource.
  61  *                      300-399: Desired.
  62  *                              A reasonably fast and accurate clocksource.
  63  *                      400-499: Perfect
  64  *                              The ideal clocksource. A must-use where
  65  *                              available.
  66  * @id:                 Defaults to CSID_GENERIC. The id value is captured
  67  *                      in certain snapshot functions to allow callers to
  68  *                      validate the clocksource from which the snapshot was
  69  *                      taken.
  70  * @flags:              Flags describing special properties
  71  * @enable:             Optional function to enable the clocksource
  72  * @disable:            Optional function to disable the clocksource
  73  * @suspend:            Optional suspend function for the clocksource
  74  * @resume:             Optional resume function for the clocksource
  75  * @mark_unstable:      Optional function to inform the clocksource driver that
  76  *                      the watchdog marked the clocksource unstable
  77  * @tick_stable:        Optional function called periodically from the watchdog
  78  *                      code to provide stable synchronization points
  79  * @wd_list:            List head to enqueue into the watchdog list (internal)
  80  * @cs_last:            Last clocksource value for clocksource watchdog
  81  * @wd_last:            Last watchdog value corresponding to @cs_last
  82  * @owner:              Module reference, must be set by clocksource in modules
  83  *
  84  * Note: This struct is not used in hotpathes of the timekeeping code
  85  * because the timekeeper caches the hot path fields in its own data
  86  * structure, so no cache line alignment is required,
  87  *
  88  * The pointer to the clocksource itself is handed to the read
  89  * callback. If you need extra information there you can wrap struct
  90  * clocksource into your own struct. Depending on the amount of
  91  * information you need you should consider to cache line align that
  92  * structure.
  93  */
  94 struct clocksource {
  95         u64                     (*read)(struct clocksource *cs);
  96         u64                     mask;
  97         u32                     mult;
  98         u32                     shift;
  99         u64                     max_idle_ns;
 100         u32                     maxadj;
 101 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
 102         struct arch_clocksource_data archdata;
 103 #endif
 104         u64                     max_cycles;
 105         const char              *name;
 106         struct list_head        list;
 107         int                     rating;
 108         enum clocksource_ids    id;
 109         enum vdso_clock_mode    vdso_clock_mode;
 110         unsigned long           flags;
 111
 112         int                     (*enable)(struct clocksource *cs);
 113         void                    (*disable)(struct clocksource *cs);
 114         void                    (*suspend)(struct clocksource *cs);
 115         void                    (*resume)(struct clocksource *cs);
 116         void                    (*mark_unstable)(struct clocksource *cs);
 117         void                    (*tick_stable)(struct clocksource *cs);
 118
 119         /* private: */
 120 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
 121         /* Watchdog related data, used by the framework */
 122         struct list_head        wd_list;
 123         u64                     cs_last;
 124         u64                     wd_last;
 125 #endif
 126         struct module           *owner;
 127 };
 128
 129 /*
 130  * Clock source flags bits::
 131  */
 132 #define CLOCK_SOURCE_IS_CONTINUOUS              0x01
 133 #define CLOCK_SOURCE_MUST_VERIFY                0x02
 134
 135 #define CLOCK_SOURCE_WATCHDOG                   0x10
 136 #define CLOCK_SOURCE_VALID_FOR_HRES             0x20
 137 #define CLOCK_SOURCE_UNSTABLE                   0x40
 138 #define CLOCK_SOURCE_SUSPEND_NONSTOP            0x80
 139 #define CLOCK_SOURCE_RESELECT                   0x100
 140
 141 /* simplify initialization of mask field */
 142 #define CLOCKSOURCE_MASK(bits) GENMASK_ULL((bits) - 1, 0)
 143
 144 static inline u32 clocksource_freq2mult(u32 freq, u32 shift_constant, u64 from)
 145 {
 146         /*  freq = cyc/from
 147          *  mult/2^shift  = ns/cyc
 148          *  mult = ns/cyc * 2^shift
 149          *  mult = from/freq * 2^shift
 150          *  mult = from * 2^shift / freq
 151          *  mult = (from<<shift) / freq
 152          */
 153         u64 tmp = ((u64)from) << shift_constant;
 154
 155         tmp += freq/2; /* round for do_div */
 156         do_div(tmp, freq);
 157
 158         return (u32)tmp;
 159 }
 160
 161 /**
 162  * clocksource_khz2mult - calculates mult from khz and shift
 163  * @khz:                Clocksource frequency in KHz
 164  * @shift_constant:     Clocksource shift factor
 165  *
 166  * Helper functions that converts a khz counter frequency to a timsource
 167  * multiplier, given the clocksource shift value
 168  */
 169 static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
 170 {
 171         return clocksource_freq2mult(khz, shift_constant, NSEC_PER_MSEC);
 172 }
 173
 174 /**
 175  * clocksource_hz2mult - calculates mult from hz and shift
 176  * @hz:                 Clocksource frequency in Hz
 177  * @shift_constant:     Clocksource shift factor
 178  *
 179  * Helper functions that converts a hz counter
 180  * frequency to a timsource multiplier, given the
 181  * clocksource shift value
 182  */
 183 static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
 184 {
 185         return clocksource_freq2mult(hz, shift_constant, NSEC_PER_SEC);
 186 }
 187
 188 /**
 189  * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
 190  * @cycles:     cycles
 191  * @mult:       cycle to nanosecond multiplier
 192  * @shift:      cycle to nanosecond divisor (power of two)
 193  *
 194  * Converts clocksource cycles to nanoseconds, using the given @mult and @shift.
 195  * The code is optimized for performance and is not intended to work
 196  * with absolute clocksource cycles (as those will easily overflow),
 197  * but is only intended to be used with relative (delta) clocksource cycles.
 198  *
 199  * XXX - This could use some mult_lxl_ll() asm optimization
 200  */
 201 static inline s64 clocksource_cyc2ns(u64 cycles, u32 mult, u32 shift)
 202 {
 203         return ((u64) cycles * mult) >> shift;
 204 }
 205
 206
 207 extern int clocksource_unregister(struct clocksource*);
 208 extern void clocksource_touch_watchdog(void);
 209 extern void clocksource_change_rating(struct clocksource *cs, int rating);
 210 extern void clocksource_suspend(void);
 211 extern void clocksource_resume(void);
 212 extern struct clocksource * __init clocksource_default_clock(void);
 213 extern void clocksource_mark_unstable(struct clocksource *cs);
 214 extern void
 215 clocksource_start_suspend_timing(struct clocksource *cs, u64 start_cycles);
 216 extern u64 clocksource_stop_suspend_timing(struct clocksource *cs, u64 now);
 217
 218 extern u64
 219 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles);
 220 extern void
 221 clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
 222
 223 /*
 224  * Don't call __clocksource_register_scale directly, use
 225  * clocksource_register_hz/khz
 226  */
 227 extern int
 228 __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
 229 extern void
 230 __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq);
 231
 232 /*
 233  * Don't call this unless you are a default clocksource
 234  * (AKA: jiffies) and absolutely have to.
 235  */
 236 static inline int __clocksource_register(struct clocksource *cs)
 237 {
 238         return __clocksource_register_scale(cs, 1, 0);
 239 }
 240
 241 static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
 242 {
 243         return __clocksource_register_scale(cs, 1, hz);
 244 }
 245
 246 static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
 247 {
 248         return __clocksource_register_scale(cs, 1000, khz);
 249 }
 250
 251 static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz)
 252 {
 253         __clocksource_update_freq_scale(cs, 1, hz);
 254 }
 255
 256 static inline void __clocksource_update_freq_khz(struct clocksource *cs, u32 khz)
 257 {
 258         __clocksource_update_freq_scale(cs, 1000, khz);
 259 }
 260
 261 #ifdef CONFIG_ARCH_CLOCKSOURCE_INIT
 262 extern void clocksource_arch_init(struct clocksource *cs);
 263 #else
 264 static inline void clocksource_arch_init(struct clocksource *cs) { }
 265 #endif
 266
 267 extern int timekeeping_notify(struct clocksource *clock);
 268
 269 extern u64 clocksource_mmio_readl_up(struct clocksource *);
 270 extern u64 clocksource_mmio_readl_down(struct clocksource *);
 271 extern u64 clocksource_mmio_readw_up(struct clocksource *);
 272 extern u64 clocksource_mmio_readw_down(struct clocksource *);
 273
 274 extern int clocksource_mmio_init(void __iomem *, const char *,
 275         unsigned long, int, unsigned, u64 (*)(struct clocksource *));
 276
 277 extern int clocksource_i8253_init(void);
 278
 279 #define TIMER_OF_DECLARE(name, compat, fn) \
 280         OF_DECLARE_1_RET(timer, name, compat, fn)
 281
 282 #ifdef CONFIG_TIMER_PROBE
 283 extern void timer_probe(void);
 284 #else
 285 static inline void timer_probe(void) {}
 286 #endif
 287
 288 #define TIMER_ACPI_DECLARE(name, table_id, fn)          \
 289         ACPI_DECLARE_PROBE_ENTRY(timer, name, table_id, 0, NULL, 0, fn)
 290
 291 #endif /* _LINUX_CLOCKSOURCE_H */