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