v4.19.13 snapshot.
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
new file mode 100644
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--- /dev/null
+++ b/include/linux/clocksource.h
@@ -0,0 +1,272 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* linux/include/linux/clocksource.h
+ *
+ * This file contains the structure definitions for clocksources.
+ *
+ * If you are not a clocksource, or timekeeping code, you should
+ * not be including this file!
+ */
+#ifndef _LINUX_CLOCKSOURCE_H
+#define _LINUX_CLOCKSOURCE_H
+
+#include <linux/types.h>
+#include <linux/timex.h>
+#include <linux/time.h>
+#include <linux/list.h>
+#include <linux/cache.h>
+#include <linux/timer.h>
+#include <linux/init.h>
+#include <linux/of.h>
+#include <asm/div64.h>
+#include <asm/io.h>
+
+struct clocksource;
+struct module;
+
+#ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
+#include <asm/clocksource.h>
+#endif
+
+/**
+ * struct clocksource - hardware abstraction for a free running counter
+ * Provides mostly state-free accessors to the underlying hardware.
+ * This is the structure used for system time.
+ *
+ * @name: ptr to clocksource name
+ * @list: list head for registration
+ * @rating: rating value for selection (higher is better)
+ * To avoid rating inflation the following
+ * list should give you a guide as to how
+ * to assign your clocksource a rating
+ * 1-99: Unfit for real use
+ * Only available for bootup and testing purposes.
+ * 100-199: Base level usability.
+ * Functional for real use, but not desired.
+ * 200-299: Good.
+ * A correct and usable clocksource.
+ * 300-399: Desired.
+ * A reasonably fast and accurate clocksource.
+ * 400-499: Perfect
+ * The ideal clocksource. A must-use where
+ * available.
+ * @read: returns a cycle value, passes clocksource as argument
+ * @enable: optional function to enable the clocksource
+ * @disable: optional function to disable the clocksource
+ * @mask: bitmask for two's complement
+ * subtraction of non 64 bit counters
+ * @mult: cycle to nanosecond multiplier
+ * @shift: cycle to nanosecond divisor (power of two)
+ * @max_idle_ns: max idle time permitted by the clocksource (nsecs)
+ * @maxadj: maximum adjustment value to mult (~11%)
+ * @max_cycles: maximum safe cycle value which won't overflow on multiplication
+ * @flags: flags describing special properties
+ * @archdata: arch-specific data
+ * @suspend: suspend function for the clocksource, if necessary
+ * @resume: resume function for the clocksource, if necessary
+ * @mark_unstable: Optional function to inform the clocksource driver that
+ * the watchdog marked the clocksource unstable
+ * @owner: module reference, must be set by clocksource in modules
+ *
+ * Note: This struct is not used in hotpathes of the timekeeping code
+ * because the timekeeper caches the hot path fields in its own data
+ * structure, so no line cache alignment is required,
+ *
+ * The pointer to the clocksource itself is handed to the read
+ * callback. If you need extra information there you can wrap struct
+ * clocksource into your own struct. Depending on the amount of
+ * information you need you should consider to cache line align that
+ * structure.
+ */
+struct clocksource {
+ u64 (*read)(struct clocksource *cs);
+ u64 mask;
+ u32 mult;
+ u32 shift;
+ u64 max_idle_ns;
+ u32 maxadj;
+#ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
+ struct arch_clocksource_data archdata;
+#endif
+ u64 max_cycles;
+ const char *name;
+ struct list_head list;
+ int rating;
+ int (*enable)(struct clocksource *cs);
+ void (*disable)(struct clocksource *cs);
+ unsigned long flags;
+ void (*suspend)(struct clocksource *cs);
+ void (*resume)(struct clocksource *cs);
+ void (*mark_unstable)(struct clocksource *cs);
+ void (*tick_stable)(struct clocksource *cs);
+
+ /* private: */
+#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
+ /* Watchdog related data, used by the framework */
+ struct list_head wd_list;
+ u64 cs_last;
+ u64 wd_last;
+#endif
+ struct module *owner;
+};
+
+/*
+ * Clock source flags bits::
+ */
+#define CLOCK_SOURCE_IS_CONTINUOUS 0x01
+#define CLOCK_SOURCE_MUST_VERIFY 0x02
+
+#define CLOCK_SOURCE_WATCHDOG 0x10
+#define CLOCK_SOURCE_VALID_FOR_HRES 0x20
+#define CLOCK_SOURCE_UNSTABLE 0x40
+#define CLOCK_SOURCE_SUSPEND_NONSTOP 0x80
+#define CLOCK_SOURCE_RESELECT 0x100
+
+/* simplify initialization of mask field */
+#define CLOCKSOURCE_MASK(bits) GENMASK_ULL((bits) - 1, 0)
+
+static inline u32 clocksource_freq2mult(u32 freq, u32 shift_constant, u64 from)
+{
+ /* freq = cyc/from
+ * mult/2^shift = ns/cyc
+ * mult = ns/cyc * 2^shift
+ * mult = from/freq * 2^shift
+ * mult = from * 2^shift / freq
+ * mult = (from<<shift) / freq
+ */
+ u64 tmp = ((u64)from) << shift_constant;
+
+ tmp += freq/2; /* round for do_div */
+ do_div(tmp, freq);
+
+ return (u32)tmp;
+}
+
+/**
+ * clocksource_khz2mult - calculates mult from khz and shift
+ * @khz: Clocksource frequency in KHz
+ * @shift_constant: Clocksource shift factor
+ *
+ * Helper functions that converts a khz counter frequency to a timsource
+ * multiplier, given the clocksource shift value
+ */
+static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
+{
+ return clocksource_freq2mult(khz, shift_constant, NSEC_PER_MSEC);
+}
+
+/**
+ * clocksource_hz2mult - calculates mult from hz and shift
+ * @hz: Clocksource frequency in Hz
+ * @shift_constant: Clocksource shift factor
+ *
+ * Helper functions that converts a hz counter
+ * frequency to a timsource multiplier, given the
+ * clocksource shift value
+ */
+static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
+{
+ return clocksource_freq2mult(hz, shift_constant, NSEC_PER_SEC);
+}
+
+/**
+ * clocksource_cyc2ns - converts clocksource cycles to nanoseconds
+ * @cycles: cycles
+ * @mult: cycle to nanosecond multiplier
+ * @shift: cycle to nanosecond divisor (power of two)
+ *
+ * Converts clocksource cycles to nanoseconds, using the given @mult and @shift.
+ * The code is optimized for performance and is not intended to work
+ * with absolute clocksource cycles (as those will easily overflow),
+ * but is only intended to be used with relative (delta) clocksource cycles.
+ *
+ * XXX - This could use some mult_lxl_ll() asm optimization
+ */
+static inline s64 clocksource_cyc2ns(u64 cycles, u32 mult, u32 shift)
+{
+ return ((u64) cycles * mult) >> shift;
+}
+
+
+extern int clocksource_unregister(struct clocksource*);
+extern void clocksource_touch_watchdog(void);
+extern void clocksource_change_rating(struct clocksource *cs, int rating);
+extern void clocksource_suspend(void);
+extern void clocksource_resume(void);
+extern struct clocksource * __init clocksource_default_clock(void);
+extern void clocksource_mark_unstable(struct clocksource *cs);
+extern void
+clocksource_start_suspend_timing(struct clocksource *cs, u64 start_cycles);
+extern u64 clocksource_stop_suspend_timing(struct clocksource *cs, u64 now);
+
+extern u64
+clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cycles);
+extern void
+clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
+
+/*
+ * Don't call __clocksource_register_scale directly, use
+ * clocksource_register_hz/khz
+ */
+extern int
+__clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
+extern void
+__clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq);
+
+/*
+ * Don't call this unless you are a default clocksource
+ * (AKA: jiffies) and absolutely have to.
+ */
+static inline int __clocksource_register(struct clocksource *cs)
+{
+ return __clocksource_register_scale(cs, 1, 0);
+}
+
+static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
+{
+ return __clocksource_register_scale(cs, 1, hz);
+}
+
+static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
+{
+ return __clocksource_register_scale(cs, 1000, khz);
+}
+
+static inline void __clocksource_update_freq_hz(struct clocksource *cs, u32 hz)
+{
+ __clocksource_update_freq_scale(cs, 1, hz);
+}
+
+static inline void __clocksource_update_freq_khz(struct clocksource *cs, u32 khz)
+{
+ __clocksource_update_freq_scale(cs, 1000, khz);
+}
+
+
+extern int timekeeping_notify(struct clocksource *clock);
+
+extern u64 clocksource_mmio_readl_up(struct clocksource *);
+extern u64 clocksource_mmio_readl_down(struct clocksource *);
+extern u64 clocksource_mmio_readw_up(struct clocksource *);
+extern u64 clocksource_mmio_readw_down(struct clocksource *);
+
+extern int clocksource_mmio_init(void __iomem *, const char *,
+ unsigned long, int, unsigned, u64 (*)(struct clocksource *));
+
+extern int clocksource_i8253_init(void);
+
+#define TIMER_OF_DECLARE(name, compat, fn) \
+ OF_DECLARE_1_RET(timer, name, compat, fn)
+
+#define CLOCKSOURCE_OF_DECLARE(name, compat, fn) \
+ TIMER_OF_DECLARE(name, compat, fn)
+
+#ifdef CONFIG_TIMER_PROBE
+extern void timer_probe(void);
+#else
+static inline void timer_probe(void) {}
+#endif
+
+#define TIMER_ACPI_DECLARE(name, table_id, fn) \
+ ACPI_DECLARE_PROBE_ENTRY(timer, name, table_id, 0, NULL, 0, fn)
+
+#endif /* _LINUX_CLOCKSOURCE_H */