/*
* Hardware Clocks
*
* Copyright GreenSocs 2016-2020
*
* Authors:
* Frederic Konrad
* Damien Hedde
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#ifndef QEMU_HW_CLOCK_H
#define QEMU_HW_CLOCK_H
#include "qom/object.h"
#include "qemu/queue.h"
#include "qemu/host-utils.h"
#include "qemu/bitops.h"
#define TYPE_CLOCK "clock"
OBJECT_DECLARE_SIMPLE_TYPE(Clock, CLOCK)
/*
* Argument to ClockCallback functions indicating why the callback
* has been called. A mask of these values logically ORed together
* is used to specify which events are interesting when the callback
* is registered, so these values must all be different bit values.
*/
typedef enum ClockEvent {
ClockUpdate = 1, /* Clock period has just updated */
ClockPreUpdate = 2, /* Clock period is about to update */
} ClockEvent;
typedef void ClockCallback(void *opaque, ClockEvent event);
/*
* clock store a value representing the clock's period in 2^-32ns unit.
* It can represent:
* + periods from 2^-32ns up to 4seconds
* + frequency from ~0.25Hz 2e10Ghz
* Resolution of frequency representation decreases with frequency:
* + at 100MHz, resolution is ~2mHz
* + at 1Ghz, resolution is ~0.2Hz
* + at 10Ghz, resolution is ~20Hz
*/
#define CLOCK_PERIOD_1SEC (1000000000llu << 32)
/*
* macro helpers to convert to hertz / nanosecond
*/
#define CLOCK_PERIOD_FROM_NS(ns) ((ns) * (CLOCK_PERIOD_1SEC / 1000000000llu))
#define CLOCK_PERIOD_FROM_HZ(hz) (((hz) != 0) ? CLOCK_PERIOD_1SEC / (hz) : 0u)
#define CLOCK_PERIOD_TO_HZ(per) (((per) != 0) ? CLOCK_PERIOD_1SEC / (per) : 0u)
/**
* Clock:
* @parent_obj: parent class
* @period: unsigned integer representing the period of the clock
* @canonical_path: clock path string cache (used for trace purpose)
* @callback: called when clock changes
* @callback_opaque: argument for @callback
* @callback_events: mask of events when callback should be called
* @source: source (or parent in clock tree) of the clock
* @children: list of clocks connected to this one (it is their source)
* @sibling: structure used to form a clock list
*/
struct Clock {
/*< private >*/
Object parent_obj;
/* all fields are private and should not be modified directly */
/* fields */
uint64_t period;
char *canonical_path;
ClockCallback *callback;
void *callback_opaque;
unsigned int callback_events;
/* Ratio of the parent clock to run the child clocks at */
uint32_t multiplier;
uint32_t divider;
/* Clocks are organized in a clock tree */
Clock *source;
QLIST_HEAD(, Clock) children;
QLIST_ENTRY(Clock) sibling;
};
/*
* vmstate description entry to be added in device vmsd.
*/
extern const VMStateDescription vmstate_clock;
#define VMSTATE_CLOCK(field, state) \
VMSTATE_CLOCK_V(field, state, 0)
#define VMSTATE_CLOCK_V(field, state, version) \
VMSTATE_STRUCT_POINTER_V(field, state, version, vmstate_clock, Clock)
#define VMSTATE_ARRAY_CLOCK(field, state, num) \
VMSTATE_ARRAY_CLOCK_V(field, state, num, 0)
#define VMSTATE_ARRAY_CLOCK_V(field, state, num, version) \
VMSTATE_ARRAY_OF_POINTER_TO_STRUCT(field, state, num, version, \
vmstate_clock, Clock)
/**
* clock_setup_canonical_path:
* @clk: clock
*
* compute the canonical path of the clock (used by log messages)
*/
void clock_setup_canonical_path(Clock *clk);
/**
* clock_new:
* @parent: the clock parent
* @name: the clock object name
*
* Helper function to create a new clock and parent it to @parent. There is no
* need to call clock_setup_canonical_path on the returned clock as it is done
* by this function.
*
* @return the newly created clock
*/
Clock *clock_new(Object *parent, const char *name);
/**
* clock_set_callback:
* @clk: the clock to register the callback into
* @cb: the callback function
* @opaque: the argument to the callback
* @events: the events the callback should be called for
* (logical OR of ClockEvent enum values)
*
* Register a callback called on every clock update.
* Note that a clock has only one callback: you cannot register
* different callback functions for different events.
*/
void clock_set_callback(Clock *clk, ClockCallback *cb,
void *opaque, unsigned int events);
/**
* clock_clear_callback:
* @clk: the clock to delete the callback from
*
* Unregister the callback registered with clock_set_callback.
*/
void clock_clear_callback(Clock *clk);
/**
* clock_set_source:
* @clk: the clock.
* @src: the source clock
*
* Setup @src as the clock source of @clk. The current @src period
* value is also copied to @clk and its subtree but no callback is
* called.
* Further @src update will be propagated to @clk and its subtree.
*/
void clock_set_source(Clock *clk, Clock *src);
/**
* clock_has_source:
* @clk: the clock
*
* Returns true if the clock has a source clock connected to it.
* This is useful for devices which have input clocks which must
* be connected by the board/SoC code which creates them. The
* device code can use this to check in its realize method that
* the clock has been connected.
*/
static inline bool clock_has_source(const Clock *clk)
{
return clk->source != NULL;
}
/**
* clock_set:
* @clk: the clock to initialize.
* @value: the clock's value, 0 means unclocked
*
* Set the local cached period value of @clk to @value.
*
* @return: true if the clock is changed.
*/
bool clock_set(Clock *clk, uint64_t value);
static inline bool clock_set_hz(Clock *clk, unsigned hz)
{
return clock_set(clk, CLOCK_PERIOD_FROM_HZ(hz));
}
static inline bool clock_set_ns(Clock *clk, unsigned ns)
{
return clock_set(clk, CLOCK_PERIOD_FROM_NS(ns));
}
/**
* clock_propagate:
* @clk: the clock
*
* Propagate the clock period that has been previously configured using
* @clock_set(). This will update recursively all connected clocks.
* It is an error to call this function on a clock which has a source.
* Note: this function must not be called during device inititialization
* or migration.
*/
void clock_propagate(Clock *clk);
/**
* clock_update:
* @clk: the clock to update.
* @value: the new clock's value, 0 means unclocked
*
* Update the @clk to the new @value. All connected clocks will be informed
* of this update. This is equivalent to call @clock_set() then
* @clock_propagate().
*/
static inline void clock_update(Clock *clk, uint64_t value)
{
if (clock_set(clk, value)) {
clock_propagate(clk);
}
}
static inline void clock_update_hz(Clock *clk, unsigned hz)
{
clock_update(clk, CLOCK_PERIOD_FROM_HZ(hz));
}
static inline void clock_update_ns(Clock *clk, unsigned ns)
{
clock_update(clk, CLOCK_PERIOD_FROM_NS(ns));
}
/**
* clock_get:
* @clk: the clk to fetch the clock
*
* @return: the current period.
*/
static inline uint64_t clock_get(const Clock *clk)
{
return clk->period;
}
static inline unsigned clock_get_hz(Clock *clk)
{
return CLOCK_PERIOD_TO_HZ(clock_get(clk));
}
/**
* clock_ticks_to_ns:
* @clk: the clock to query
* @ticks: number of ticks
*
* Returns the length of time in nanoseconds for this clock
* to tick @ticks times. Because a clock can have a period
* which is not a whole number of nanoseconds, it is important
* to use this function when calculating things like timer
* expiry deadlines, rather than attempting to obtain a "period
* in nanoseconds" value and then multiplying that by a number
* of ticks.
*
* The result could in theory be too large to fit in a 64-bit
* value if the number of ticks and the clock period are both
* large; to avoid overflow the result will be saturated to INT64_MAX
* (because this is the largest valid input to the QEMUTimer APIs).
* Since INT64_MAX nanoseconds is almost 300 years, anything with
* an expiry later than that is in the "will never happen" category
* and callers can reasonably not special-case the saturated result.
*/
static inline uint64_t clock_ticks_to_ns(const Clock *clk, uint64_t ticks)
{
uint64_t ns_low, ns_high;
/*
* clk->period is the period in units of 2^-32 ns, so
* (clk->period * ticks) is the required length of time in those
* units, and we can convert to nanoseconds by multiplying by
* 2^32, which is the same as shifting the 128-bit multiplication
* result right by 32.
*/
mulu64(&ns_low, &ns_high, clk->period, ticks);
if (ns_high & MAKE_64BIT_MASK(31, 33)) {
return INT64_MAX;
}
return ns_low >> 32 | ns_high << 32;
}
/**
* clock_ns_to_ticks:
* @clk: the clock to query
* @ns: duration in nanoseconds
*
* Returns the number of ticks this clock would make in the given
* number of nanoseconds. Because a clock can have a period which
* is not a whole number of nanoseconds, it is important to use this
* function rather than attempting to obtain a "period in nanoseconds"
* value and then dividing the duration by that value.
*
* If the clock is stopped (ie it has period zero), returns 0.
*
* For some inputs the result could overflow a 64-bit value (because
* the clock's period is short and the duration is long). In these
* cases we truncate the result to a 64-bit value. This is on the
* assumption that generally the result is going to be used to report
* a 32-bit or 64-bit guest register value, so wrapping either cannot
* happen or is the desired behaviour.
*/
static inline uint64_t clock_ns_to_ticks(const Clock *clk, uint64_t ns)
{
/*
* ticks = duration_in_ns / period_in_ns
* = ns / (period / 2^32)
* = (ns * 2^32) / period
* The hi, lo inputs to divu128() are (ns << 32) as a 128 bit value.
*/
uint64_t lo = ns << 32;
uint64_t hi = ns >> 32;
if (clk->period == 0) {
return 0;
}
divu128(&lo, &hi, clk->period);
return lo;
}
/**
* clock_is_enabled:
* @clk: a clock
*
* @return: true if the clock is running.
*/
static inline bool clock_is_enabled(const Clock *clk)
{
return clock_get(clk) != 0;
}
/**
* clock_display_freq: return human-readable representation of clock frequency
* @clk: clock
*
* Return a string which has a human-readable representation of the
* clock's frequency, e.g. "33.3 MHz". This is intended for debug
* and display purposes.
*
* The caller is responsible for freeing the string with g_free().
*/
char *clock_display_freq(Clock *clk);
/**
* clock_set_mul_div: set multiplier/divider for child clocks
* @clk: clock
* @multiplier: multiplier value
* @divider: divider value
*
* By default, a Clock's children will all run with the same period
* as their parent. This function allows you to adjust the multiplier
* and divider used to derive the child clock frequency.
* For example, setting a multiplier of 2 and a divider of 3
* will run child clocks with a period 2/3 of the parent clock,
* so if the parent clock is an 8MHz clock the children will
* be 12MHz.
*
* Setting the multiplier to 0 will stop the child clocks.
* Setting the divider to 0 is a programming error (diagnosed with
* an assertion failure).
* Setting a multiplier value that results in the child period
* overflowing is not diagnosed.
*
* Note that this function does not call clock_propagate(); the
* caller should do that if necessary.
*/
void clock_set_mul_div(Clock *clk, uint32_t multiplier, uint32_t divider);
#endif /* QEMU_HW_CLOCK_H */
