hw/core/clock: introduce clock object

This object may be used to represent a clock inside a clock tree.

A clock may be connected to another clock so that it receives update,
through a callback, whenever the source/parent clock is updated.

Although only the root clock of a clock tree controls the values
(represented as periods) of all clocks in tree, each clock holds
a local state containing the current value so that it can be fetched
independently. It will allows us to fullfill migration requirements
by migrating each clock independently of others.

This is based on the original work of Frederic Konrad.

Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Message-id: 20200406135251.157596-2-damien.hedde@greensocs.com
[PMM: Use uint64_t rather than unsigned long long in trace events;
 the dtrace backend can't handle the latter]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 216 insertions, 0 deletions

diff --git a/include/hw/clock.h b/include/hw/clock.h
new file mode 100644
index 0000000000..e0e19db9bd
--- /dev/null
+++ b/include/hw/clock.h
@@ -0,0 +1,216 @@
+/*
+ * 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"
+
+#define TYPE_CLOCK "clock"
+#define CLOCK(obj) OBJECT_CHECK(Clock, (obj), TYPE_CLOCK)
+
+typedef void ClockCallback(void *opaque);
+
+/*
+ * 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_TO_NS(per) ((per) / (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
+ * @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
+ */
+
+typedef struct Clock Clock;
+
+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;
+
+    /* Clocks are organized in a clock tree */
+    Clock *source;
+    QLIST_HEAD(, Clock) children;
+    QLIST_ENTRY(Clock) sibling;
+};
+
+/**
+ * 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_set_callback:
+ * @clk: the clock to register the callback into
+ * @cb: the callback function
+ * @opaque: the argument to the callback
+ *
+ * Register a callback called on every clock update.
+ */
+void clock_set_callback(Clock *clk, ClockCallback *cb, void *opaque);
+
+/**
+ * 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_set:
+ * @clk: the clock to initialize.
+ * @value: the clock's value, 0 means unclocked
+ *
+ * Set the local cached period value of @clk to @value.
+ */
+void clock_set(Clock *clk, uint64_t value);
+
+static inline void clock_set_hz(Clock *clk, unsigned hz)
+{
+    clock_set(clk, CLOCK_PERIOD_FROM_HZ(hz));
+}
+
+static inline void clock_set_ns(Clock *clk, unsigned ns)
+{
+    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)
+{
+    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));
+}
+
+static inline unsigned clock_get_ns(Clock *clk)
+{
+    return CLOCK_PERIOD_TO_NS(clock_get(clk));
+}
+
+/**
+ * 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;
+}
+
+static inline void clock_init(Clock *clk, uint64_t value)
+{
+    clock_set(clk, value);
+}
+static inline void clock_init_hz(Clock *clk, uint64_t value)
+{
+    clock_set_hz(clk, value);
+}
+static inline void clock_init_ns(Clock *clk, uint64_t value)
+{
+    clock_set_ns(clk, value);
+}
+
+#endif /* QEMU_HW_CLOCK_H */