Introduce clock port objects: ClockIn and ClockOut.

Theses ports may be used to distribute a clock from a object to several
other objects. The ClockIn object contains the current state of the
clock: the frequency.

A ClockIn may be connected to a ClockOut so that it receives update,
through the callback, whenever the Clockout is updated using the
ClockOut's set function.

This is based on the original work of Frederic Konrad.

Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
---
 Makefile.objs           |   1 +
 include/hw/clock-port.h | 136 ++++++++++++++++++++++++++++++++++
 hw/core/clock-port.c    | 159 ++++++++++++++++++++++++++++++++++++++++
 hw/core/Makefile.objs   |   1 +
 hw/core/trace-events    |   7 ++
 5 files changed, 304 insertions(+)
 create mode 100644 include/hw/clock-port.h
 create mode 100644 hw/core/clock-port.c
 create mode 100644 hw/core/trace-events

diff --git a/Makefile.objs b/Makefile.objs
index ce9c79235e..b29747075f 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -210,6 +210,7 @@ trace-events-subdirs += hw/audio
 trace-events-subdirs += hw/block
 trace-events-subdirs += hw/block/dataplane
 trace-events-subdirs += hw/char
+trace-events-subdirs += hw/core
 trace-events-subdirs += hw/display
 trace-events-subdirs += hw/dma
 trace-events-subdirs += hw/hppa
diff --git a/include/hw/clock-port.h b/include/hw/clock-port.h
new file mode 100644
index 0000000000..8266549350
--- /dev/null
+++ b/include/hw/clock-port.h
@@ -0,0 +1,136 @@
+#ifndef CLOCK_PORT_H
+#define CLOCK_PORT_H
+
+#include "qom/object.h"
+#include "hw/qdev-core.h"
+#include "qemu/queue.h"
+#include "migration/vmstate.h"
+
+#define TYPE_CLOCK_IN "clock-in"
+#define CLOCK_IN(obj) OBJECT_CHECK(ClockIn, (obj), TYPE_CLOCK_IN)
+#define TYPE_CLOCK_OUT "clock-out"
+#define CLOCK_OUT(obj) OBJECT_CHECK(ClockOut, (obj), TYPE_CLOCK_OUT)
+
+typedef void ClockCallback(void *opaque);
+
+typedef struct ClockOut ClockOut;
+typedef struct ClockIn ClockIn;
+
+struct ClockIn {
+    /*< private >*/
+    Object parent_obj;
+    /*< private >*/
+    uint64_t frequency;
+    char *canonical_path; /* clock path cache */
+    ClockOut *driver; /* clock output controlling this clock */
+    ClockCallback *callback; /* local callback */
+    void *callback_opaque; /* opaque argument for the callback */
+    QLIST_ENTRY(ClockIn) sibling;  /* entry in a followers list */
+};
+
+struct ClockOut {
+    /*< private >*/
+    Object parent_obj;
+    /*< private >*/
+    char *canonical_path; /* clock path cache */
+    QLIST_HEAD(, ClockIn) followers; /* list of registered clocks */
+};
+
+extern const VMStateDescription vmstate_clockin;
+
+/*
+ * vmstate description entry to be added in device vmsd.
+ */
+#define VMSTATE_CLOCKIN(_field, _state) \
+    VMSTATE_CLOCKIN_V(_field, _state, 0)
+#define VMSTATE_CLOCKIN_V(_field, _state, _version) \
+    VMSTATE_STRUCT_POINTER_V(_field, _state, _version, vmstate_clockin, ClockIn)
+
+/**
+ * clock_out_setup_canonical_path:
+ * @clk: clock
+ *
+ * compute the canonical path of the clock (used by log messages)
+ */
+void clock_out_setup_canonical_path(ClockOut *clk);
+
+/**
+ * clock_in_setup_canonical_path:
+ * @clk: clock
+ *
+ * compute the canonical path of the clock (used by log messages)
+ */
+void clock_in_setup_canonical_path(ClockIn *clk);
+
+/**
+ * clock_add_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(ClockIn *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(ClockIn *clk);
+
+/**
+ * clock_init_frequency:
+ * @clk: the clock to initialize.
+ * @freq: the clock's frequency in Hz or 0 if unclocked.
+ *
+ * Initialize the local cached frequency value of @clk to @freq.
+ * Note: this function must only be called during device inititialization
+ * or migration.
+ */
+void clock_init_frequency(ClockIn *clk, uint64_t freq);
+
+/**
+ * clock_connect:
+ * @clkin: the drived clock.
+ * @clkout: the driving clock.
+ *
+ * Setup @clkout to drive @clkin: Any @clkout update will be propagated
+ * to @clkin.
+ */
+void clock_connect(ClockIn *clkin, ClockOut *clkout);
+
+/**
+ * clock_set_frequency:
+ * @clk: the clock to update.
+ * @freq: the new clock's frequency in Hz or 0 if unclocked.
+ *
+ * Update the @clk to the new @freq.
+ * This change will be propagated through registered clock inputs.
+ */
+void clock_set_frequency(ClockOut *clk, uint64_t freq);
+
+/**
+ * clock_get_frequency:
+ * @clk: the clk to fetch the clock
+ *
+ * @return: the current frequency of @clk in Hz. If @clk is NULL, return 0.
+ */
+static inline uint64_t clock_get_frequency(const ClockIn *clk)
+{
+    return clk ? clk->frequency : 0;
+}
+
+/**
+ * clock_is_enabled:
+ * @clk: a clock state
+ *
+ * @return: true if the clock is running. If @clk is NULL return false.
+ */
+static inline bool clock_is_enabled(const ClockIn *clk)
+{
+    return clock_get_frequency(clk) != 0;
+}
+
+#endif /* CLOCK_PORT_H */
diff --git a/hw/core/clock-port.c b/hw/core/clock-port.c
new file mode 100644
index 0000000000..25bab0fbed
--- /dev/null
+++ b/hw/core/clock-port.c
@@ -0,0 +1,159 @@
+/*
+ * Clock inputs and outputs
+ *
+ * Copyright GreenSocs 2016-2018
+ *
+ * Authors:
+ *  Frederic Konrad <fred.konrad@greensocs.com>
+ *  Damien Hedde <damien.hedde@greensocs.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/module.h"
+#include "hw/clock-port.h"
+#include "hw/qdev-core.h"
+#include "migration/vmstate.h"
+#include "qemu/log.h"
+#include "qapi/error.h"
+#include "trace.h"
+
+const VMStateDescription vmstate_clockin = {
+    .name = "clockin",
+    .version_id = 0,
+    .minimum_version_id = 0,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT64(frequency, ClockIn),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+#define CLOCK_PATH(_clk) (_clk->canonical_path)
+
+void clock_out_setup_canonical_path(ClockOut *clk)
+{
+    g_free(clk->canonical_path);
+    clk->canonical_path = object_get_canonical_path(OBJECT(clk));
+}
+
+void clock_in_setup_canonical_path(ClockIn *clk)
+{
+    g_free(clk->canonical_path);
+    clk->canonical_path = object_get_canonical_path(OBJECT(clk));
+}
+
+void clock_set_callback(ClockIn *clk, ClockCallback *cb, void *opaque)
+{
+    assert(clk);
+
+    clk->callback = cb;
+    clk->callback_opaque = opaque;
+}
+
+void clock_init_frequency(ClockIn *clk, uint64_t freq)
+{
+    assert(clk);
+
+    clk->frequency = freq;
+}
+
+void clock_clear_callback(ClockIn *clk)
+{
+    clock_set_callback(clk, NULL, NULL);
+}
+
+void clock_connect(ClockIn *clkin, ClockOut *clkout)
+{
+    assert(clkin && clkin->driver == NULL);
+    assert(clkout);
+
+    trace_clock_connect(CLOCK_PATH(clkin), CLOCK_PATH(clkout));
+
+    QLIST_INSERT_HEAD(&clkout->followers, clkin, sibling);
+    clkin->driver = clkout;
+}
+
+static void clock_disconnect(ClockIn *clk)
+{
+    if (clk->driver == NULL) {
+        return;
+    }
+
+    trace_clock_disconnect(CLOCK_PATH(clk));
+
+    clk->driver = NULL;
+    QLIST_REMOVE(clk, sibling);
+}
+
+void clock_set_frequency(ClockOut *clk, uint64_t freq)
+{
+    ClockIn *follower;
+    trace_clock_update(CLOCK_PATH(clk), freq);
+
+    QLIST_FOREACH(follower, &clk->followers, sibling) {
+        trace_clock_propagate(CLOCK_PATH(clk), CLOCK_PATH(follower));
+        if (follower->frequency != freq) {
+            follower->frequency = freq;
+            if (follower->callback) {
+                follower->callback(follower->callback_opaque);
+            }
+        }
+    }
+}
+
+static void clock_out_initfn(Object *obj)
+{
+    ClockOut *clk = CLOCK_OUT(obj);
+
+    QLIST_INIT(&clk->followers);
+}
+
+static void clock_out_finalizefn(Object *obj)
+{
+    ClockOut *clk = CLOCK_OUT(obj);
+    ClockIn *follower, *next;
+
+    /* clear our list of followers */
+    QLIST_FOREACH_SAFE(follower, &clk->followers, sibling, next) {
+        clock_disconnect(follower);
+    }
+
+    g_free(clk->canonical_path);
+    clk->canonical_path = NULL;
+}
+
+static void clock_in_finalizefn(Object *obj)
+{
+    ClockIn *clk = CLOCK_IN(obj);
+
+    /* remove us from driver's followers list */
+    clock_disconnect(clk);
+
+    g_free(clk->canonical_path);
+    clk->canonical_path = NULL;
+}
+
+static const TypeInfo clock_out_info = {
+    .name              = TYPE_CLOCK_OUT,
+    .parent            = TYPE_OBJECT,
+    .instance_size     = sizeof(ClockOut),
+    .instance_init     = clock_out_initfn,
+    .instance_finalize = clock_out_finalizefn,
+};
+
+static const TypeInfo clock_in_info = {
+    .name              = TYPE_CLOCK_IN,
+    .parent            = TYPE_OBJECT,
+    .instance_size     = sizeof(ClockIn),
+    .instance_finalize = clock_in_finalizefn,
+};
+
+static void clock_register_types(void)
+{
+    type_register_static(&clock_in_info);
+    type_register_static(&clock_out_info);
+}
+
+type_init(clock_register_types)
diff --git a/hw/core/Makefile.objs b/hw/core/Makefile.objs
index eb88ca979e..f7102121f4 100644
--- a/hw/core/Makefile.objs
+++ b/hw/core/Makefile.objs
@@ -6,6 +6,7 @@ common-obj-$(CONFIG_SOFTMMU) += fw-path-provider.o
 # irq.o needed for qdev GPIO handling:
 common-obj-y += irq.o
 common-obj-y += hotplug.o
+common-obj-y += clock-port.o
 common-obj-$(CONFIG_SOFTMMU) += nmi.o
 
 common-obj-$(CONFIG_EMPTY_SLOT) += empty_slot.o
diff --git a/hw/core/trace-events b/hw/core/trace-events
new file mode 100644
index 0000000000..d4880ec138
--- /dev/null
+++ b/hw/core/trace-events
@@ -0,0 +1,7 @@
+# See docs/devel/tracing.txt for syntax documentation.
+
+# hw/core/clock-port.c
+clock_connect(const char *clk, const char *driver) "'%s' drived-by '%s'"
+clock_disconnect(const char *clk) "'%s'"
+clock_update(const char *clk, uint64_t freq) "'%s' frequency %" PRIu64 "Hz"
+clock_propagate(const char *clko, const char *clki) "'%s' => '%s'"
-- 
2.19.0

On 10/2/18 4:24 PM, Damien Hedde wrote:
> Introduce clock port objects: ClockIn and ClockOut.
> 
> Theses ports may be used to distribute a clock from a object to several
> other objects. The ClockIn object contains the current state of the
> clock: the frequency.
> 
> A ClockIn may be connected to a ClockOut so that it receives update,
> through the callback, whenever the Clockout is updated using the
> ClockOut's set function.
> 
> This is based on the original work of Frederic Konrad.
> 
> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
> ---
>  Makefile.objs           |   1 +
>  include/hw/clock-port.h | 136 ++++++++++++++++++++++++++++++++++
>  hw/core/clock-port.c    | 159 ++++++++++++++++++++++++++++++++++++++++
>  hw/core/Makefile.objs   |   1 +
>  hw/core/trace-events    |   7 ++
>  5 files changed, 304 insertions(+)
>  create mode 100644 include/hw/clock-port.h
>  create mode 100644 hw/core/clock-port.c
>  create mode 100644 hw/core/trace-events
> 
> diff --git a/Makefile.objs b/Makefile.objs
> index ce9c79235e..b29747075f 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -210,6 +210,7 @@ trace-events-subdirs += hw/audio
>  trace-events-subdirs += hw/block
>  trace-events-subdirs += hw/block/dataplane
>  trace-events-subdirs += hw/char
> +trace-events-subdirs += hw/core
>  trace-events-subdirs += hw/display
>  trace-events-subdirs += hw/dma
>  trace-events-subdirs += hw/hppa
> diff --git a/include/hw/clock-port.h b/include/hw/clock-port.h
> new file mode 100644
> index 0000000000..8266549350
> --- /dev/null
> +++ b/include/hw/clock-port.h
> @@ -0,0 +1,136 @@
> +#ifndef CLOCK_PORT_H
> +#define CLOCK_PORT_H
> +
> +#include "qom/object.h"
> +#include "hw/qdev-core.h"
> +#include "qemu/queue.h"
> +#include "migration/vmstate.h"
> +
> +#define TYPE_CLOCK_IN "clock-in"
> +#define CLOCK_IN(obj) OBJECT_CHECK(ClockIn, (obj), TYPE_CLOCK_IN)
> +#define TYPE_CLOCK_OUT "clock-out"
> +#define CLOCK_OUT(obj) OBJECT_CHECK(ClockOut, (obj), TYPE_CLOCK_OUT)
> +
> +typedef void ClockCallback(void *opaque);
> +
> +typedef struct ClockOut ClockOut;
> +typedef struct ClockIn ClockIn;
> +
> +struct ClockIn {
> +    /*< private >*/
> +    Object parent_obj;
> +    /*< private >*/
> +    uint64_t frequency;
> +    char *canonical_path; /* clock path cache */
> +    ClockOut *driver; /* clock output controlling this clock */
> +    ClockCallback *callback; /* local callback */
> +    void *callback_opaque; /* opaque argument for the callback */
> +    QLIST_ENTRY(ClockIn) sibling;  /* entry in a followers list */
> +};
> +
> +struct ClockOut {
> +    /*< private >*/
> +    Object parent_obj;
> +    /*< private >*/
> +    char *canonical_path; /* clock path cache */
> +    QLIST_HEAD(, ClockIn) followers; /* list of registered clocks */
> +};
> +
> +extern const VMStateDescription vmstate_clockin;
> +
> +/*
> + * vmstate description entry to be added in device vmsd.
> + */
> +#define VMSTATE_CLOCKIN(_field, _state) \
> +    VMSTATE_CLOCKIN_V(_field, _state, 0)
> +#define VMSTATE_CLOCKIN_V(_field, _state, _version) \
> +    VMSTATE_STRUCT_POINTER_V(_field, _state, _version, vmstate_clockin, ClockIn)
> +
> +/**
> + * clock_out_setup_canonical_path:
> + * @clk: clock
> + *
> + * compute the canonical path of the clock (used by log messages)
> + */
> +void clock_out_setup_canonical_path(ClockOut *clk);
> +
> +/**
> + * clock_in_setup_canonical_path:
> + * @clk: clock
> + *
> + * compute the canonical path of the clock (used by log messages)
> + */
> +void clock_in_setup_canonical_path(ClockIn *clk);
> +
> +/**
> + * clock_add_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(ClockIn *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(ClockIn *clk);
> +
> +/**
> + * clock_init_frequency:
> + * @clk: the clock to initialize.
> + * @freq: the clock's frequency in Hz or 0 if unclocked.
> + *
> + * Initialize the local cached frequency value of @clk to @freq.
> + * Note: this function must only be called during device inititialization
> + * or migration.
> + */
> +void clock_init_frequency(ClockIn *clk, uint64_t freq);
> +
> +/**
> + * clock_connect:
> + * @clkin: the drived clock.
> + * @clkout: the driving clock.
> + *
> + * Setup @clkout to drive @clkin: Any @clkout update will be propagated
> + * to @clkin.
> + */
> +void clock_connect(ClockIn *clkin, ClockOut *clkout);
> +
> +/**
> + * clock_set_frequency:
> + * @clk: the clock to update.
> + * @freq: the new clock's frequency in Hz or 0 if unclocked.
> + *
> + * Update the @clk to the new @freq.
> + * This change will be propagated through registered clock inputs.
> + */
> +void clock_set_frequency(ClockOut *clk, uint64_t freq);
> +
> +/**
> + * clock_get_frequency:
> + * @clk: the clk to fetch the clock
> + *
> + * @return: the current frequency of @clk in Hz. If @clk is NULL, return 0.
> + */
> +static inline uint64_t clock_get_frequency(const ClockIn *clk)
> +{
> +    return clk ? clk->frequency : 0;
> +}
> +
> +/**
> + * clock_is_enabled:
> + * @clk: a clock state
> + *
> + * @return: true if the clock is running. If @clk is NULL return false.
> + */
> +static inline bool clock_is_enabled(const ClockIn *clk)
> +{
> +    return clock_get_frequency(clk) != 0;
> +}
> +
> +#endif /* CLOCK_PORT_H */
> diff --git a/hw/core/clock-port.c b/hw/core/clock-port.c
> new file mode 100644
> index 0000000000..25bab0fbed
> --- /dev/null
> +++ b/hw/core/clock-port.c
> @@ -0,0 +1,159 @@
> +/*
> + * Clock inputs and outputs
> + *
> + * Copyright GreenSocs 2016-2018
> + *
> + * Authors:
> + *  Frederic Konrad <fred.konrad@greensocs.com>
> + *  Damien Hedde <damien.hedde@greensocs.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu/module.h"
> +#include "hw/clock-port.h"
> +#include "hw/qdev-core.h"
> +#include "migration/vmstate.h"
> +#include "qemu/log.h"
> +#include "qapi/error.h"
> +#include "trace.h"
> +
> +const VMStateDescription vmstate_clockin = {
> +    .name = "clockin",
> +    .version_id = 0,
> +    .minimum_version_id = 0,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_UINT64(frequency, ClockIn),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
> +#define CLOCK_PATH(_clk) (_clk->canonical_path)
> +
> +void clock_out_setup_canonical_path(ClockOut *clk)
> +{
> +    g_free(clk->canonical_path);
> +    clk->canonical_path = object_get_canonical_path(OBJECT(clk));
> +}
> +
> +void clock_in_setup_canonical_path(ClockIn *clk)
> +{
> +    g_free(clk->canonical_path);
> +    clk->canonical_path = object_get_canonical_path(OBJECT(clk));
> +}
> +
> +void clock_set_callback(ClockIn *clk, ClockCallback *cb, void *opaque)
> +{
> +    assert(clk);
> +
> +    clk->callback = cb;
> +    clk->callback_opaque = opaque;
> +}
> +
> +void clock_init_frequency(ClockIn *clk, uint64_t freq)
> +{
> +    assert(clk);
> +
> +    clk->frequency = freq;
> +}
> +
> +void clock_clear_callback(ClockIn *clk)
> +{
> +    clock_set_callback(clk, NULL, NULL);
> +}
> +
> +void clock_connect(ClockIn *clkin, ClockOut *clkout)
> +{
> +    assert(clkin && clkin->driver == NULL);
> +    assert(clkout);
> +
> +    trace_clock_connect(CLOCK_PATH(clkin), CLOCK_PATH(clkout));
> +
> +    QLIST_INSERT_HEAD(&clkout->followers, clkin, sibling);
> +    clkin->driver = clkout;
> +}
> +
> +static void clock_disconnect(ClockIn *clk)
> +{
> +    if (clk->driver == NULL) {
> +        return;
> +    }
> +
> +    trace_clock_disconnect(CLOCK_PATH(clk));
> +
> +    clk->driver = NULL;
> +    QLIST_REMOVE(clk, sibling);
> +}
> +
> +void clock_set_frequency(ClockOut *clk, uint64_t freq)
> +{
> +    ClockIn *follower;
> +    trace_clock_update(CLOCK_PATH(clk), freq);

Maybe the function name makes sens: trace_clock_set_frequency()

> +
> +    QLIST_FOREACH(follower, &clk->followers, sibling) {
> +        trace_clock_propagate(CLOCK_PATH(clk), CLOCK_PATH(follower));
> +        if (follower->frequency != freq) {
> +            follower->frequency = freq;
> +            if (follower->callback) {
> +                follower->callback(follower->callback_opaque);
> +            }
> +        }
> +    }
> +}
> +
> +static void clock_out_initfn(Object *obj)
> +{
> +    ClockOut *clk = CLOCK_OUT(obj);
> +
> +    QLIST_INIT(&clk->followers);
> +}
> +
> +static void clock_out_finalizefn(Object *obj)
> +{
> +    ClockOut *clk = CLOCK_OUT(obj);
> +    ClockIn *follower, *next;
> +
> +    /* clear our list of followers */
> +    QLIST_FOREACH_SAFE(follower, &clk->followers, sibling, next) {
> +        clock_disconnect(follower);
> +    }
> +
> +    g_free(clk->canonical_path);
> +    clk->canonical_path = NULL;
> +}
> +
> +static void clock_in_finalizefn(Object *obj)
> +{
> +    ClockIn *clk = CLOCK_IN(obj);
> +
> +    /* remove us from driver's followers list */
> +    clock_disconnect(clk);
> +
> +    g_free(clk->canonical_path);
> +    clk->canonical_path = NULL;
> +}
> +
> +static const TypeInfo clock_out_info = {
> +    .name              = TYPE_CLOCK_OUT,
> +    .parent            = TYPE_OBJECT,
> +    .instance_size     = sizeof(ClockOut),
> +    .instance_init     = clock_out_initfn,
> +    .instance_finalize = clock_out_finalizefn,
> +};
> +
> +static const TypeInfo clock_in_info = {
> +    .name              = TYPE_CLOCK_IN,
> +    .parent            = TYPE_OBJECT,
> +    .instance_size     = sizeof(ClockIn),
> +    .instance_finalize = clock_in_finalizefn,
> +};
> +
> +static void clock_register_types(void)
> +{
> +    type_register_static(&clock_in_info);
> +    type_register_static(&clock_out_info);
> +}
> +
> +type_init(clock_register_types)
> diff --git a/hw/core/Makefile.objs b/hw/core/Makefile.objs
> index eb88ca979e..f7102121f4 100644
> --- a/hw/core/Makefile.objs
> +++ b/hw/core/Makefile.objs
> @@ -6,6 +6,7 @@ common-obj-$(CONFIG_SOFTMMU) += fw-path-provider.o
>  # irq.o needed for qdev GPIO handling:
>  common-obj-y += irq.o
>  common-obj-y += hotplug.o
> +common-obj-y += clock-port.o
>  common-obj-$(CONFIG_SOFTMMU) += nmi.o
>  
>  common-obj-$(CONFIG_EMPTY_SLOT) += empty_slot.o
> diff --git a/hw/core/trace-events b/hw/core/trace-events
> new file mode 100644
> index 0000000000..d4880ec138
> --- /dev/null
> +++ b/hw/core/trace-events
> @@ -0,0 +1,7 @@
> +# See docs/devel/tracing.txt for syntax documentation.
> +
> +# hw/core/clock-port.c
> +clock_connect(const char *clk, const char *driver) "'%s' drived-by '%s'"
> +clock_disconnect(const char *clk) "'%s'"
> +clock_update(const char *clk, uint64_t freq) "'%s' frequency %" PRIu64 "Hz"
> +clock_propagate(const char *clko, const char *clki) "'%s' => '%s'"
> 

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>