Expose the clock period via the QOM 'qtest-clock-period' property so it
can be used in QTests. This property is only accessible in QTests (not
via HMP).

Signed-off-by: Inès Varhol <ines.varhol@telecom-paris.fr>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Luc Michel <luc@lmichel.fr>
---
 docs/devel/clocks.rst |  6 ++++++
 hw/core/clock.c       | 16 ++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/docs/devel/clocks.rst b/docs/devel/clocks.rst
index 177ee1c90d..3f744f2be1 100644
--- a/docs/devel/clocks.rst
+++ b/docs/devel/clocks.rst
@@ -358,6 +358,12 @@ humans (for instance in debugging), use ``clock_display_freq()``,
 which returns a prettified string-representation, e.g. "33.3 MHz".
 The caller must free the string with g_free() after use.
 
+It's also possible to retrieve the clock period from a QTest by
+accessing QOM property ``qtest-clock-period`` using a QMP command.
+This property is only present when the device is being run under
+the ``qtest`` accelerator; it is not available when QEMU is
+being run normally.
+
 Calculating expiry deadlines
 ----------------------------
 
diff --git a/hw/core/clock.c b/hw/core/clock.c
index e212865307..cbe7b1bc46 100644
--- a/hw/core/clock.c
+++ b/hw/core/clock.c
@@ -13,6 +13,8 @@
 
 #include "qemu/osdep.h"
 #include "qemu/cutils.h"
+#include "qapi/visitor.h"
+#include "sysemu/qtest.h"
 #include "hw/clock.h"
 #include "trace.h"
 
@@ -158,6 +160,15 @@ bool clock_set_mul_div(Clock *clk, uint32_t multiplier, uint32_t divider)
     return true;
 }
 
+static void clock_period_prop_get(Object *obj, Visitor *v, const char *name,
+                                void *opaque, Error **errp)
+{
+    Clock *clk = CLOCK(obj);
+    uint64_t period = clock_get(clk);
+    visit_type_uint64(v, name, &period, errp);
+}
+
+
 static void clock_initfn(Object *obj)
 {
     Clock *clk = CLOCK(obj);
@@ -166,6 +177,11 @@ static void clock_initfn(Object *obj)
     clk->divider = 1;
 
     QLIST_INIT(&clk->children);
+
+    if (qtest_enabled()) {
+        object_property_add(obj, "qtest-clock-period", "uint64",
+                            clock_period_prop_get, NULL, NULL, NULL);
+    }
 }
 
 static void clock_finalizefn(Object *obj)
-- 
2.43.2