[RFC PATCH-for-6.1 5/9] hw/core/qdev-clock: Add qdev_ground_clock() helper

[Philippe Mathieu-Daudé]

Clocks are rarely left unconnected, but rather connected to ground
plane to avoid noise. When representing the clock tree, we want to
see such ground clock. As we might reuse this clock on various
boards, introduce the qdev_ground_clock() which return a singleton
ground clock.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 include/hw/qdev-clock.h |  9 +++++++++
 hw/core/qdev-clock.c    | 11 +++++++++++
 2 files changed, 20 insertions(+)

diff --git a/include/hw/qdev-clock.h b/include/hw/qdev-clock.h
index ffa0f7ba09e..2f2d2da6cd6 100644
--- a/include/hw/qdev-clock.h
+++ b/include/hw/qdev-clock.h
@@ -161,4 +161,13 @@ typedef struct ClockPortInitElem ClockPortInitArray[];
  */
 void qdev_init_clocks(DeviceState *dev, const ClockPortInitArray clocks);
 
+/**
+ * qdev_ground_clock:
+ * @returns: a pointer to the ground clock
+ *
+ * Get the special 'ground' clock. This clock can be used as input
+ * (unclocked) or output.
+ */
+Clock *qdev_ground_clock(void);
+
 #endif /* QDEV_CLOCK_H */
diff --git a/hw/core/qdev-clock.c b/hw/core/qdev-clock.c
index 117f4c6ea4a..a46384a84b7 100644
--- a/hw/core/qdev-clock.c
+++ b/hw/core/qdev-clock.c
@@ -210,3 +210,14 @@ void qdev_connect_clock_in(DeviceState *dev, const char 
*name, Clock *source)
     assert(!dev->realized);
     clock_set_source(qdev_get_clock_in(dev, name), source);
 }
+
+Clock *qdev_ground_clock(void)
+{
+    static Clock *gnd_clk;
+
+    if (!gnd_clk) {
+        gnd_clk = clock_new(qdev_get_machine(), "gnd");
+    }
+
+    return gnd_clk;
+}
-- 
2.26.3