hw/clock: Let clock_set() return boolean value

Let clock_set() return a boolean value whether the clock
has been updated or not.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200806123858.30058-3-f4bug@amsat.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/core/clock.c

@@ -34,11 +34,16 @@ void clock_clear_callback(Clock *clk)
     clock_set_callback(clk, NULL, NULL);
 }
 
-void clock_set(Clock *clk, uint64_t period)
+bool clock_set(Clock *clk, uint64_t period)
 {
+    if (clk->period == period) {
+        return false;
+    }
     trace_clock_set(CLOCK_PATH(clk), CLOCK_PERIOD_TO_NS(clk->period),
                     CLOCK_PERIOD_TO_NS(period));
     clk->period = period;
+
+    return true;
 }
 
 static void clock_propagate_period(Clock *clk, bool call_callbacks)

include/hw/clock.h

@@ -127,17 +127,19 @@ void clock_set_source(Clock *clk, Clock *src);
  * @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.
  */
-void clock_set(Clock *clk, uint64_t value);
+bool clock_set(Clock *clk, uint64_t value);
 
-static inline void clock_set_hz(Clock *clk, unsigned hz)
+static inline bool clock_set_hz(Clock *clk, unsigned hz)
 {
-    clock_set(clk, CLOCK_PERIOD_FROM_HZ(hz));
+    return clock_set(clk, CLOCK_PERIOD_FROM_HZ(hz));
 }
 
-static inline void clock_set_ns(Clock *clk, unsigned ns)
+static inline bool clock_set_ns(Clock *clk, unsigned ns)
 {
-    clock_set(clk, CLOCK_PERIOD_FROM_NS(ns));
+    return clock_set(clk, CLOCK_PERIOD_FROM_NS(ns));
 }
 
 /**