target/mips/cpu: Display warning when CPU is used without input clock

All our QOM users provides an input clock. In order to avoid
avoid future machines added without clock, display a warning.

User-mode emulation use the CP0 timer with the RDHWR instruction
(see commit cdfcad7883) so keep using the fixed 200 MHz clock
without diplaying any warning. Only display it in system-mode
emulation.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20201012095804.3335117-22-f4bug@amsat.org>

target/mips/cpu.c

@@ -19,12 +19,14 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/cutils.h"
 #include "qapi/error.h"
 #include "cpu.h"
 #include "internal.h"
 #include "kvm_mips.h"
 #include "qemu/module.h"
 #include "sysemu/kvm.h"
+#include "sysemu/qtest.h"
 #include "exec/exec-all.h"
 #include "hw/qdev-properties.h"
 #include "hw/qdev-clock.h"
@@ -158,6 +160,14 @@ static void mips_cpu_realizefn(DeviceState *dev, Error **errp)
     Error *local_err = NULL;
 
     if (!clock_get(cpu->clock)) {
+#ifndef CONFIG_USER_ONLY
+        if (!qtest_enabled()) {
+            g_autofree char *cpu_freq_str = freq_to_str(CPU_FREQ_HZ_DEFAULT);
+
+            warn_report("CPU input clock is not connected to any output clock, "
+                        "using default frequency of %s.", cpu_freq_str);
+        }
+#endif
         /* Initialize the frequency in case the clock remains unconnected. */
         clock_set_hz(cpu->clock, CPU_FREQ_HZ_DEFAULT);
     }