target/mips/cpu: Allow the CPU to use dynamic frequencies

Use the Clock API and let the CPU object have an input clock.

If no clock is connected, keep using the default frequency of
200 MHz used since the introduction of the 'r4k' machine in
commit 6af0bf9c7c3.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20201012095804.3335117-12-f4bug@amsat.org>

2 files changed, 13 insertions, 2 deletions

diff --git a/target/mips/cpu.c b/target/mips/cpu.c
index 461edfe..2a6f484 100644
--- a/target/mips/cpu.c
+++ b/target/mips/cpu.c
@@ -27,6 +27,7 @@
 #include "sysemu/kvm.h"
 #include "exec/exec-all.h"
 #include "hw/qdev-properties.h"
+#include "hw/qdev-clock.h"
 
 static void mips_cpu_set_pc(CPUState *cs, vaddr value)
 {
@@ -144,8 +145,9 @@ static void mips_cp0_period_set(MIPSCPU *cpu)
 {
     CPUMIPSState *env = &cpu->env;
 
-    env->cp0_count_ns = muldiv64(NANOSECONDS_PER_SECOND, cpu->cp0_count_rate,
-                                 CPU_FREQ_HZ_DEFAULT);
+    env->cp0_count_ns = cpu->cp0_count_rate
+                        * clock_get_ns(MIPS_CPU(cpu)->clock);
+    assert(env->cp0_count_ns);
 }
 
 static void mips_cpu_realizefn(DeviceState *dev, Error **errp)
@@ -155,6 +157,10 @@ static void mips_cpu_realizefn(DeviceState *dev, Error **errp)
     MIPSCPUClass *mcc = MIPS_CPU_GET_CLASS(dev);
     Error *local_err = NULL;
 
+    if (!clock_get(cpu->clock)) {
+        /* Initialize the frequency in case the clock remains unconnected. */
+        clock_set_hz(cpu->clock, CPU_FREQ_HZ_DEFAULT);
+    }
     mips_cp0_period_set(cpu);
 
     cpu_exec_realizefn(cs, &local_err);
@@ -178,6 +184,7 @@ static void mips_cpu_initfn(Object *obj)
     MIPSCPUClass *mcc = MIPS_CPU_GET_CLASS(obj);
 
     cpu_set_cpustate_pointers(cpu);
+    cpu->clock = qdev_init_clock_in(DEVICE(obj), "clk-in", NULL, cpu);
     env->cpu_model = mcc->cpu_def;
 }
 
diff --git a/target/mips/cpu.h b/target/mips/cpu.h
index baeceb8..062a4ba 100644
--- a/target/mips/cpu.h
+++ b/target/mips/cpu.h
@@ -4,6 +4,7 @@
 #include "cpu-qom.h"
 #include "exec/cpu-defs.h"
 #include "fpu/softfloat-types.h"
+#include "hw/clock.h"
 #include "mips-defs.h"
 
 #define TCG_GUEST_DEFAULT_MO (0)
@@ -1151,6 +1152,8 @@ struct CPUMIPSState {
 /**
  * MIPSCPU:
  * @env: #CPUMIPSState
+ * @clock: this CPU input clock (may be connected
+ *         to an output clock from another device).
  * @cp0_count_rate: rate at which the coprocessor 0 counter increments
  *
  * A MIPS CPU.
@@ -1160,6 +1163,7 @@ struct MIPSCPU {
     CPUState parent_obj;
     /*< public >*/
 
+    Clock *clock;
     CPUNegativeOffsetState neg;
     CPUMIPSState env;
     /*