[Qemu-devel] [PATCH, MIPS R2] Timer start/stop implementation

[Aurelien Jarno]

Hi all,

The patch below allows the timer to be stopped using the DC bit in the 
CP0 Cause register. This feature is required for MIPS R2 implementations.

It also removes a few places where the interrupt corresponding to the 
timer is hardcoded, and leaves it hardcoded at only one place 
(initialisation).

Bye,
Aurelien

Index: hw/mips_timer.c
===================================================================
RCS file: /sources/qemu/qemu/hw/mips_timer.c,v
retrieving revision 1.7
diff -u -d -p -r1.7 mips_timer.c
--- hw/mips_timer.c     6 Sep 2007 00:18:14 -0000       1.7
+++ hw/mips_timer.c     24 Sep 2007 13:22:50 -0000
@@ -17,9 +17,12 @@ uint32_t cpu_mips_get_random (CPUState *
 /* MIPS R4K timer */
 uint32_t cpu_mips_get_count (CPUState *env)
 {
-    return env->CP0_Count +
-        (uint32_t)muldiv64(qemu_get_clock(vm_clock),
-                           100 * 1000 * 1000, ticks_per_sec);
+    if (env->CP0_Cause & (1 << CP0Ca_DC))
+        return env->CP0_Count;
+    else
+        return env->CP0_Count +
+            (uint32_t)muldiv64(qemu_get_clock(vm_clock),
+                               100 * 1000 * 1000, ticks_per_sec);
 }
 
 void cpu_mips_store_count (CPUState *env, uint32_t count)
@@ -63,7 +66,19 @@ void cpu_mips_store_compare (CPUState *e
     cpu_mips_update_count(env, cpu_mips_get_count(env));
     if ((env->CP0_Config0 & (0x7 << CP0C0_AR)) == (1 << CP0C0_AR))
         env->CP0_Cause &= ~(1 << CP0Ca_TI);
-    qemu_irq_lower(env->irq[7]);
+    qemu_irq_lower(env->irq[(env->CP0_IntCtl >> CP0In_IPTI) & 0x7]);
+}
+
+void cpu_mips_start_count(CPUState *env)
+{
+    cpu_mips_store_count(env, env->CP0_Count);
+}
+
+void cpu_mips_stop_count(CPUState *env)
+{
+    /* Store the current value */
+    env->CP0_Count += (uint32_t)muldiv64(qemu_get_clock(vm_clock),
+                                         100 * 1000 * 1000, ticks_per_sec);
 }
 
 static void mips_timer_cb (void *opaque)
@@ -76,10 +91,14 @@ static void mips_timer_cb (void *opaque)
         fprintf(logfile, "%s\n", __func__);
     }
 #endif
+
+    if (env->CP0_Cause & (1 << CP0Ca_DC))
+        return;
+
     cpu_mips_update_count(env, cpu_mips_get_count(env));
     if ((env->CP0_Config0 & (0x7 << CP0C0_AR)) == (1 << CP0C0_AR))
         env->CP0_Cause |= 1 << CP0Ca_TI;
-    qemu_irq_raise(env->irq[7]);
+    qemu_irq_raise(env->irq[(env->CP0_IntCtl >> CP0In_IPTI) & 0x7]);
 }
 
 void cpu_mips_clock_init (CPUState *env)
Index: target-mips/exec.h
===================================================================
RCS file: /sources/qemu/qemu/target-mips/exec.h,v
retrieving revision 1.32
diff -u -d -p -r1.32 exec.h
--- target-mips/exec.h  16 Sep 2007 21:08:03 -0000      1.32
+++ target-mips/exec.h  24 Sep 2007 13:22:50 -0000
@@ -153,6 +153,8 @@ uint32_t cpu_mips_get_random (CPUState *
 uint32_t cpu_mips_get_count (CPUState *env);
 void cpu_mips_store_count (CPUState *env, uint32_t value);
 void cpu_mips_store_compare (CPUState *env, uint32_t value);
+void cpu_mips_start_count(CPUState *env);
+void cpu_mips_stop_count(CPUState *env);
 void cpu_mips_update_irq (CPUState *env);
 void cpu_mips_clock_init (CPUState *env);
 void cpu_mips_tlb_flush (CPUState *env, int flush_global);
Index: target-mips/op.c
===================================================================
RCS file: /sources/qemu/qemu/target-mips/op.c,v
retrieving revision 1.72
diff -u -d -p -r1.72 op.c
--- target-mips/op.c    24 Sep 2007 12:48:00 -0000      1.72
+++ target-mips/op.c    24 Sep 2007 13:22:51 -0000
@@ -1882,9 +1882,8 @@ void op_mttc0_status(void)
 
 void op_mtc0_intctl (void)
 {
-    /* vectored interrupts not implemented, timer on int 7,
-       no performance counters. */
-    env->CP0_IntCtl |= T0 & 0x000002e0;
+    /* vectored interrupts not implemented, no performance counters. */
+    env->CP0_IntCtl = (env->CP0_IntCtl & ~0x000002e0) | (T0 & 0x000002e0);
     RETURN();
 }
 
@@ -1904,12 +1903,20 @@ void op_mtc0_srsmap (void)
 void op_mtc0_cause (void)
 {
     uint32_t mask = 0x00C00300;
+    uint32_t old = env->CP0_Cause;
 
     if (env->insn_flags & ISA_MIPS32R2)
         mask |= 1 << CP0Ca_DC;
 
     env->CP0_Cause = (env->CP0_Cause & ~mask) | (T0 & mask);
 
+    if ((old ^ env->CP0_Cause) & (1 << CP0Ca_DC)) {
+        if (env->CP0_Cause & (1 << CP0Ca_DC))
+            CALL_FROM_TB1(cpu_mips_stop_count, env);
+        else
+            CALL_FROM_TB1(cpu_mips_start_count, env);  
+    }
+
     /* Handle the software interrupt as an hardware one, as they
        are very similar */
     if (T0 & CP0Ca_IP_mask) {
Index: target-mips/op_helper.c
===================================================================
RCS file: /sources/qemu/qemu/target-mips/op_helper.c,v
retrieving revision 1.59
diff -u -d -p -r1.59 op_helper.c
--- target-mips/op_helper.c     17 Sep 2007 08:09:53 -0000      1.59
+++ target-mips/op_helper.c     24 Sep 2007 13:22:52 -0000
@@ -265,6 +265,16 @@ void cpu_mips_store_compare(CPUState *en
     cpu_abort(env, "mtc0 compare\n");
 }
 
+void cpu_mips_start_count(CPUState *env)
+{
+    cpu_abort(env, "start count\n");
+}
+
+void cpu_mips_stop_count(CPUState *env)
+{
+    cpu_abort(env, "stop count\n");
+}
+
 void cpu_mips_update_irq(CPUState *env)
 {
     cpu_abort(env, "mtc0 status / mtc0 cause\n");

-- 
  .''`.  Aurelien Jarno             | GPG: 1024D/F1BCDB73
 : :' :  Debian developer           | Electrical Engineer
 `. `'   address@hidden         | address@hidden
   `-    people.debian.org/~aurel32 | www.aurel32.net