target/xtensa: refactor CCOUNT/CCOMPARE

Xtensa cores may have a register (CCOUNT) that counts core clock cycles.
It may also have a number of registers (CCOMPAREx); when CCOUNT value
passes the value of CCOMPAREx, timer interrupt x is raised.

Currently xtensa target counts a number of completed instructions and
assumes that for CCOUNT one instruction takes one cycle to complete.
It calls helper function to update CCOUNT register at every TB end and
raise timer interrupts. This scheme works very predictably and doesn't
have noticeable performance impact, but it is hard to use with multiple
synchronized processors, especially with coming MTTCG.

Derive CCOUNT from the virtual simulation time, QEMU_CLOCK_VIRTUAL.
Use native QEMU timers for CCOMPARE timers, one timer for each register.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

1 files changed, 25 insertions, 8 deletions

diff --git a/target/xtensa/op_helper.c b/target/xtensa/op_helper.c
index 0a4b2147bc..5e5c7da010 100644
--- a/target/xtensa/op_helper.c
+++ b/target/xtensa/op_helper.c
@@ -398,22 +398,39 @@ void HELPER(waiti)(CPUXtensaState *env, uint32_t pc, uint32_t intlevel)
     }
 
     cpu = CPU(xtensa_env_get_cpu(env));
-    env->halt_clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
     cpu->halted = 1;
-    if (xtensa_option_enabled(env->config, XTENSA_OPTION_TIMER_INTERRUPT)) {
-        xtensa_rearm_ccompare_timer(env);
-    }
     HELPER(exception)(env, EXCP_HLT);
 }
 
-void HELPER(timer_irq)(CPUXtensaState *env, uint32_t id, uint32_t active)
+void HELPER(update_ccount)(CPUXtensaState *env)
+{
+    uint64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+
+    env->ccount_time = now;
+    env->sregs[CCOUNT] = env->ccount_base +
+        (uint32_t)((now - env->time_base) *
+                   env->config->clock_freq_khz / 1000000);
+}
+
+void HELPER(wsr_ccount)(CPUXtensaState *env, uint32_t v)
 {
-    xtensa_timer_irq(env, id, active);
+    int i;
+
+    HELPER(update_ccount)(env);
+    env->ccount_base += v - env->sregs[CCOUNT];
+    for (i = 0; i < env->config->nccompare; ++i) {
+        HELPER(update_ccompare)(env, i);
+    }
 }
 
-void HELPER(advance_ccount)(CPUXtensaState *env, uint32_t d)
+void HELPER(update_ccompare)(CPUXtensaState *env, uint32_t i)
 {
-    xtensa_advance_ccount(env, d);
+    uint64_t dcc;
+
+    HELPER(update_ccount)(env);
+    dcc = (uint64_t)(env->sregs[CCOMPARE + i] - env->sregs[CCOUNT] - 1) + 1;
+    timer_mod(env->ccompare[i].timer,
+              env->ccount_time + (dcc * 1000000) / env->config->clock_freq_khz);
 }
 
 void HELPER(check_interrupts)(CPUXtensaState *env)