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, 14 insertions, 61 deletions

diff --git a/hw/xtensa/pic_cpu.c b/hw/xtensa/pic_cpu.c
index 2bed64f..0e812d7 100644
--- a/hw/xtensa/pic_cpu.c
+++ b/hw/xtensa/pic_cpu.c
@@ -31,22 +31,6 @@
 #include "qemu/log.h"
 #include "qemu/timer.h"
 
-void xtensa_advance_ccount(CPUXtensaState *env, uint32_t d)
-{
-    uint32_t old_ccount = env->sregs[CCOUNT] + 1;
-
-    env->sregs[CCOUNT] += d;
-
-    if (xtensa_option_enabled(env->config, XTENSA_OPTION_TIMER_INTERRUPT)) {
-        int i;
-        for (i = 0; i < env->config->nccompare; ++i) {
-            if (env->sregs[CCOMPARE + i] - old_ccount < d) {
-                xtensa_timer_irq(env, i, 1);
-            }
-        }
-    }
-}
-
 void check_interrupts(CPUXtensaState *env)
 {
     CPUState *cs = CPU(xtensa_env_get_cpu(env));
@@ -54,17 +38,6 @@ void check_interrupts(CPUXtensaState *env)
     uint32_t int_set_enabled = env->sregs[INTSET] & env->sregs[INTENABLE];
     int level;
 
-    /* If the CPU is halted advance CCOUNT according to the QEMU_CLOCK_VIRTUAL time
-     * elapsed since the moment when it was advanced last time.
-     */
-    if (cs->halted) {
-        int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
-
-        xtensa_advance_ccount(env,
-                muldiv64(now - env->halt_clock,
-                    env->config->clock_freq_khz, 1000000));
-        env->halt_clock = now;
-    }
     for (level = env->config->nlevel; level > minlevel; --level) {
         if (env->config->level_mask[level] & int_set_enabled) {
             env->pending_irq_level = level;
@@ -109,49 +82,29 @@ void xtensa_timer_irq(CPUXtensaState *env, uint32_t id, uint32_t active)
     qemu_set_irq(env->irq_inputs[env->config->timerint[id]], active);
 }
 
-void xtensa_rearm_ccompare_timer(CPUXtensaState *env)
-{
-    int i;
-    uint32_t wake_ccount = env->sregs[CCOUNT] - 1;
-
-    for (i = 0; i < env->config->nccompare; ++i) {
-        if (env->sregs[CCOMPARE + i] - env->sregs[CCOUNT] <
-                wake_ccount - env->sregs[CCOUNT]) {
-            wake_ccount = env->sregs[CCOMPARE + i];
-        }
-    }
-    env->wake_ccount = wake_ccount;
-    timer_mod(env->ccompare_timer, env->halt_clock +
-            (uint64_t)(wake_ccount - env->sregs[CCOUNT]) *
-            1000000 / env->config->clock_freq_khz);
-}
-
 static void xtensa_ccompare_cb(void *opaque)
 {
-    XtensaCPU *cpu = opaque;
-    CPUXtensaState *env = &cpu->env;
-    CPUState *cs = CPU(cpu);
+    XtensaCcompareTimer *ccompare = opaque;
+    CPUXtensaState *env = ccompare->env;
+    unsigned i = ccompare - env->ccompare;
 
-    if (cs->halted) {
-        env->halt_clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
-        xtensa_advance_ccount(env, env->wake_ccount - env->sregs[CCOUNT]);
-        if (!cpu_has_work(cs)) {
-            env->sregs[CCOUNT] = env->wake_ccount + 1;
-            xtensa_rearm_ccompare_timer(env);
-        }
-    }
+    xtensa_timer_irq(env, i, 1);
 }
 
 void xtensa_irq_init(CPUXtensaState *env)
 {
-    XtensaCPU *cpu = xtensa_env_get_cpu(env);
-
     env->irq_inputs = (void **)qemu_allocate_irqs(
             xtensa_set_irq, env, env->config->ninterrupt);
-    if (xtensa_option_enabled(env->config, XTENSA_OPTION_TIMER_INTERRUPT) &&
-            env->config->nccompare > 0) {
-        env->ccompare_timer =
-            timer_new_ns(QEMU_CLOCK_VIRTUAL, &xtensa_ccompare_cb, cpu);
+    if (xtensa_option_enabled(env->config, XTENSA_OPTION_TIMER_INTERRUPT)) {
+        unsigned i;
+
+        env->time_base = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+        env->ccount_base = env->sregs[CCOUNT];
+        for (i = 0; i < env->config->nccompare; ++i) {
+            env->ccompare[i].env = env;
+            env->ccompare[i].timer = timer_new_ns(QEMU_CLOCK_VIRTUAL,
+                    xtensa_ccompare_cb, env->ccompare + i);
+        }
     }
 }