Preparation commit to let aclint timer to use stimecmp write function.
Aclint timer doesn't call sstc() predicate so we need to check inside
the stimecmp write function.

Signed-off-by: Jim Shu <jim.shu@sifive.com>
---
 target/riscv/time_helper.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/target/riscv/time_helper.c b/target/riscv/time_helper.c
index bc0d9a0c4c..aebf0798d0 100644
--- a/target/riscv/time_helper.c
+++ b/target/riscv/time_helper.c
@@ -46,8 +46,23 @@ void riscv_timer_write_timecmp(CPURISCVState *env, QEMUTimer *timer,
 {
     uint64_t diff, ns_diff, next;
     RISCVAclintMTimerState *mtimer = env->rdtime_fn_arg;
-    uint32_t timebase_freq = mtimer->timebase_freq;
-    uint64_t rtc_r = env->rdtime_fn(env->rdtime_fn_arg) + delta;
+    uint32_t timebase_freq;
+    uint64_t rtc_r;
+
+    if (!riscv_cpu_cfg(env)->ext_sstc || !env->rdtime_fn ||
+        !env->rdtime_fn_arg || !get_field(env->menvcfg, MENVCFG_STCE)) {
+        /* S/VS Timer IRQ depends on sstc extension, rdtime_fn(), and STCE. */
+        return;
+    }
+
+    if (timer_irq == MIP_VSTIP &&
+        (!riscv_has_ext(env, RVH) || !get_field(env->henvcfg, HENVCFG_STCE))) {
+        /* VS Timer IRQ also depends on RVH and henvcfg.STCE. */
+        return;
+    }
+
+    timebase_freq = mtimer->timebase_freq;
+    rtc_r = env->rdtime_fn(env->rdtime_fn_arg) + delta;
 
     if (timecmp <= rtc_r) {
         /*
-- 
2.17.1