target/imx: reload cmp timer outside of the reload ptimer transaction

When running seL4 tests (https://docs.sel4.systems/projects/sel4test)
on the sabrelight platform, the timer tests fail. The arm/imx6 EPIT
timer interrupt does not fire properly, instead of a e.g. second in
can take up to a minute to finally see the interrupt.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1263

Signed-off-by: Axel Heider <axel.heider@hensoldt.net>
Message-id: 166663118138.13362.1229967229046092876-0@git.sr.ht
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/timer/imx_epit.c

@@ -275,10 +275,15 @@ static void imx_epit_write(void *opaque, hwaddr offset, uint64_t value,
             /* If IOVW bit is set then set the timer value */
             ptimer_set_count(s->timer_reload, s->lr);
         }
-
+        /*
+         * Commit the change to s->timer_reload, so it can propagate. Otherwise
+         * the timer interrupt may not fire properly. The commit must happen
+         * before calling imx_epit_reload_compare_timer(), which reads
+         * s->timer_reload internally again.
+         */
+        ptimer_transaction_commit(s->timer_reload);
         imx_epit_reload_compare_timer(s);
         ptimer_transaction_commit(s->timer_cmp);
-        ptimer_transaction_commit(s->timer_reload);
         break;
 
     case 3: /* CMP */