hw/intc: Fix upper/lower mtime write calculation

When writing the upper mtime, we should keep the original lower mtime
whose value is given by cpu_riscv_read_rtc() instead of
cpu_riscv_read_rtc_raw(). The same logic applies to writes to lower mtime.

Signed-off-by: Jason Chien <jason.chien@sifive.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20230728082502.26439-1-jason.chien@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

hw/intc/riscv_aclint.c

@@ -208,11 +208,12 @@ static void riscv_aclint_mtimer_write(void *opaque, hwaddr addr,
         return;
     } else if (addr == mtimer->time_base || addr == mtimer->time_base + 4) {
         uint64_t rtc_r = cpu_riscv_read_rtc_raw(mtimer->timebase_freq);
+        uint64_t rtc = cpu_riscv_read_rtc(mtimer);
 
         if (addr == mtimer->time_base) {
             if (size == 4) {
                 /* time_lo for RV32/RV64 */
-                mtimer->time_delta = ((rtc_r & ~0xFFFFFFFFULL) | value) - rtc_r;
+                mtimer->time_delta = ((rtc & ~0xFFFFFFFFULL) | value) - rtc_r;
             } else {
                 /* time for RV64 */
                 mtimer->time_delta = value - rtc_r;
@@ -220,7 +221,7 @@ static void riscv_aclint_mtimer_write(void *opaque, hwaddr addr,
         } else {
             if (size == 4) {
                 /* time_hi for RV32/RV64 */
-                mtimer->time_delta = (value << 32 | (rtc_r & 0xFFFFFFFF)) - rtc_r;
+                mtimer->time_delta = (value << 32 | (rtc & 0xFFFFFFFF)) - rtc_r;
             } else {
                 qemu_log_mask(LOG_GUEST_ERROR,
                               "aclint-mtimer: invalid time_hi write: %08x",