hw/intc: riscv_aclint: Add reset function of ACLINT devices

This commit implements reset function of all ACLINT devices.
ACLINT device reset will clear MTIME and MSIP register to 0.

Depend on RISC-V ACLINT spec v1.0-rc4:
https://github.com/riscv/riscv-aclint/blob/v1.0-rc4/riscv-aclint.adoc

Signed-off-by: Jim Shu <jim.shu@sifive.com>
Reviewed-by: Frank Chang <frank.chang@sifive.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20220420080901.14655-5-frank.chang@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

hw/intc/riscv_aclint.c

@@ -293,11 +293,29 @@ static void riscv_aclint_mtimer_realize(DeviceState *dev, Error **errp)
     }
 }
 
+static void riscv_aclint_mtimer_reset_enter(Object *obj, ResetType type)
+{
+    /*
+     * According to RISC-V ACLINT spec:
+     *   - On MTIMER device reset, the MTIME register is cleared to zero.
+     *   - On MTIMER device reset, the MTIMECMP registers are in unknown state.
+     */
+    RISCVAclintMTimerState *mtimer = RISCV_ACLINT_MTIMER(obj);
+
+    /*
+     * Clear mtime register by writing to 0 it.
+     * Pending mtime interrupts will also be cleared at the same time.
+     */
+    riscv_aclint_mtimer_write(mtimer, mtimer->time_base, 0, 8);
+}
+
 static void riscv_aclint_mtimer_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
     dc->realize = riscv_aclint_mtimer_realize;
     device_class_set_props(dc, riscv_aclint_mtimer_properties);
+    ResettableClass *rc = RESETTABLE_CLASS(klass);
+    rc->phases.enter = riscv_aclint_mtimer_reset_enter;
 }
 
 static const TypeInfo riscv_aclint_mtimer_info = {
@@ -452,11 +470,32 @@ static void riscv_aclint_swi_realize(DeviceState *dev, Error **errp)
     }
 }
 
+static void riscv_aclint_swi_reset_enter(Object *obj, ResetType type)
+{
+    /*
+     * According to RISC-V ACLINT spec:
+     *   - On MSWI device reset, each MSIP register is cleared to zero.
+     *
+     * p.s. SSWI device reset does nothing since SETSIP register always reads 0.
+     */
+    RISCVAclintSwiState *swi = RISCV_ACLINT_SWI(obj);
+    int i;
+
+    if (!swi->sswi) {
+        for (i = 0; i < swi->num_harts; i++) {
+            /* Clear MSIP registers by lowering software interrupts. */
+            qemu_irq_lower(swi->soft_irqs[i]);
+        }
+    }
+}
+
 static void riscv_aclint_swi_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
     dc->realize = riscv_aclint_swi_realize;
     device_class_set_props(dc, riscv_aclint_swi_properties);
+    ResettableClass *rc = RESETTABLE_CLASS(klass);
+    rc->phases.enter = riscv_aclint_swi_reset_enter;
 }
 
 static const TypeInfo riscv_aclint_swi_info = {