[ot] hw/opentitan: ot_alert: Connect alert phase 0 NMI

In escalation phase 0, the alert handler sends an NMI to the CPU, which
will interrupt execution so long as the NMI is enabled in Ibex itself.
As such, we connect this functionality in the alert handler.

See: https://opentitan.org/book/sw/device/silicon_creator/rom/doc/shutdown.html#alert-escalation-phase-actions

Signed-off-by: Alex Jones <[email protected]>

Author: AlexJones0

hw/opentitan/ot_alert.c

@@ -220,6 +220,7 @@ struct OtAlertState {
     MemoryRegion mmio;
     IbexIRQ *irqs;
     IbexIRQ *esc_txs;
+    IbexIRQ nmi_alert;
     OtAlertScheduler *schedulers;
 
     OtAlertRegs regs; /* not ordered by register index */
@@ -571,6 +572,7 @@ static void ot_alert_clear_alert(OtAlertState *s, unsigned nclass)
             trace_ot_alert_escalation(s->ot_id, ACLASS(nclass), ix, "release");
         }
         ibex_irq_set(esc_tx, 0);
+        ibex_irq_set(&s->nmi_alert, 0u);
     }
     /*
      * "Software can clear CLASSn_ACCUM_CNT with a write to CLASSA_CLR_SHADOWED"
@@ -741,6 +743,10 @@ static void ot_alert_signal_tx(void *opaque, int n, int level)
 
     trace_ot_alert_signal_tx(s->ot_id, alert, (bool)level, alert_en);
 
+    if (alert_en && level) {
+        ibex_irq_set(&s->nmi_alert, 1u);
+    }
+
     if (!alert_en || !level) {
         /* releasing the alert does not clear it */
         return;
@@ -1034,6 +1040,7 @@ static void ot_alert_realize(DeviceState *dev, Error **errp)
     s->esc_txs = g_new0(IbexIRQ, PARAM_N_ESC_SEV);
     ibex_qdev_init_irqs(OBJECT(dev), s->esc_txs, OT_ALERT_ESCALATE,
                         PARAM_N_ESC_SEV);
+    ibex_qdev_init_irq(OBJECT(dev), &s->nmi_alert, OT_ALERT_NMI);
 
     qdev_init_gpio_in_named(dev, &ot_alert_signal_tx, OT_DEVICE_ALERT,
                             s->n_alerts);

hw/riscv/ot_earlgrey.c

@@ -640,7 +640,9 @@ static const IbexDeviceDef ot_eg_soc_devices[] = {
             OT_EG_SOC_GPIO_ESCALATE(0, IBEX_WRAPPER, 0),
             OT_EG_SOC_GPIO_ESCALATE(1, LC_CTRL, 0),
             OT_EG_SOC_GPIO_ESCALATE(1, LC_CTRL, 1),
-            OT_EG_SOC_GPIO_ESCALATE(3, PWRMGR, 0)
+            OT_EG_SOC_GPIO_ESCALATE(3, PWRMGR, 0),
+            OT_EG_SOC_SIGNAL(OT_ALERT_NMI, 0, IBEX_WRAPPER, \
+                             OT_IBEX_WRAPPER_NMI, OT_IBEX_NMI_ALERT)
         ),
         .link = IBEXDEVICELINKDEFS(
             OT_EG_SOC_DEVLINK("edn", EDN0)

include/hw/opentitan/ot_alert.h

@@ -37,5 +37,6 @@ OBJECT_DECLARE_TYPE(OtAlertState, OtAlertStateClass, OT_ALERT)
 
 #define OT_DEVICE_ALERT   TYPE_OT_ALERT "-sig"
 #define OT_ALERT_ESCALATE TYPE_OT_ALERT "-esc"
+#define OT_ALERT_NMI      TYPE_OT_ALERT "-nmi"
 
 #endif /* HW_OPENTITAN_OT_ALERT_H */