hw/intc: ibex_plic: Don't allow repeat interrupts on claimed lines

Once an interrupt has been claimed, but before it has been compelted we
shouldn't receive any more pending interrupts. This patche keeps track
of this to ensure that we don't see any more interrupts until it is
completed.

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <394c3f070615ff2b4fab61a1cf9cb48c122913b7.1595655188.git.alistair.francis@wdc.com>

hw/intc/ibex_plic.c

@@ -43,6 +43,14 @@ static void ibex_plic_irqs_set_pending(IbexPlicState *s, int irq, bool level)
 {
     int pending_num = irq / 32;
 
+    if (s->claimed[pending_num] & 1 << (irq % 32)) {
+        /*
+         * The interrupt has been claimed, but not compelted.
+         * The pending bit can't be set.
+         */
+        return;
+    }
+
     s->pending[pending_num] |= level << (irq % 32);
 }
 
@@ -120,6 +128,10 @@ static uint64_t ibex_plic_read(void *opaque, hwaddr addr,
         int pending_num = s->claim / 32;
         s->pending[pending_num] &= ~(1 << (s->claim % 32));
 
+        /* Set the interrupt as claimed, but not compelted */
+        s->claimed[pending_num] |= 1 << (s->claim % 32);
+
+        /* Return the current claimed interrupt */
         ret = s->claim;
 
         /* Update the interrupt status after the claim */
@@ -155,6 +167,10 @@ static void ibex_plic_write(void *opaque, hwaddr addr,
             /* Interrupt was completed */
             s->claim = 0;
         }
+        if (s->claimed[value / 32] & 1 << (value % 32)) {
+            /* This value was already claimed, clear it. */
+            s->claimed[value / 32] &= ~(1 << (value % 32));
+        }
     }
 
     ibex_plic_update(s);
@@ -215,6 +231,7 @@ static void ibex_plic_realize(DeviceState *dev, Error **errp)
     int i;
 
     s->pending = g_new0(uint32_t, s->pending_num);
+    s->claimed = g_new0(uint32_t, s->pending_num);
     s->source = g_new0(uint32_t, s->source_num);
     s->priority = g_new0(uint32_t, s->priority_num);
     s->enable = g_new0(uint32_t, s->enable_num);

include/hw/intc/ibex_plic.h

@@ -33,6 +33,7 @@ typedef struct IbexPlicState {
     MemoryRegion mmio;
 
     uint32_t *pending;
+    uint32_t *claimed;
     uint32_t *source;
     uint32_t *priority;
     uint32_t *enable;