cadence_gem: fix interrupt events

Bits in the ISR were continually mirroring their corresponding TX/RX SR bits.
This is incorrect. The ISR bits are only ever set at the time their
corresponding event occurs.

Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Message-id: cedfb6d108318846480b416a6041023ea5a353d6.1360901435.git.peter.crosthwaite@xilinx.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/cadence_gem.c

diff --git a/hw/cadence_gem.c b/hw/cadence_gem.c
index 966ab4f..a1ac069 100644
--- a/hw/cadence_gem.c
+++ b/hw/cadence_gem.c
@@ -427,32 +427,9 @@
  */
 static void gem_update_int_status(GemState *s)
 {
-    uint32_t new_interrupts = 0;
-    /* Packet transmitted ? */
-    if (s->regs[GEM_TXSTATUS] & GEM_TXSTATUS_TXCMPL) {
-        new_interrupts |= GEM_INT_TXCMPL;
-    }
-    /* End of TX ring ? */
-    if (s->regs[GEM_TXSTATUS] & GEM_TXSTATUS_USED) {
-        new_interrupts |= GEM_INT_TXUSED;
-    }
-
-    /* Frame received ? */
-    if (s->regs[GEM_RXSTATUS] & GEM_RXSTATUS_FRMRCVD) {
-        new_interrupts |= GEM_INT_RXCMPL;
-    }
-    /* RX ring full ? */
-    if (s->regs[GEM_RXSTATUS] & GEM_RXSTATUS_NOBUF) {
-        new_interrupts |= GEM_INT_RXUSED;
-    }
-
-    s->regs[GEM_ISR] |= new_interrupts & ~(s->regs[GEM_IMR]);
-
     if (s->regs[GEM_ISR]) {
         DB_PRINT("asserting int. (0x%08x)\n", s->regs[GEM_ISR]);
         qemu_set_irq(s->irq, 1);
-    } else {
-        qemu_set_irq(s->irq, 0);
     }
 }
 
@@ -697,6 +674,7 @@
             DB_PRINT("descriptor 0x%x owned by sw.\n",
                      (unsigned)packet_desc_addr);
             s->regs[GEM_RXSTATUS] |= GEM_RXSTATUS_NOBUF;
+            s->regs[GEM_ISR] |= GEM_INT_RXUSED & ~(s->regs[GEM_IMR]);
             /* Handle interrupt consequences */
             gem_update_int_status(s);
             return -1;
@@ -765,6 +743,7 @@
                               (uint8_t *)&desc[0], sizeof(desc));
 
     s->regs[GEM_RXSTATUS] |= GEM_RXSTATUS_FRMRCVD;
+    s->regs[GEM_ISR] |= GEM_INT_RXCMPL & ~(s->regs[GEM_IMR]);
 
     /* Handle interrupt consequences */
     gem_update_int_status(s);
@@ -894,6 +873,7 @@
             DB_PRINT("TX descriptor next: 0x%08x\n", s->tx_desc_addr);
 
             s->regs[GEM_TXSTATUS] |= GEM_TXSTATUS_TXCMPL;
+            s->regs[GEM_ISR] |= GEM_INT_TXCMPL & ~(s->regs[GEM_IMR]);
 
             /* Handle interrupt consequences */
             gem_update_int_status(s);
@@ -931,6 +911,7 @@
 
     if (tx_desc_get_used(desc)) {
         s->regs[GEM_TXSTATUS] |= GEM_TXSTATUS_USED;
+        s->regs[GEM_ISR] |= GEM_INT_TXUSED & ~(s->regs[GEM_IMR]);
         gem_update_int_status(s);
     }
 }