ahci: Force ICC bits in PxCMD to zero

The AHCI spec requires that the HBA sets the ICC bits to zero after the
ICC change is done. Since we don't do any ICC change, force the bits to
zero all the time.

This fixes delays with some OSs (e.g. OpenBSD) waiting for the ICC bits
to change to 0.
Signed-off-by: NStefan Fritsch <sf@sfritsch.de>
Reviewed-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NJohn Snow <jsnow@redhat.com>
Message-id: E1ZFpg7-00027N-HW@eru.sfritsch.de
Signed-off-by: NJohn Snow <jsnow@redhat.com>

hw/ide/ahci.c

@@ -279,8 +279,13 @@ static void  ahci_port_write(AHCIState *s, int port, int offset, uint32_t val)
             break;
         case PORT_CMD:
             /* Block any Read-only fields from being set;
-             * including LIST_ON and FIS_ON. */
-            pr->cmd = (pr->cmd & PORT_CMD_RO_MASK) | (val & ~PORT_CMD_RO_MASK);
+             * including LIST_ON and FIS_ON.
+             * The spec requires to set ICC bits to zero after the ICC change
+             * is done. We don't support ICC state changes, therefore always
+             * force the ICC bits to zero.
+             */
+            pr->cmd = (pr->cmd & PORT_CMD_RO_MASK) |
+                      (val & ~(PORT_CMD_RO_MASK|PORT_CMD_ICC_MASK));
 
             /* Check FIS RX and CLB engines, allow transition to false: */
             ahci_cond_start_engines(&s->dev[port], true);