NTB: add support for hotplug feature

AMD NTB support hotplug under B2B mode. NTB will trigger link
up/down interrupt event when doing plug add/remove, this patch
implements the two interrupt event to support B2B hotplug function.
Signed-off-by: Xiangliang Yu <Xiangliang.Yu@amd.com>
Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Acked-by: Allen Hubbe <Allen.Hubbe@dell.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>

drivers/ntb/hw/amd/ntb_hw_amd.c

@@ -199,6 +199,11 @@ static int amd_link_is_up(struct amd_ntb_dev *ndev)
 	if (!ndev->peer_sta)
 		return NTB_LNK_STA_ACTIVE(ndev->cntl_sta);
 
+	if (ndev->peer_sta & AMD_LINK_UP_EVENT) {
+		ndev->peer_sta = 0;
+		return 1;
+	}
+
 	/* If peer_sta is reset or D0 event, the ISR has
 	 * started a timer to check link status of hardware.
 	 * So here just clear status bit. And if peer_sta is
@@ -207,7 +212,7 @@ static int amd_link_is_up(struct amd_ntb_dev *ndev)
 	 */
 	if (ndev->peer_sta & AMD_PEER_RESET_EVENT)
 		ndev->peer_sta &= ~AMD_PEER_RESET_EVENT;
-	else if (ndev->peer_sta & AMD_PEER_D0_EVENT)
+	else if (ndev->peer_sta & (AMD_PEER_D0_EVENT | AMD_LINK_DOWN_EVENT))
 		ndev->peer_sta = 0;
 
 	return 0;
@@ -491,6 +496,8 @@ static void amd_handle_event(struct amd_ntb_dev *ndev, int vec)
 		break;
 	case AMD_PEER_D3_EVENT:
 	case AMD_PEER_PMETO_EVENT:
+	case AMD_LINK_UP_EVENT:
+	case AMD_LINK_DOWN_EVENT:
 		amd_ack_smu(ndev, status);
 
 		/* link down */

drivers/ntb/hw/amd/ntb_hw_amd.h

@@ -148,9 +148,12 @@ enum {
 	AMD_PEER_D3_EVENT	= BIT(2),
 	AMD_PEER_PMETO_EVENT	= BIT(3),
 	AMD_PEER_D0_EVENT	= BIT(4),
+	AMD_LINK_UP_EVENT	= BIT(5),
+	AMD_LINK_DOWN_EVENT	= BIT(6),
 	AMD_EVENT_INTMASK	= (AMD_PEER_FLUSH_EVENT |
 				AMD_PEER_RESET_EVENT | AMD_PEER_D3_EVENT |
-				AMD_PEER_PMETO_EVENT | AMD_PEER_D0_EVENT),
+				AMD_PEER_PMETO_EVENT | AMD_PEER_D0_EVENT |
+				AMD_LINK_UP_EVENT | AMD_LINK_DOWN_EVENT),
 
 	AMD_PMESTAT_OFFSET	= 0x480,
 	AMD_PMSGTRIG_OFFSET	= 0x490,