net: hns: fix fake link up on xge port

If a xge port just connect with an optical module and no fiber,
it may have a fake link up because there may be interference on
the hardware. This patch adds an anti-shake to avoid the problem.
And the time of anti-shake is base on tests.

Fixes: b917078c ("net: hns: Add ACPI support to check SFP present")
Signed-off-by: Yonglong Liu <liuyonglong@huawei.com>
Signed-off-by: Jijie Shao <shaojijie@huawei.com>
Reviewed-by: Wojciech Drewek <wojciech.drewek@intel.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/hisilicon/hns/hns_dsaf_mac.c

@@ -66,6 +66,27 @@ static enum mac_mode hns_get_enet_interface(const struct hns_mac_cb *mac_cb)
 	}
 }
 
+static u32 hns_mac_link_anti_shake(struct mac_driver *mac_ctrl_drv)
+{
+#define HNS_MAC_LINK_WAIT_TIME 5
+#define HNS_MAC_LINK_WAIT_CNT 40
+
+	u32 link_status = 0;
+	int i;
+
+	if (!mac_ctrl_drv->get_link_status)
+		return link_status;
+
+	for (i = 0; i < HNS_MAC_LINK_WAIT_CNT; i++) {
+		msleep(HNS_MAC_LINK_WAIT_TIME);
+		mac_ctrl_drv->get_link_status(mac_ctrl_drv, &link_status);
+		if (!link_status)
+			break;
+	}
+
+	return link_status;
+}
+
 void hns_mac_get_link_status(struct hns_mac_cb *mac_cb, u32 *link_status)
 {
 	struct mac_driver *mac_ctrl_drv;
@@ -83,6 +104,14 @@ void hns_mac_get_link_status(struct hns_mac_cb *mac_cb, u32 *link_status)
 							       &sfp_prsnt);
 		if (!ret)
 			*link_status = *link_status && sfp_prsnt;
+
+		/* for FIBER port, it may have a fake link up.
+		 * when the link status changes from down to up, we need to do
+		 * anti-shake. the anti-shake time is base on tests.
+		 * only FIBER port need to do this.
+		 */
+		if (*link_status && !mac_cb->link)
+			*link_status = hns_mac_link_anti_shake(mac_ctrl_drv);
 	}
 
 	mac_cb->link = *link_status;