[PATCH] net: stmmac:fix system hang when setting up tag_8021q VLAN for DSA ports

[Yan Wang]

The system hang because of dsa_tag_8021q_port_setup()->
				stmmac_vlan_rx_add_vid().

I found in stmmac_drv_probe() that cailing pm_runtime_put()
disabled the clock.

First, when the kernel is compiled with CONFIG_PM=y,The stmmac's
resume/suspend is active.

Secondly,stmmac as DSA master,the dsa_tag_8021q_port_setup() function
will callback stmmac_vlan_rx_add_vid when DSA dirver starts. However,
The system is hanged for the stmmac_vlan_rx_add_vid() accesses its
registers after stmmac's clock is closed.

I would suggest adding the pm_runtime_resume_and_get() to the
stmmac_vlan_rx_add_vid().This guarantees that resuming clock output
while in use.

Signed-off-by: Yan Wang <rk.code@xxxxxxxxxxx>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index d7fcab057032..f9cd063f1fe3 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -6350,6 +6350,10 @@ static int stmmac_vlan_rx_add_vid(struct net_device *ndev, __be16 proto, u16 vid
 	bool is_double = false;
 	int ret;
 
+	ret = pm_runtime_resume_and_get(priv->device);
+	if (ret < 0)
+		return ret;
+
 	if (be16_to_cpu(proto) == ETH_P_8021AD)
 		is_double = true;
 
@@ -6357,16 +6361,18 @@ static int stmmac_vlan_rx_add_vid(struct net_device *ndev, __be16 proto, u16 vid
 	ret = stmmac_vlan_update(priv, is_double);
 	if (ret) {
 		clear_bit(vid, priv->active_vlans);
-		return ret;
+		goto err_pm_put;
 	}
 
 	if (priv->hw->num_vlan) {
 		ret = stmmac_add_hw_vlan_rx_fltr(priv, ndev, priv->hw, proto, vid);
 		if (ret)
-			return ret;
+			goto err_pm_put;
 	}
+err_pm_put:
+	pm_runtime_put(priv->device);
 
-	return 0;
+	return ret;
 }
 
 static int stmmac_vlan_rx_kill_vid(struct net_device *ndev, __be16 proto, u16 vid)
-- 
2.17.1