stmmac: Don't init ptp again when resume from suspend/hibernation

Both stmmac_open() and stmmac_resume() call stmmac_hw_setup(), and
stmmac_hw_setup() call stmmac_init_ptp() unconditionally. However, only
stmmac_release() calls stmmac_release_ptp(). Since stmmac_suspend()
doesn't call stmmac_release_ptp(), stmmac_resume() also needn't call
stmmac_init_ptp().

This patch also fix a "scheduling while atomic" problem when resume
from suspend/hibernation. Because stmmac_init_ptp() will trigger
scheduling while stmmac_resume() hold a spinlock.

Callgraph of "scheduling while atomic":
stmmac_resume() --> stmmac_hw_setup() --> stmmac_init_ptp() -->
stmmac_ptp_register() --> ptp_clock_register() --> device_create() -->
device_create_groups_vargs() --> device_add() --> devtmpfs_create_node()
--> wait_for_common() --> schedule_timeout() --> __schedule()
Signed-off-by: Huacai Chen <chenhc@lemote.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -1671,7 +1671,7 @@ static void stmmac_init_tx_coalesce(struct stmmac_priv *priv)
  *  0 on success and an appropriate (-)ve integer as defined in errno.h
  *  file on failure.
  */
-static int stmmac_hw_setup(struct net_device *dev)
+static int stmmac_hw_setup(struct net_device *dev, bool init_ptp)
 {
 	struct stmmac_priv *priv = netdev_priv(dev);
 	int ret;
@@ -1708,9 +1708,11 @@ static int stmmac_hw_setup(struct net_device *dev)
 
 	stmmac_mmc_setup(priv);
 
-	ret = stmmac_init_ptp(priv);
-	if (ret && ret != -EOPNOTSUPP)
-		pr_warn("%s: failed PTP initialisation\n", __func__);
+	if (init_ptp) {
+		ret = stmmac_init_ptp(priv);
+		if (ret && ret != -EOPNOTSUPP)
+			pr_warn("%s: failed PTP initialisation\n", __func__);
+	}
 
 #ifdef CONFIG_DEBUG_FS
 	ret = stmmac_init_fs(dev);
@@ -1787,7 +1789,7 @@ static int stmmac_open(struct net_device *dev)
 		goto init_error;
 	}
 
-	ret = stmmac_hw_setup(dev);
+	ret = stmmac_hw_setup(dev, true);
 	if (ret < 0) {
 		pr_err("%s: Hw setup failed\n", __func__);
 		goto init_error;
@@ -3036,7 +3038,7 @@ int stmmac_resume(struct net_device *ndev)
 	netif_device_attach(ndev);
 
 	init_dma_desc_rings(ndev, GFP_ATOMIC);
-	stmmac_hw_setup(ndev);
+	stmmac_hw_setup(ndev, false);
 	stmmac_init_tx_coalesce(priv);
 
 	napi_enable(&priv->napi);