[PATCH v5] net: stmmac: fix maxmtu assignment to be within valid range

["Kweh, Hock Leong" <hock.leong.kweh@intel.com>]

From: "Kweh, Hock Leong" <hock.leong.kweh@intel.com>

There is no checking valid value of maxmtu when getting it from
device tree. This resolution added the checking condition to
ensure the assignment is made within a valid range.

Signed-off-by: Kweh, Hock Leong <hock.leong.kweh@intel.com>
---
changelog v5:
* revert back that plat->maxmtu > ndev->max_mtu is a valid case
  when ndev->max_mtu assignment is entering to the else statement
* add comment to enchance clarification

changelog v4:
* add print warning message when maxmtu > max_mtu as well
* add maxmtu = JUMBO_LEN into each *_default_data() at stmmac_pci.c

changelog v3:
* print the warning message only if maxmtu < min_mtu
* add maxmtu = JUMBO_LEN at stmmac_pci.c to follow stmmac_platform.c

changelog v2:
* correction of "devicetree" to "device tree" reported by Andy
* print warning message while maxmtu is not in valid range

 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c |   10 +++++++++-
 drivers/net/ethernet/stmicro/stmmac/stmmac_pci.c  |    6 ++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 92ac006..8e56dc4 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -3345,8 +3345,16 @@ int stmmac_dvr_probe(struct device *device,
 		ndev->max_mtu = JUMBO_LEN;
 	else
 		ndev->max_mtu = SKB_MAX_HEAD(NET_SKB_PAD + NET_IP_ALIGN);
-	if (priv->plat->maxmtu < ndev->max_mtu)
+	/* Will not overwrite ndev->max_mtu if plat->maxmtu > ndev->max_mtu
+	 * as well as plat->maxmtu < ndev->min_mtu which is a invalid range.
+	 */
+	if ((priv->plat->maxmtu < ndev->max_mtu) &&
+	    (priv->plat->maxmtu >= ndev->min_mtu))
 		ndev->max_mtu = priv->plat->maxmtu;
+	else if (priv->plat->maxmtu < ndev->min_mtu)
+		netdev_warn(priv->dev,
+			    "%s: warning: maxmtu having invalid value (%d)\n",
+			    __func__, priv->plat->maxmtu);
 
 	if (flow_ctrl)
 		priv->flow_ctrl = FLOW_AUTO;	/* RX/TX pause on */
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_pci.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_pci.c
index a283177..3da4737 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_pci.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_pci.c
@@ -89,6 +89,9 @@ static void stmmac_default_data(struct plat_stmmacenet_data *plat)
 
 	/* Set default value for unicast filter entries */
 	plat->unicast_filter_entries = 1;
+
+	/* Set the maxmtu to a default of JUMBO_LEN */
+	plat->maxmtu = JUMBO_LEN;
 }
 
 static int quark_default_data(struct plat_stmmacenet_data *plat,
@@ -126,6 +129,9 @@ static int quark_default_data(struct plat_stmmacenet_data *plat,
 	/* Set default value for unicast filter entries */
 	plat->unicast_filter_entries = 1;
 
+	/* Set the maxmtu to a default of JUMBO_LEN */
+	plat->maxmtu = JUMBO_LEN;
+
 	return 0;
 }
 
-- 
1.7.9.5