From: Florian Fainelli <f.fainelli@gmail.com>
Date: Thu, 2 Nov 2017 16:08:40 -0700
Subject: net: systemport: Correct IPG length settings
Git-commit: 93824c80bf47ebe087414b3a40ca0ff9aab7d1fb
Patch-mainline: v4.14-rc8
References: networking-stable-17_11_20

Due to a documentation mistake, the IPG length was set to 0x12 while it
should have been 12 (decimal). This would affect short packet (64B
typically) performance since the IPG was bigger than necessary.

Fixes: 44a4524c54af ("net: systemport: Add support for SYSTEMPORT Lite")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/net/ethernet/broadcom/bcmsysport.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/drivers/net/ethernet/broadcom/bcmsysport.c
+++ b/drivers/net/ethernet/broadcom/bcmsysport.c
@@ -1739,15 +1739,17 @@ static inline void bcm_sysport_mask_all_
 
 static inline void gib_set_pad_extension(struct bcm_sysport_priv *priv)
 {
-	u32 __maybe_unused reg;
+	u32 reg;
 
-	/* Include Broadcom tag in pad extension */
+	reg = gib_readl(priv, GIB_CONTROL);
+	/* Include Broadcom tag in pad extension and fix up IPG_LENGTH */
 	if (netdev_uses_dsa(priv->netdev)) {
-		reg = gib_readl(priv, GIB_CONTROL);
 		reg &= ~(GIB_PAD_EXTENSION_MASK << GIB_PAD_EXTENSION_SHIFT);
 		reg |= ENET_BRCM_TAG_LEN << GIB_PAD_EXTENSION_SHIFT;
-		gib_writel(priv, reg, GIB_CONTROL);
 	}
+	reg &= ~(GIB_IPG_LEN_MASK << GIB_IPG_LEN_SHIFT);
+	reg |= 12 << GIB_IPG_LEN_SHIFT;
+	gib_writel(priv, reg, GIB_CONTROL);
 }
 
 static int bcm_sysport_open(struct net_device *dev)