[PATCH net v2] net: systemport: Correct IPG length settings

[PATCH net v2] net: systemport: Correct IPG length settings

[Florian Fainelli]

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>
---
Changes in v2:

- move the IPG length setting outside of netdev_uses_dsa() branch

 drivers/net/ethernet/broadcom/bcmsysport.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bcmsysport.c b/drivers/net/ethernet/broadcom/bcmsysport.c
index 83eec9a8c275..eb441e5e2cd8 100644
--- a/drivers/net/ethernet/broadcom/bcmsysport.c
+++ b/drivers/net/ethernet/broadcom/bcmsysport.c
@@ -1809,15 +1809,17 @@ static inline void bcm_sysport_mask_all_intrs(struct bcm_sysport_priv *priv)
 
 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)
-- 
2.9.3

Re: [PATCH net v2] net: systemport: Correct IPG length settings

[David Miller]

From: Florian Fainelli <f.fainelli@gmail.com>
Date: Thu,  2 Nov 2017 16:08:40 -0700

> 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>

Applied and queued up for -stable.