From e03664867aa0ef308c38f4953910498eaaa2afee Mon Sep 17 00:00:00 2001
From: Robert Marko <robert.marko@sartura.hr>
Date: Fri, 19 Nov 2021 03:03:50 +0100
Subject: [PATCH 3/8] net: dsa: qca8k: fix MTU calculation
Git-commit: 65258b9d8cde45689bdc86ca39b50f01f983733b
Patch-mainline: v5.16-rc3
References: git-fixes
qca8k has a global MTU, so its tracking the MTU per port to make sure
that the largest MTU gets applied.
Since it uses the frame size instead of MTU the driver MTU change function
will then add the size of Ethernet header and checksum on top of MTU.
The driver currently populates the per port MTU size as Ethernet frame
length + checksum which equals 1518.
The issue is that then MTU change function will go through all of the
ports, find the largest MTU and apply the Ethernet header + checksum on
top of it again, so for a desired MTU of 1500 you will end up with 1536.
This is obviously incorrect, so to correct it populate the per port struct
MTU with just the MTU and not include the Ethernet header + checksum size
as those will be added by the MTU change function.
Fixes: f58d2598cf70 ("net: dsa: qca8k: implement the port MTU callbacks")
Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Denis Kirjanov <denis.kirjanov@suse.com>
---
drivers/net/dsa/qca8k.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c
index a984f06f6f04..d96f5d7473a3 100644
--- a/drivers/net/dsa/qca8k.c
+++ b/drivers/net/dsa/qca8k.c
@@ -1122,7 +1122,7 @@ qca8k_setup(struct dsa_switch *ds)
/* Setup our port MTUs to match power on defaults */
for (i = 0; i < QCA8K_NUM_PORTS; i++)
- priv->port_mtu[i] = ETH_FRAME_LEN + ETH_FCS_LEN;
+ priv->port_mtu[i] = ETH_DATA_LEN;
ret = qca8k_write(priv, QCA8K_MAX_FRAME_SIZE, ETH_FRAME_LEN + ETH_FCS_LEN);
if (ret)
dev_warn(priv->dev, "failed setting MTU settings");
--
2.16.4