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47 lines
2.0 KiB
Diff
47 lines
2.0 KiB
Diff
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From 65258b9d8cde45689bdc86ca39b50f01f983733b Mon Sep 17 00:00:00 2001
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From: Robert Marko <robert.marko@sartura.hr>
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Date: Fri, 19 Nov 2021 03:03:50 +0100
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Subject: [PATCH] net: dsa: qca8k: fix MTU calculation
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qca8k has a global MTU, so its tracking the MTU per port to make sure
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that the largest MTU gets applied.
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Since it uses the frame size instead of MTU the driver MTU change function
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will then add the size of Ethernet header and checksum on top of MTU.
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The driver currently populates the per port MTU size as Ethernet frame
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length + checksum which equals 1518.
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The issue is that then MTU change function will go through all of the
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ports, find the largest MTU and apply the Ethernet header + checksum on
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top of it again, so for a desired MTU of 1500 you will end up with 1536.
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This is obviously incorrect, so to correct it populate the per port struct
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MTU with just the MTU and not include the Ethernet header + checksum size
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as those will be added by the MTU change function.
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Fixes: f58d2598cf70 ("net: dsa: qca8k: implement the port MTU callbacks")
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Signed-off-by: Robert Marko <robert.marko@sartura.hr>
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Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
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Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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drivers/net/dsa/qca8k.c | 6 +++++-
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1 file changed, 5 insertions(+), 1 deletion(-)
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--- a/drivers/net/dsa/qca8k.c
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+++ b/drivers/net/dsa/qca8k.c
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@@ -1256,8 +1256,12 @@ qca8k_setup(struct dsa_switch *ds)
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/* Set initial MTU for every port.
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* We have only have a general MTU setting. So track
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* every port and set the max across all port.
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+ * Set per port MTU to 1500 as the MTU change function
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+ * will add the overhead and if its set to 1518 then it
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+ * will apply the overhead again and we will end up with
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+ * MTU of 1536 instead of 1518
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*/
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- priv->port_mtu[i] = ETH_FRAME_LEN + ETH_FCS_LEN;
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+ priv->port_mtu[i] = ETH_DATA_LEN;
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}
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/* Special GLOBAL_FC_THRESH value are needed for ar8327 switch */
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