linux-kernel - [PATCH 7/7] dsa: marvell: Modify get max MTU callback to use per switch provided value

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Date:   Thu,  9 Mar 2023 13:54:21 +0100
From:   Lukasz Majewski <lukma@...x.de>
To:     Andrew Lunn <andrew@...n.ch>, Vladimir Oltean <olteanv@...il.com>,
        Russell King <linux@...linux.org.uk>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lukasz Majewski <lukma@...x.de>
Subject: [PATCH 7/7] dsa: marvell: Modify get max MTU callback to use per switch provided value

After this change the value specified in max_frame_size variable is used
to provide information regarding the maximal size of frame supported in
the switch.

This approach replaces the current detection scheme, which extracts
information about max frame size depending on set of provided callbacks.

This is wrong, as some switch ICs can have max frame size equal to 1632
or 2048 and both would provide set_max_frame_size callback.

Signed-off-by: Lukasz Majewski <lukma@...x.de>
---
Changes for v5:
- New patch
---
 drivers/net/dsa/mv88e6xxx/chip.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
index dbb69787f4ef..6a5acbba381e 100644
--- a/drivers/net/dsa/mv88e6xxx/chip.c
+++ b/drivers/net/dsa/mv88e6xxx/chip.c
@@ -3545,11 +3545,10 @@ static int mv88e6xxx_get_max_mtu(struct dsa_switch *ds, int port)
 {
 	struct mv88e6xxx_chip *chip = ds->priv;
 
-	if (chip->info->ops->port_set_jumbo_size)
-		return 10240 - VLAN_ETH_HLEN - EDSA_HLEN - ETH_FCS_LEN;
-	else if (chip->info->ops->set_max_frame_size)
-		return 1632 - VLAN_ETH_HLEN - EDSA_HLEN - ETH_FCS_LEN;
-	return 1522 - VLAN_ETH_HLEN - EDSA_HLEN - ETH_FCS_LEN;
+	WARN_ON_ONCE(!chip->info->max_frame_size);
+
+	return chip->info->max_frame_size - VLAN_ETH_HLEN - EDSA_HLEN
+	       - ETH_FCS_LEN;
 }
 
 static int mv88e6xxx_change_mtu(struct dsa_switch *ds, int port, int new_mtu)
-- 
2.20.1