net: airoha_eth: increase max MTU to 9220 for DSA jumbo frames

The industry standard jumbo frame MTU is 9216 bytes. When using the DSA
subsystem, a 4-byte tag is added to each Ethernet frame.

Increase AIROHA_MAX_MTU to 9220 bytes (9216 + 4) so that users can set a
standard 9216-byte MTU on DSA ports.

The underlying hardware supports significantly larger frame sizes
(approximately 16K). However, the maximum MTU is limited to 9220 bytes
for now, as this is sufficient to support standard jumbo frames and does
not incur additional memory allocation overhead.

Signed-off-by: Sayantan Nandy <sayantann11@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://patch.msgid.link/20260119073658.6216-1-sayantann11@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/airoha/airoha_eth.h b/drivers/net/ethernet/airoha/airoha_eth.h
index fbbc58133364baefafed30299ca0626c686b668e..20e602d61e615e0cf73ac7125bee85ff98986229 100644 (file)
--- a/drivers/net/ethernet/airoha/airoha_eth.h
+++ b/drivers/net/ethernet/airoha/airoha_eth.h
@@ -21,7 +21,7 @@
 #define AIROHA_MAX_NUM_IRQ_BANKS       4
 #define AIROHA_MAX_DSA_PORTS           7
 #define AIROHA_MAX_NUM_RSTS            3
-#define AIROHA_MAX_MTU                 9216
+#define AIROHA_MAX_MTU                 9220
 #define AIROHA_MAX_PACKET_SIZE         2048
 #define AIROHA_NUM_QOS_CHANNELS                4
 #define AIROHA_NUM_QOS_QUEUES          8