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linux/drivers/net/dsa
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Vladimir Oltean 7e9517375a net: dsa: mv88e6xxx: fix max_mtu of 1492 on 6165, 6191, 6220, 6250, 6290 
There are 3 classes of switch families that the driver is aware of, as
far as mv88e6xxx_change_mtu() is concerned:

- MTU configuration is available per port. Here, the
  chip->info->ops->port_set_jumbo_size() method will be present.

- MTU configuration is global to the switch. Here, the
  chip->info->ops->set_max_frame_size() method will be present.

- We don't know how to change the MTU. Here, none of the above methods
  will be present.

Switch families MV88E6165, MV88E6191, MV88E6220, MV88E6250 and MV88E6290
fall in category 3.

The blamed commit has adjusted the MTU for all 3 categories by EDSA_HLEN
(8 bytes), resulting in a new maximum MTU of 1492 being reported by the
driver for these switches.

I don't have the hardware to test, but I do have a MV88E6390 switch on
which I can simulate this by commenting out its .port_set_jumbo_size
definition from mv88e6390_ops. The result is this set of messages at
probe time:

mv88e6085 d0032004.mdio-mii:10: nonfatal error -34 setting MTU to 1500 on port 1
mv88e6085 d0032004.mdio-mii:10: nonfatal error -34 setting MTU to 1500 on port 2
mv88e6085 d0032004.mdio-mii:10: nonfatal error -34 setting MTU to 1500 on port 3
mv88e6085 d0032004.mdio-mii:10: nonfatal error -34 setting MTU to 1500 on port 4
mv88e6085 d0032004.mdio-mii:10: nonfatal error -34 setting MTU to 1500 on port 5
mv88e6085 d0032004.mdio-mii:10: nonfatal error -34 setting MTU to 1500 on port 6
mv88e6085 d0032004.mdio-mii:10: nonfatal error -34 setting MTU to 1500 on port 7
mv88e6085 d0032004.mdio-mii:10: nonfatal error -34 setting MTU to 1500 on port 8

It is highly implausible that there exist Ethernet switches which don't
support the standard MTU of 1500 octets, and this is what the DSA
framework says as well - the error comes from dsa_slave_create() ->
dsa_slave_change_mtu(slave_dev, ETH_DATA_LEN).

But the error messages are alarming, and it would be good to suppress
them.

As a consequence of this unlikeliness, we reimplement mv88e6xxx_get_max_mtu()
and mv88e6xxx_change_mtu() on switches from the 3rd category as follows:
the maximum supported MTU is 1500, and any request to set the MTU to a
value larger than that fails in dev_validate_mtu().

Fixes: b9c587fed6 ("dsa: mv88e6xxx: Include tagger overhead when setting MTU for DSA and CPU ports")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2023-03-16 17:39:42 +00:00
..
b53 net: dsa: modularize DSA_TAG_PROTO_NONE 2022-11-22 20:41:45 -08:00
hirschmann net: devlink: let the core report the driver name instead of the drivers 2022-11-30 21:49:38 -08:00
microchip net: dsa: microchip: enable EEE support 2023-02-13 11:12:31 +00:00
mv88e6xxx net: dsa: mv88e6xxx: fix max_mtu of 1492 on 6165, 6191, 6220, 6250, 6290 2023-03-16 17:39:42 +00:00
ocelot net: dsa: ocelot_ext: remove unnecessary phylink.h include 2023-02-26 18:41:33 +00:00
qca net: dsa: qca8k: convert to regmap read/write API 2023-01-27 12:06:45 +00:00
realtek
sja1105 net: Remove C45 check in C22 only MDIO bus drivers 2023-01-20 18:12:45 -08:00
xrs700x net: dsa: xrs700x: Convert to i2c's .probe_new() 2022-11-23 12:50:06 -08:00
bcm_sf2.c
bcm_sf2.h
bcm_sf2_cfp.c
bcm_sf2_regs.h
dsa_loop.c net: dsa: Fix possible memory leaks in dsa_loop_init() 2022-10-28 10:32:59 +01:00
dsa_loop.h
dsa_loop_bdinfo.c
Kconfig net: dsa: mt7530: fix tristate and help description 2023-01-27 22:33:49 -08:00
lan9303-core.c dsa: lan9303: Add flow ctrl in link_up 2023-01-20 08:53:13 +00:00
lan9303.h
lan9303_i2c.c net: dsa: lan9303: Convert to i2c's .probe_new() 2022-11-23 12:50:05 -08:00
lan9303_mdio.c
lantiq_gswip.c
lantiq_pce.h
Makefile
mt7530.c net: dsa: mt7530: set PLL frequency and trgmii only when trgmii is used 2023-03-13 17:04:18 -07:00
mt7530.h net: dsa: mt7530: Separate C22 and C45 MDIO bus transactions 2023-01-17 19:34:07 -08:00
mv88e6060.c
mv88e6060.h
rzn1_a5psw.c net: Remove C45 check in C22 only MDIO bus drivers 2023-01-20 18:12:45 -08:00
rzn1_a5psw.h
vitesse-vsc73xx-core.c
vitesse-vsc73xx-platform.c
vitesse-vsc73xx-spi.c
vitesse-vsc73xx.h