net: ethernet: bgmac: preserve forced 2.5 Gbps link speed

Northstar and Northstar Plus use a 2.5 Gbps internal link between the
AMAC and the switch.  BGMAC_FEAT_FORCE_SPEED_2500 makes bgmac_miiconfig()
configure that speed, but bgmac_adjust_link() subsequently replaces it
with the synthetic fixed PHY's 1 Gbps speed.

Use the forced speed when processing link changes so the MAC remains at
2.5 Gbps.  Together with configuring the switch IMP port for its 2 Gbps
mode, this eliminates the output queue discards that caused approximately
1000 TCP retransmissions per second during an iperf3 transmit test.

Restrict the platform forced-speed flag to Northstar Plus using the SoC
compatible, since Hurricane2 shares the AMAC compatible. Other platform
AMACs without a phy-handle must continue following the fixed PHY speed.
The BCMA path already selects the flag only for the Northstar family.

Fixes: f6a95a24957a ("net: ethernet: bgmac: Add platform device support")
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20261029211540.4123250-2-florian.fainelli@broadcom.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

0 files changed, 0 insertions, 0 deletions