Re: [PATCH net v4 1/2] net: ethernet: bgmac: preserve forced 2.5 Gbps link speed

[Simon Horman]

On Thu, Oct 29, 2026 at 02:15:39PM -0700, Florian Fainelli wrote:
> 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@xxxxxxxxxxxx>

Reviewed-by: Simon Horman <horms@xxxxxxxxxx>