RE: [PATCH net-next v2 0/2] Enable 2.5Gbps speed for stmmac

quoted

The limitation is not on the MAC, PCS or the PHY. For Intel mgbe, the
overclocking of 2.5 times clock rate to support 2.5G is only able to
be configured in the BIOS during boot time. Kernel driver has no
access to modify the clock rate for 1Gbps/2.5G mode. The way to
determined the current 1G/2.5G mode is by reading a dedicated adhoc

register through mdio bus.

quoted

In short, after the system boot up, it is either in 1G mode or 2.5G
mode which not able to be changed on the fly.

Right. It would of been a lot easier if this was in the commit message
from the beginning. Please ensure the next version does say this.

quoted

Since the stmmac MAC can pair with any PCS and PHY, I still prefer
that we tie this platform specific limitation with the of MAC. As
stmmac does handle platform specific config/limitation.

So yes, this needs to be somewhere in the intel specific stmmac code,
with a nice comment explaining what is going on.

What PHY are you using? The Aquantia/Marvell multi-gige phy can do rate
adaptation. So you could fix the MAC-PHY link to 2500BaseX, and let the
PHY internally handle the different line speeds.

Intel mgbe is flexible to pair with any PHY. Only Aquantia/Marvell
multi-gige PHY can do rate adaption right? Hence, we still need to take 
care of others PHYs.

Thanks for all the comments, will include them in v3. 

Weifeng