RE: [PATCH net-next 5/5] net: mvpp2: jumbo frames support

[Stefan Chulski <stefanc@marvell.com>]

> > To perform checksum in HW, HW obviously should work in store and
> forward mode. Store all frame in TX FIFO and then check checksum.
> > If mtu 1500B, everything fine and all port can do this.
> >
> > If mtu is 9KB and 9KB frame transmitted, Port 0 still can do HW checksum.
> But ports 1 and 2 doesn't has enough FIFO for this.
> > So we cannot offload this feature and SW should perform checksum.
> 
> So perhaps the real check should not be "port 0", but whether the MTU is
> higher or lower than the TX FIFO size assigned to the current port.
> This would express in much better way the reason why HW checksum can be
> used or not.

I really don't want involve MTU size here, for each packet we should add to MTU overhead added by HW(offset, CRC, DSA tags and etc).
I prefer just to check: port TX FIFO size is 10KB -> port can support HW checksum offload.
Do you suggest to keep some shadow table with ports TX FIFO sizes for this?  

Thanks,
Stefan.