Re: [patch net / RFC] net: fec: increase frame size limitation to actually available buffer

[Zefir Kurtisi]

On 11/29/2016 07:35 PM, Nikita Yushchenko wrote:
> Fec driver uses Rx buffers of 2k, but programs hardware to limit
> incoming frames to 1522 bytes. This raises issues when FEC device
> is used with DSA (since DSA tag can make frame larger), and also
> disallows manual sending and receiving larger frames.
> 
> This patch removes the limitation, allowing Rx size up to entire buffer.
> At the same time possible Tx size is increased as well, because hardware
> uses the same register field to limit Rx and Tx.
> 
> Signed-off-by: Nikita Yushchenko <nikita.yoush@xxxxxxxxxxxxxxxxxx>
> ---

I recently did similar changes to the freescale/gianfar to prevent fragmentation
of (E)DSA frames [1].

With the fragmentation kicking in, I noticed a bug in the scatter-gather logic
which caused the frame-size of fragmented frames to be reported wrong [2]. Not
sure if the fec driver has SG capabilities and if this issue also applies, you
might want to double-check.


Cheers,
Zefir


[1] http://marc.info/?l=linux-netdev&m=147187438313519&w=2
[2] http://marc.info/?l=linux-netdev&m=147187430213484&w=2