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

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@cogentembedded.com>
---

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