There were several receive ring related bugs.

In velocity_give_many_rx_descs(), index calculation was incorrect.
This and bugs in velocity_rx_srv() described in the following paragraph
caused packet loss, truncation and infinite error interrupt generation.

In velocity_rx_srv(), velocity_rx_refill() could be called without any
dirty slot.  With proper timing, This can result in refilling yet
unreceived packets and pushing dirty pointer ahead of the current pointer.
And vptr->rd_curr which is used by velocity_rx_refill() was updated after
calling velocity_rx_refill() thus screwing receive descriptor ring.
Also, between checking owner and reading the packet, rmb() is missing.
Signed-off-by: Tejun Heo <tj@home-tj.org>