On Wednesday 01 March 2006 14:23, Joyeau Sylvain wrote: > Hi, > > Does anybody already succeeded in getting full TX bandwidth on a TSEC > interface, transmitting 1500 bytes frames at netdev level (ie calling > directly dev_queue_xmit(skb)) for instance ? > > With default Gianfar driver parameters, I can transmit only around > 870Mb/s (while reception side is idle). The other TSEC interface is used > only to control a telnet terminal (~1Kb/s), the CPU is idle 60%, > 6000irq/s. > > I must decrease TX threshold value from 1024 to 128 to get 960Mb/s. > > The problem is that decreasing the TX threshold under 512 bytes has a > dramatic side effect: the Gianfar driver generates "TX underrun" events > as soon as I start, in parallel, a DMA transfer from memory to memory. > Rather disappointing behavior from a PQ3 at 825MHz :-( > > Any idea how to get full TX bandwidth _without_ modifying this > parameter? > > Thanks. > > -- > sylvain >
I don't know 85xx in any great detail, but most QUICCs have a register that controls the DMA bus arbitration priorities. Find it and give the highest priority to the ethernet. Pantelis
