RE : [PATCH 3/4 V2] Add for MCF54xx a virtual non cached zone usable for data exchange with DMA

Stany MARCEL
2012-10-16T13:52:58Z

Hi Greg,

For Informations, here are some measurements I can remember of
different solutions I have tested, measurements where done with iperf
in TCP and UDP :

- Copyback cache without flush: ~40Mbits/sec in TCP but UDP tests
shows a lot of lost frames.

- Copyback cache with full data flush : ~9Mbits/sec in TCP, don't
remember in UDP.

- DMA_ZONE : ~32Mbits/sec, UDP ok.

These results are very approximative, if I can I'll try to give you
more precise tests results.

For the partitioning and used TLB entries, with default settings I map
8MiB with 8TLB entry (on 32).

I choose this path as it is recommended by the documentation and I
also saw that it was the solution used by Freescale, on their old
Linux patch.

I agree that cache managing functions should also be improved. But
with available cache management possibility on mcf54xx mcu, I don't
see how to perform effectively the operations needed to exchange data
with built-in DMA.

So for my project I will live with this solution for the moment.

Regards,

--
Stany