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After looking over the OFDM reference design provided, I noticed that the ethernet is set to polling mode.
Since EMAC has interrupt features, is there any particular reason it is not used?
Wouldn't it be faster and more efficient to do that?
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In the current reference designs, the OFDM core is attached to the OPB. With this setup, we found that the time required to copy packets over the OPB dominates the total per-packet processing time. The current designs also use Xilkernel, which wraps interrupt handling in its own (poorly documented) interrupt framework. Given these issues, we decided to simplify the overall code and use the Ethernet MAC's polled mode.
We're nearly finished with a new reference design that fixes all of these issues. The OFDM core's packet buffers are now attached to the PLB, Xilkernel is no longer used and the Ethernet MAC is used in interrupt/simple DMA mode. As you might expect, the performance is significantly improved with this setup.
The updated version of WARPMAC is already available in the repository. We're still fixing a few bugs in the code and hope to post the full, updated reference design by next week.
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This is really the way to go! Terry is also working on etherne_EMAC IP using interrupt and DMA. However, we were also confused by Xilkernel. We also plan to reduce the complexity of interrupt handler and transfer most functional load into main().
(1) If Xilkernel is no long used, which OS is used for the new reference design? I browsed through the WARPMAC.c and it Looks like standalone, right?
(2) Any tutorial note you can suggest on PLB or developing pcore for PLB?
Thanks.
Last edited by zrcao (2007-May-15 12:07:22)
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1) The new design uses the standalone BSP (i.e. no OS)
2) There are a few documents included with the EDK that are pretty helpful:
<EDK_ROOT>\doc\usenglish\plb_usage.pdf
<EDK_ROOT>\hw\XilinxProcessorIPLib\pcores\plb_ipif_v1_00_f\doc\plb_ipif.pdf
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Can't wait to see your new reference design!
The OFDM core's packet buffers are now attached to the PLB, Xilkernel is no longer used and the Ethernet MAC is used in interrupt/simple DMA mode.
So the DMA happens between the Ethernet MAC FIFO and OFDM core's packet buffers in both direction?
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OFDM -> Ethernet transfers are driven by the EMAC's DMA. Ethernet -> OFDM still requires an intermediate buffer to handle the case of the wireless MAC needing to transmit an ACK while in timeout (i.e. sending an ACK before attempting to re-transmit a previous data packet). We're working on a way around this too, though it may not make it into the next reference design.
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Are you planning to use the new radio_controller APIs? It seems to me that the radio setup part is still using the old APIs.
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The new OFDM reference design uses the latest radio controller and bridge pcores and drivers.
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