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Observer qswsjs
Observer
6,193 Views
Registered: ‎07-18-2013

AXI DMA cyclic mode

  Hi all

       

I'm using the AXI Direct Memory Access (AXI DMA) IP(v7.1) in cyclic mode (and thus scatter-gather mode, too).

We are running Vivado 2014.2 targeting a Zynq on a ZC702.PG021of AXI DMA(V7.1) says that it support cyclic mode!

Does the AXI DMA version 7.1 supplied with v2014.2 of vivado support Cyclic DMA mode ? I have config the AXI DMA V7.1 in scatter gather cyclic mode , but when I have transfered the last descriptor buffer,the tready of DMA pull down ,it doesnt transfer to the first descriptor again ! Do you know the problem ? please give me some advice ,thanks! 

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8 Replies
Xilinx Employee
Xilinx Employee
6,183 Views
Registered: ‎08-02-2011

Re: AXI DMA cyclic mode

Hey,

Do you have the tail descriptor's 'next descriptor' field pointing back to the first descriptor in the chain?
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Observer qswsjs
Observer
6,170 Views
Registered: ‎07-18-2013

Re: AXI DMA cyclic mode

Hi bwiec,


Thanks for your reply! I use AXI DMA linux driver xilinx_axidma.c,I applied for the descriptor,the driver use the API list_add_tail(&new->node, &first->tx_list) set tail descriptor's 'next descriptor' pointing back to the first descriptor.So I think I have set tail descriptor's 'next descriptor' pointing back to the first descriptor,to use an cyclic buffer descriptor. is it right?

 

Does the AXI DMA(V7.1) suppport cyclic mode? In another post(http://forums.xilinx.com/t5/Embedded-Processor-System-Design/AXI-DMA-Cyclic-DMA-Mode/m-p/386379/highlight/false#M10244),someone say that in the AXI DMA (V8.0) to support the cyclic mode ? Can you help me confirm it? Thanks a lot !

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Xilinx Employee
Xilinx Employee
6,150 Views
Registered: ‎08-02-2011

Re: AXI DMA cyclic mode

Yes, the AXI DMA v7.1 does support cycic mode (though not when multi-channel mode is used).

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Observer qswsjs
Observer
6,144 Views
Registered: ‎07-18-2013

Re: AXI DMA cyclic mode

hi bwies,thanks!

 Sorry,I have another question ! Does the AXI DMA linux driver(xilinx_axidma.c) have been updated to supported cyclic mode?

As far as I know, Linux driver hasn't been updated to support. Do we need modify the linux driver to support cyclic mode?thanks!

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Community Manager
Community Manager
6,134 Views
Registered: ‎06-14-2012

Re: AXI DMA cyclic mode

Yes you are right. Linux driver doesnt support cyclic mode.Its only in standalone driver.

 

I will raise a CR for this.

 

Regards

Sikta

Observer qswsjs
Observer
6,089 Views
Registered: ‎07-18-2013

Re: AXI DMA cyclic mode

Thanks skitap for your reply!

I encountered this problem now, trapped here, no progress, when can you help me update the Linux driver to support cyclic mode? I'm very grateful to you help me to solve this problem!

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Adventurer
Adventurer
5,640 Views
Registered: ‎10-17-2014

Re: AXI DMA cyclic mode

Hi bwiec,

Could you show me some example about what you said multi-channel mode ? I'm working on the KC705 and
in Vivado, and I can't init the DMA in that mode.

Thank you!

Regards,
Makon
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Voyager
Voyager
3,260 Views
Registered: ‎04-04-2014

Re: AXI DMA cyclic mode

So, what was the conclusion here, other than the linux driver is to be updated to support cyclic DMA?

 

It's just that I see this very same issue in simulation.

 

Is cycle BD mode broken? 

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