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For PCIe DMA driver from altera multiple descriptors not working?

KChan12
Beginner
1,336 Views

Hi , We are using AVMM PCIe DMA example design and modified as per our requirement. In place of onchip memory we are using FIFO. we are using PCIe DMA driver from altera. We can tap the data lines on FIFO side and check the data using signal tap. But data is proper when one single descriptor is used. As we go for multiple descriptors (like number of Dwords:/desc 256 and no of descriptors:2 total 2 kb of data). We can see only 1kb of data on bus ie for one descriptor. Please give inputs why its is not sending properly in case of multiple decriptors or the driver doesnt support multiple descriptor.

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3 Replies
SengKok_L_Intel
Moderator
120 Views

​Hi,

The maximum transfer size for each descriptor is 1MB. If without modified the design, did you see the same behavior? What device that you are using? Are you saying, if only 1 descriptor with 2kb of data, you can also see it correctly in the FIFO?

 

Regards -SK

KChan12
Beginner
120 Views

Hi,

Thanks for reply.

For ex I am using 2 descriptor with 256 dwords ie 1 KB of data for each descriptor. I can see correct data for only one descriptor when seen through signal tap it is not working for second descriptor.

ie while using multiple descriptor , it is sending data for only one descriptor.

Thanks,

Kamlendra

SengKok_L_Intel
Moderator
120 Views

​Hi Sir,

 

Are you seeing the same problem if using Onchip memory ( original design)? How about using 1 descriptor with 2KB of data?

 

Regards -SK

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