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Honored Contributor I
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Need some advices on designing multiple DMA in a PCIE bridge chip

Hi everyone, 

 

I'm now starting to do a PCIE bridge with video and audio DMA. 

 

My final goal is to have 4 video interfaces (BT1120) and at least 4 audio interfaces (I2S) as the data input of this bridge. 

For now, only one video interface and one audio interface have been done in my design as a preliminary test. 

 

For the video part, I have the following design for DMA transfer from BT1120 to allocated memory on PC. 

Clocked video input IP --------> DMA writer from mSGDMA --------> txs port in PCIE HIP 

 

For the audio part, I write a module named "I2S module" to convert I2S to avalon st.  

The design for DMA transfer from I2S to allocated memory on PC looks like: 

I2S module --------> FIFO --------> DMA writer from mSGDMA --------> txs port in PCIE HIP 

 

Now, here comes my three questions: 

 

1. Multiple DMA arbitration problem: 

If I enable both video and audio DMA and the input video is 1080p60, how do I ensure the video DMA can generate 60 interrupts in a second? 

From what I understand, this is a multiple master to one slave design on avalon mm bus and interconnection fabric should do the arbitration automatically. Can I assign a higher priority to the video DMA part? 

 

2. Resource sharing problem: 

For my current design, each video or audio interface requires a DMA writer and a DMA dispatcher. 

Therefore, in order to achieve my final spec, my design will need at least 8 DMA writers and 8 DMA dispatchers. 

It's kind of waste because these 8 DMA writers and 8 DMA dispatchers cannot work at the same time. 

It would be better if my design becomes as follows: 

Clocked video input IP--> MUX --> DMA writer from mSGDMA --> txs port in PCIE HIP 

I2S module ---> FIFO ---> 

 

The selection signal of MUX may come from some sort of priority arbitrator circuits. 

For this kind of design, how should I do to avoid data loss? Increase the size of FIFO? Add a FIFO after clocked video input IP? 

 

3. FIFO size: 

Is there a good way to decide the required size of FIFO? 

For now, I just use try & error to find a suitable size of the FIFO. 

 

Any advice and idea are welcome to my questions. Thanks.
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