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Explorer
Explorer
558 Views
Registered: ‎10-12-2018

Does SOF needed for DMA RX side?

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Hi,

There are may reference where I find that SOF/EOF not needed by the RX(S2MM) transfer of the DMA. Eg. this post or the example code contains the following:

 

/* Receive BDs do not need to set anything for the control
 * The hardware will set the SOF/EOF bits per stream status
 */
XAxiDma_BdSetCtrl(BdCurPtr, 0);
XAxiDma_BdSetId(BdCurPtr, RxBufferPtr);

 

 

BUT

There are also several place which tells that SOF/EOF needed by the RX(S2MM) transfer of the DMA.

 

From the DMA userguide: (Note there is a typo in the Description...)

image.png

Or in the BSP code:

 

/* In case of Tx channel, the first BD should have been marked
 * as start-of-frame
 */
if (!(RingPtr->IsRxChannel) && !(BdCr & XAXIDMA_BD_CTRL_TXSOF_MASK)) {
	xdbg_printf(XDBG_DEBUG_ERROR, "Tx first BD does not have "
						"SOF\r\n");
	return XST_FAILURE;
}

 

 

So.

Do I need to set the RXSOF?

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Mentor watari
Mentor
529 Views
Registered: ‎06-16-2013

Re: Does SOF needed for DMA RX side?

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Hi @betontalpfa

 

It depends on what you want to do and target (ex. video signal) has like frame or not.

 

I mention about it as video signal.

 

Video signal has some control signals (Vertical synchronous (VS), horizontal synchronous (HS) and active data enable (DE) signals) and video data.

In this case, sof is "Start of frame" and eof is "end of frame".

Their signals are generated by VS.

 

Also, sof and eof are pointed out start and end of frame and VDMA detects and set new frame by them.

 

So, if your design require like frame, you should prepare sof and eof signals.

 

Best regards,

View solution in original post

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2 Replies
Mentor watari
Mentor
530 Views
Registered: ‎06-16-2013

Re: Does SOF needed for DMA RX side?

Jump to solution

Hi @betontalpfa

 

It depends on what you want to do and target (ex. video signal) has like frame or not.

 

I mention about it as video signal.

 

Video signal has some control signals (Vertical synchronous (VS), horizontal synchronous (HS) and active data enable (DE) signals) and video data.

In this case, sof is "Start of frame" and eof is "end of frame".

Their signals are generated by VS.

 

Also, sof and eof are pointed out start and end of frame and VDMA detects and set new frame by them.

 

So, if your design require like frame, you should prepare sof and eof signals.

 

Best regards,

View solution in original post

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Explorer
Explorer
481 Views
Registered: ‎10-12-2018

Re: Does SOF needed for DMA RX side?

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Finally, root-cause of my problem was not about the SOF/EOF. Just the debugger distracted me, because it stepped into a branch (due to -O2 optimization) which condition based on the SOF availability.

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