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Altera_Forum
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10 years ago

PCIe with DMA interface locks RD_DMA_LAST_PTR reaches 127 (7F)

Hi, I have PCIe Hard IP with internal DMA interface (14.0 compiled). I wrote a PC window 7 device driver. When RD_DMA_LAST_PTR reaches 0x7Fsoftare writes 0x7F and the last descriptor ID to the PTR...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
10 years ago

If your DMA controller is doing Avalon burst transfers into the Txs port of the PCIe block then the maximum burst size is limited to (I believe) that which will normally generate a single TLP - ie burst 16 giving TLPs of 128 bytes with a 64bit interface.

The 'simple' dma controller can't be configured to do that for lomng transfers.

The 'scatter-gather' DMA controller can, but it is a bit like using an atomic bomb to shell a peanut.

OTOH if you are talking about the new DMA interface within the PCIe block itself I can't help.