board to board
Posted:
Hi Eli,
Firstly, thank you for taking the time to write the "Down to the TLP" blogs. They've been extremely helpful in understanding how it all works.
I have two PCIe cards, each with Altera FPGAs on them with their PCIe HIP / DMA reference design in them. I can DMA to and from each device perfectly. Both devices (let's call them device1 and device2) have the DMA controller(s) in BAR 0 and 4K of SRAM in BAR 2. From the host, I can DMA to and from the SRAM (to/from host memory). I verify the data by inspecting BAR 2. I then tried to DMA from device1's SRAM to the physical address of device2's bar2 mapping. From what I've read, this should be legal.. ? It actually works as long as the dma length is one single 32-bit word. If i increase it, even to 2, it hangs the system. Can you think of any reasons why this might not work? The DMA turns into a write (from device1) to host physical memory (so the ID would be for the host, not for device 2), I assume? Is that the problem? Any insight greatly appreciated! Thank you!
Firstly, thank you for taking the time to write the "Down to the TLP" blogs. They've been extremely helpful in understanding how it all works.
I have two PCIe cards, each with Altera FPGAs on them with their PCIe HIP / DMA reference design in them. I can DMA to and from each device perfectly. Both devices (let's call them device1 and device2) have the DMA controller(s) in BAR 0 and 4K of SRAM in BAR 2. From the host, I can DMA to and from the SRAM (to/from host memory). I verify the data by inspecting BAR 2. I then tried to DMA from device1's SRAM to the physical address of device2's bar2 mapping. From what I've read, this should be legal.. ? It actually works as long as the dma length is one single 32-bit word. If i increase it, even to 2, it hangs the system. Can you think of any reasons why this might not work? The DMA turns into a write (from device1) to host physical memory (so the ID would be for the host, not for device 2), I assume? Is that the problem? Any insight greatly appreciated! Thank you!