Just to follow up with this original posting for anyone else having PCIe to endpoint DMA issues
I spoke with Martin, he used
vmalloc=256M cma=128M coherent-pool=96M to the boot parameters to get dma_alloc_coherent to give me a usable chunk.
Which work for me also.
The boot line parameters are added to /boot/extlinux.conf in the kernel
where base extlinux.conf files are located at jestpack/TX1/Linux_for_Tegra_tx1/bootloader/t210ref/ p2371-2180
the physical address returned by dma_alloc_coherent is the true PCI bus address to access memory from.
z7pcie->dmaBuf0_va = dma_alloc_coherent(&pdev->dev,DMAbuf_SIZE,&z7pcie->dmaBuf0_pba, GFP_KERNEL);
where z7pcie->dmaBuf0_pba is declared as dma_addr_t and is 64 bit address to set the endpoint DMA controller to access memory from. Note that the upper 32 address bits are zero for this physical address.
dmaBuf0_va = 0xffffffc068400000, dmaBuf0_pba = 0x00000000e8400000.