As far as I can tell the PCIe interface in 24.1 appears to be broken.
I finally did get build in 24.1 and when I got it going the debug USB/UART port started sending odd errors about the miniPCIe USB3 card, SYBA SD-MPE20142 I had stuck in a M.2 slot extender, which did work in 23.2. (note I did fix the error in 24.1 file drivers/base/Kconfig line 234 missing end quote.)
If I removed the miniPCie card the USB/UART port stop sending error messages.
On my custom FPGA card in the standard PCIe port I was not able to get any read/write DMA to work in 24.1. It can do ioctl commands , but the DRAM does not connect into PCIe bus right to do the file ops read and write DMA to the card. In 23.1 I can get PCIe read/write DMA working but not ioctl to it.
I added these vmalloc=256M cma=128M coherent-pool=96M in the /boot/extlinux extlinux.conf to get 23.1 DMA to work for PCIe using dma_alloc_coherent.
Between 24.1 and 23.2 there are changes made to the drivers/base files that do the DMA memory allocation. If the error drivers/base/Kconfig is left in place it appears that it does not build the object files in drivers/base, so I think no ones really testing it.
My best bet is to try and figure out why my ioctl commands do not work in 23.2 and forget using 24.1 until someone other then me gets into fixing it. (I actually have iio commands working in 23.2 to my card so can use that instead of ioctl if I need to.)
What really need to be done is convince the management a nvidia that it is not acceptable to release a development product that is not fully test with good support docs; that PCIe in the TX1 needs to be supported and how to make it work well document by them, not forgoing to third party documentation etc.