Replacing details.md with details.rst

Author: virata-xilinx

host/p2p_fpga2fpga_bandwidth/details.md

@@ -0,0 +1,75 @@
+P2P FPGA to FPGA
+================
+
+PCIe peer-to-peer communication (P2P) is a PCIe feature which enables
+two PCIe devices to directly transfer data between each other without
+using host RAM as a temporary storage. The latest version of Vitis PCIe
+platforms support P2P feature via PCIe Resizable BAR Capability
+
+In this Example we highlight the data transfer between FPGA and FPGA
+devices. The current design support P2P between 2 similar FPGA devices.
+User can update the makefile if need to run P2P between different FPGA
+cards.
+
+Enable/Disable P2P
+~~~~~~~~~~~~~~~~~~
+
+XRT xbutil is used to enable/disable P2P feature and check current
+configuration. P2P configuration is persistent across warm reboot.
+Enabling or disabling P2P requires root privilege.
+
+Enabling P2P after cold boot is likely to fail because it resizes an
+existing P2P PCIe BAR to a large size and usually Linux will not reserve
+large IO memory for the PCIe bridges. A warm reboot is required in this
+scenario after which BIOS and Linux will reassign the required expanded
+IO memory resource for P2P BAR. Disabling P2P takes effect immediately.
+Currently XRT does not check if the P2P memory is in use. Administrator
+needs to make sure P2P is not in use before disabling it. The result of
+disabling P2P while it is in use is undefined.
+
+There are three possible values for P2P Enabled field :
+
++-------------------------+--------------------------------------------+
+| Value                   | Remarks                                    |
++=========================+============================================+
+| True                    | P2P is Enabled                             |
++-------------------------+--------------------------------------------+
+| False                   | P2P is Disabled                            |
++-------------------------+--------------------------------------------+
+| no iomem                | P2P is enabled in device but system could  |
+|                         | not allocate IO memory, warm reboot is     |
+|                         | needed                                     |
++-------------------------+--------------------------------------------+
+
+Enable P2P
+^^^^^^^^^^
+
+Enable P2P after power up sequence.
+
+::
+
+   # xbutil p2p --enable
+   ERROR: resoure busy, please try warm reboot
+   # xbutil query
+   ...
+   PCIe            DMA chan(bidir) MIG Calibrated  P2P Enabled
+   GEN 3x16        2               true            no iomem
+   # reboot
+   ...
+   # xbutil query
+   ...
+   PCIe            DMA chan(bidir) MIG Calibrated  P2P Enabled
+   GEN 3x16        2               true            true
+   ...
+
+Disable P2P
+^^^^^^^^^^^
+
+::
+
+   # xbutil p2p --disable
+   # xbutil query
+   ...
+   PCIe            DMA chan(bidir) MIG Calibrated  P2P Enabled
+   GEN 3x16        2               true            false
+   ...