.. index::
   POM AXI lite

.. _pom_axi_lite:


POM AXI-Lite interface memory map
:::::::::::::::::::::::::::::::::

The POM hardware runtime includes an optional AXI-Lite interface to
access internal debug registers (read-only). The mapped address space is
16KB (14-bit addresses).

The available registers and their respective addresses are (size in
bytes):

+-----------------------+-----------+--------------+-----------------+
| Register name         | Address   | Size         | Description     |
+=======================+===========+==============+=================+
| COPY_OPT_IN           | 0x0       | 4            | Number of copy  |
|                       |           |              | in              |
|                       |           |              | optimizations   |
|                       |           |              | in the command  |
|                       |           |              | in queue (both  |
|                       |           |              | internal and    |
|                       |           |              | external)       |
+-----------------------+-----------+--------------+-----------------+
| COPY_OPT_OUT          | 0x4       | 4            | Number of copy  |
|                       |           |              | in              |
|                       |           |              | optimizations   |
|                       |           |              | in the command  |
|                       |           |              | in queue (both  |
|                       |           |              | internal and    |
|                       |           |              | external)       |
+-----------------------+-----------+--------------+-----------------+
| ACC_AVAIL             | 0x8       | 8            | One bit per     |
|                       |           |              | accelerator,    |
|                       |           |              | indicating the  |
|                       |           |              | availability    |
|                       |           |              | status          |
+-----------------------+-----------+--------------+-----------------+
| QUEUE_NEMPTY          | 0x10      | 8            | One bit per     |
|                       |           |              | accelerator,    |
|                       |           |              | indicating if   |
|                       |           |              | the internal    |
|                       |           |              | queue is not    |
|                       |           |              | empty           |
+-----------------------+-----------+--------------+-----------------+
| CMD_IN_N_CMDS         | 0x800     | 4 per acc    | For each        |
|                       |           |              | accelerator,    |
|                       |           |              | the number of   |
|                       |           |              | commands it has |
|                       |           |              | received        |
+-----------------------+-----------+--------------+-----------------+
| CMD_OUT_N_CMDS        | 0x900     | 4 per acc    | For each        |
|                       |           |              | accelerator,    |
|                       |           |              | the number of   |
|                       |           |              | commands it has |
|                       |           |              | issued          |
+-----------------------+-----------+--------------+-----------------+
| ACC_AVAIL_COUNT       | 0xA00     | 8 per acc    | For each        |
|                       |           |              | accelerator,    |
|                       |           |              | the total       |
|                       |           |              | number of       |
|                       |           |              | execution       |
|                       |           |              | cycles          |
+-----------------------+-----------+--------------+-----------------+

How to enable the AXI-Lite interface
------------------------------------

You can enable it with the ``--enable_pom_axilite`` flag in AIT.
For a full list of AIT options, see :ref:`ait_help`

How to read the registers with QDMA
-----------------------------------

You can use the script located in the
https://pm.bsc.es/gitlab/ompss-at-fpga/rtl/meep-ompss-fpga-cluster repository,
under ``scripts/axilite_cntrl.py``.

.. code-block:: text

   python3 $MEEP-OMPSS-FPGA-CLUSTER/scripts/axilite_cntrl.py --read_pom

The script needs the ``XTASKS_PCI_DEV`` variable.

If you are using OMPIF, you can read all registers, including the
message sender and receiver, with the ``cluster.json`` file.

.. code-block:: text

   python3 $MEEP-OMPSS-FPGA-CLUSTER/scripts/axilite_cntrl.py --cluster cluster.json

If some FPGAs are on remote nodes, the script automatically launches
servers on each remote node. However, you need to have the
``xtasks_devs_$(hostname).sh`` files in the current working directory.