feat(AM62PX): Add PREEMPT_RT perf numbers

Add the AM62Px latency numbers for the SDK 12.0 release

Signed-off-by: Bryan Brattlof <bb@ti.com>

Author: bryanbrattlof

source/devices/AM62PX/linux/RT_Linux_Performance_Guide.rst

@@ -36,4 +36,49 @@ https://e2e.ti.com/ or https://support.ti.com/
 System Benchmarks
 *****************
 
-|
+Stress-ng and Cyclic Test
+
+.. _RT-linux-performance:
+
+stress-ng (next-generation) will stress test a embedded platform in various selectable ways.
+It was designed to exercise various physical subsystems as well as the various
+operating system kernel interfaces. stress-ng can also measure test throughput rates;
+this can be useful to observe performance changes across different operating system or types of hardware.
+
+Cyclictest is most commonly used for benchmarking RT systems.
+It is one of the most frequently used tools for evaluating the relative performance of real-time systems.
+Some performance tests which use Cyclictest are System benchmarking, Latency debugging with tracing and
+approximating application performance.
+
+Test commands used for running stress-ng and cyclictest together
+
+.. code:: console
+
+   stress-ng --cpu-method=all -c 4 &
+   cyclictest -m -Sp80 -D6h -h400 -i200 -M -q
+
+The following summarizes the latencies observed using the yocto based
+default SDK image
+
+.. note::
+
+   Using the OP-TEE TRNG driver can impact this benchmark's performance due to
+   frequent context switching between Normal World (Linux) and Secure World (OP-TEE),
+   that occurs when the kernel's hardware random number generator interface
+   (hwrng) requests entropy from the secure TRNG to replenish the Linux entropy
+   pool.
+
+   The Linux TRNG driver can mitigate these latency spikes. This involves
+   enabling the Pseudo RNG driver in OP-TEE as documented in the Foundational
+   Components section: :ref:`building-optee-with-prng`, and enabling the RNG
+   node in the Linux kernel device tree. This way the HW TRNG is accessed from
+   the kernel itself.
+
+.. csv-table::
+   :header: "Latencies","CPU 0","CPU 1","CPU 2","CPU 3"
+
+   "Minimum (usec)","4","4","4","4"
+   "Average (usec)","5","5","5","5"
+   "Maximum (usec)","39","42","44","47"
+
+.. image:: img/rt-cpu-method-all-latency-histogram.png