rtla: Documentation: Mention --deepest-idle-state

Add --deepest-idle-state to manpage and mention libcpupower dependency
in README.txt.

Link: https://lore.kernel.org/20241017140914.3200454-7-tglozar@redhat.com
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Documentation/tools/rtla/common_timerlat_options.rst

@@ -31,6 +31,14 @@
         *cyclictest* sets this value to *0* by default, use **--dma-latency** *0* to have
         similar results.
 
+**--deepest-idle-state** *n*
+        Disable idle states higher than *n* for cpus that are running timerlat threads to
+        reduce exit from idle latencies. If *n* is -1, all idle states are disabled.
+        On exit from timerlat, the idle state setting is restored to its original state
+        before running timerlat.
+
+        Requires rtla to be built with libcpupower.
+
 **-k**, **--kernel-threads**
 
         Use timerlat kernel-space threads, in contrast of **-u**.

tools/tracing/rtla/README.txt

@@ -11,6 +11,7 @@ RTLA depends on the following libraries and tools:
 
  - libtracefs
  - libtraceevent
+ - libcpupower (optional, for --deepest-idle-state)
 
 It also depends on python3-docutils to compile man pages.
 
@@ -26,6 +27,9 @@ For development, we suggest the following steps for compiling rtla:
   $ make
   $ sudo make install
   $ cd ..
+  $ cd $libcpupower_src
+  $ make
+  $ sudo make install
   $ cd $rtla_src
   $ make
   $ sudo make install