Add documentation to logging service
Documentation detailing the specifics of the logging service.
Signed-off-by: Gabor Toth <gabor.toth2@arm.com>
Signed-off-by: Gabor Ambrus <gabor.ambrus@arm.com>
Change-Id: I994d2879a0cab710b8f1fc25dfc283e94ca5e582
diff --git a/docs/services/logging-service-description.rst b/docs/services/logging-service-description.rst
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+Logging Service
+=================
+The Logging service is intended to be a mechanism that provides a means to print in the context
+of a secure partition. All other secure partitions in a given environment will utilize a
+handler to push any data to this SP. The current default behavior is where the logging service
+will send the data to a UART peripheral viewable by a terminal device (see: :ref:`UART backend`).
+
+In case the logging with the logging SP fails (e.g. in case the logging SP is not deployed, still
+booting, etc.) log messages fall back to the default logging mechanism.
+
+UART backend
+------------
+The UART backend for the logging SP outputs the log messages to an UART device. It relies on an
+UART platform adapter that provides a generic interface to interact with an UART device.
+The exact driver implementation is to be provided by the platform.
+The platform specific driver configuration (base-address) is hosted in the SP manifest.
+Platform code is responsible for reading the config data from the config store upon boot.
+Currently a PL011 driver is provided for the *AEM FVP* platform.
+
+Testing the Logging Service
+-------------------------------
+Component-Level Test Suites
+'''''''''''''''''''''''''''
+The logging components will be targeted by component-test and unit-test cases.
+
+Service-Level Test Suites
+'''''''''''''''''''''''''
+*ts-service-test* may implement logging service calls, although verifying the log messages would
+be difficult, so the scope is limited. (Unit and component test cases can account for this.)
+
+Environment Tests
+'''''''''''''''''
+The logging SP's UART backend relies on the UART peripheral. Test have been added to the
+*env_test* SP deployment to check the basic functionality of the UART device, but the
+verification of the results is not possible, as the peripheral does not provide a way
+(e.g. error bit) to check whether the printing (*putc*) was successful.
+Tests included in the *env_test* SP deployment may be invoked from Linux user-space using the
+*ts-remote-test/arm-linux* deployment.
+
+
+*Copyright (c) 2023, Arm Limited and Contributors. All rights reserved.*
+
+SPDX-License-Identifier: BSD-3-Clause