Support asynchronous method for BL3-2 initialization

This patch adds support for BL3-2 initialization by asynchronous
method where BL3-1 transfers control to BL3-2 using world switch.
After BL3-2 initialization, it transfers control to BL3-3 via SPD
service handler. The SPD service handler initializes the CPU context
to BL3-3 entrypoint depending on the return function indentifier from
TSP initialization.

Fixes ARM-software/TF-issues#184

Change-Id: I7b135c2ceeb356d3bb5b6a287932e96ac67c7a34

2 files changed, 13 insertions, 5 deletions

diff --git a/docs/firmware-design.md b/docs/firmware-design.md
index 9bdfefb..3203a52 100644
--- a/docs/firmware-design.md
+++ b/docs/firmware-design.md
@@ -811,10 +811,10 @@ and is registered using the `bl31_register_bl32_init()` function.
 Trusted Firmware supports two approaches for the SPD to pass control to BL3-2
 before returning through EL3 and running the non-trusted firmware (BL3-3):
 
-1.  In the BL3-2 initialization function, set up a secure context (see below
-    for more details of CPU context support) for this CPU and use
-    `bl31_set_next_image_type()` to request that the exit from `bl31_main()` is
-    to the BL3-2 entrypoint in Secure-EL1.
+1.  In the BL3-2 setup function, use `bl31_set_next_image_type()` to
+    request that the exit from `bl31_main()` is to the BL3-2 entrypoint in
+    Secure-EL1. BL3-1 will exit to BL3-2 using the asynchronous method by
+    calling bl31_prepare_next_image_entry() and el3_exit().
 
     When the BL3-2 has completed initialization at Secure-EL1, it returns to
     BL3-1 by issuing an SMC, using a Function ID allocated to the SPD. On
@@ -824,7 +824,8 @@ before returning through EL3 and running the non-trusted firmware (BL3-3):
     the normal world firmware BL3-3. On return from the handler the framework
     will exit to EL2 and run BL3-3.
 
-2.  In the BL3-2 initialization function, use an SPD-defined mechanism to
+2.  The BL3-2 setup function registers a initialization function using
+    `bl31_register_bl32_init()` which provides a SPD-defined mechanism to
     invoke a 'world-switch synchronous call' to Secure-EL1 to run the BL3-2
     entrypoint.
     NOTE: The Test SPD service included with the Trusted Firmware provides one
diff --git a/docs/user-guide.md b/docs/user-guide.md
index 41e7606..ef5de71 100644
--- a/docs/user-guide.md
+++ b/docs/user-guide.md
@@ -186,6 +186,13 @@ performed.
     value of `DEBUG` - i.e. by default this is only enabled for a debug
     build of the firmware.
 
+*   `TSP_INIT_ASYNC`: Choose BL3-2 initialization method as asynchronous or
+    synchronous, e.g. "(see "Initializing a BL3-2 Image" section in [Firmware
+    Design])". It can take the value 0 (BL3-2 is initialized using
+    synchronous method) or 1 (BL3-2 is initialized using asynchronous method).
+    Default is 0.
+
+
 ### Creating a Firmware Image Package
 
 FIPs are automatically created as part of the build instructions described in