Changes to support updated register usage in SMCCC v1.2

From AArch64 state, arguments are passed in registers W0-W7(X0-X7)
and results are returned in W0-W7(X0-X7) for SMC32(SMC64) calls.
From AArch32 state, arguments are passed in registers R0-R7 and
results are returned in registers R0-R7 for SMC32 calls.

Most of the functions and macros already existed to support using
upto 8 registers for passing/returning parameters/results. Added
few helper macros for SMC calls from AArch32 state.

Link to the specification:
https://developer.arm.com/docs/den0028/c

Change-Id: I87976b42454dc3fc45c8343e9640aa78210e9741
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>

2 files changed, 24 insertions, 6 deletions

diff --git a/docs/design/firmware-design.rst b/docs/design/firmware-design.rst
index 4958fc097..4e380bfe1 100644
--- a/docs/design/firmware-design.rst
+++ b/docs/design/firmware-design.rst
@@ -978,8 +978,8 @@ manipulation; and with ``flags`` indicating the security state of the caller. Th
 framework finally sets up the execution stack for the handler, and invokes the
 services ``handle()`` function.
 
-On return from the handler the result registers are populated in X0-X3 before
-restoring the stack and CPU state and returning from the original SMC.
+On return from the handler the result registers are populated in X0-X7 as needed
+before restoring the stack and CPU state and returning from the original SMC.
 
 Exception Handling Framework
 ----------------------------
diff --git a/docs/getting_started/rt-svc-writers-guide.rst b/docs/getting_started/rt-svc-writers-guide.rst
index 6a06025ef..5375b659d 100644
--- a/docs/getting_started/rt-svc-writers-guide.rst
+++ b/docs/getting_started/rt-svc-writers-guide.rst
@@ -244,17 +244,35 @@ The handler is responsible for:
 
    TF-A expects owning entities to follow this recommendation.
 
-#. Returning the result to the caller. The `SMCCC`_ allows for up to 256 bits
-   of return value in SMC64 using X0-X3 and 128 bits in SMC32 using W0-W3. The
-   framework provides a family of macros to set the multi-register return
-   value and complete the handler:
+#. Returning the result to the caller. Based on `SMCCC`_ spec, results are
+   returned in W0-W7(X0-X7) registers for SMC32(SMC64) calls from AArch64
+   state. Results are returned in R0-R7 registers for SMC32 calls from AArch32
+   state. The framework provides a family of macros to set the multi-register
+   return value and complete the handler:
 
    .. code:: c
 
+       AArch64 state:
+
        SMC_RET1(handle, x0);
        SMC_RET2(handle, x0, x1);
        SMC_RET3(handle, x0, x1, x2);
        SMC_RET4(handle, x0, x1, x2, x3);
+       SMC_RET5(handle, x0, x1, x2, x3, x4);
+       SMC_RET6(handle, x0, x1, x2, x3, x4, x5);
+       SMC_RET7(handle, x0, x1, x2, x3, x4, x5, x6);
+       SMC_RET8(handle, x0, x1, x2, x3, x4, x5, x6, x7);
+
+       AArch32 state:
+
+       SMC_RET1(handle, r0);
+       SMC_RET2(handle, r0, r1);
+       SMC_RET3(handle, r0, r1, r2);
+       SMC_RET4(handle, r0, r1, r2, r3);
+       SMC_RET5(handle, r0, r1, r2, r3, r4);
+       SMC_RET6(handle, r0, r1, r2, r3, r4, r5);
+       SMC_RET7(handle, r0, r1, r2, r3, r4, r5, r6);
+       SMC_RET8(handle, r0, r1, r2, r3, r4, r5, r6, r7);
 
 The ``cookie`` parameter to the handler is reserved for future use and can be
 ignored. The ``handle`` is returned by the SMC handler - completion of the