[PATCH v4 02/14] ArmPkg/ArmSvcLib: Return x4-x7 in output parameters

["Sughosh Ganu" <sughosh.ganu@linaro.org>]

From: Achin Gupta <achin.gupta@arm.com>

The Arm SMC calling convention standard v1.2 allows 8 input and output
parameter registers. The FF-A specification relies on this
communication. This patch extends the number of output registers
returned by ArmCallSvc() to match this convention.

Signed-off-by: Achin Gupta <achin.gupta@arm.com>
Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
---

Changes since V3: None

 ArmPkg/Include/Library/ArmSvcLib.h        | 10 ++++++++--
 ArmPkg/Library/ArmSvcLib/AArch64/ArmSvc.S |  4 +++-
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/ArmPkg/Include/Library/ArmSvcLib.h b/ArmPkg/Include/Library/ArmSvcLib.h
index a94ead1965..a4414270f3 100644
--- a/ArmPkg/Include/Library/ArmSvcLib.h
+++ b/ArmPkg/Include/Library/ArmSvcLib.h
@@ -27,10 +27,16 @@ typedef struct {
 /**
   Trigger an SVC call
 
-  SVC calls can take up to 7 arguments and return up to 4 return values.
-  Therefore, the 4 first fields in the ARM_SVC_ARGS structure are used
+  SVC calls can take up to 8 arguments and return up to 8 return values.
+  Therefore, the 8 first fields in the ARM_SVC_ARGS structure are used
   for both input and output values.
 
+  @param[in, out]    Args Arguments to be passed as part of the SVC call
+                     The return values of the SVC call are also placed
+                     in the same structure
+
+  @retval None
+
 **/
 VOID
 ArmCallSvc (
diff --git a/ArmPkg/Library/ArmSvcLib/AArch64/ArmSvc.S b/ArmPkg/Library/ArmSvcLib/AArch64/ArmSvc.S
index ee265f94b9..1a7c10cb79 100644
--- a/ArmPkg/Library/ArmSvcLib/AArch64/ArmSvc.S
+++ b/ArmPkg/Library/ArmSvcLib/AArch64/ArmSvc.S
@@ -33,9 +33,11 @@ ASM_PFX(ArmCallSvc):
   ldr   x9, [sp, #16]
 
   // Store the SVC returned values into the ARM_SVC_ARGS structure.
-  // A SVC call can return up to 4 values - we do not need to store back x4-x7.
+  // A SVC call can return up to 8 values
   stp   x0, x1, [x9, #0]
   stp   x2, x3, [x9, #16]
+  stp   x4, x5, [x9, #32]
+  stp   x6, x7, [x9, #48]
 
   mov   x0, x9
 
-- 
2.17.1