[edk2-platforms][PATCH V1 15/20] ArmPkg/MmCommunicationDxe: Add support for obtaining FF-A partition ID

["Nishant Sharma" <nishant.sharma@arm.com>]

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

This patch invokes the FFA_ID_GET to obtain and stash the ID of the the
FF-A partition that implements the DXE MM communication driver. This ID
is used in subsequent patches for sending and receiving MM communication
protocol requests and responses that are packaged as FF-A messages.

Signed-off-by: Achin Gupta <achin.gupta@arm.com>
Signed-off-by: Nishant Sharma <nishant.sharma@arm.com>
---
 ArmPkg/Include/IndustryStandard/ArmFfaSvc.h         |  1 +
 ArmPkg/Drivers/MmCommunicationDxe/MmCommunication.c | 22 ++++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/ArmPkg/Include/IndustryStandard/ArmFfaSvc.h b/ArmPkg/Include/IndustryStandard/ArmFfaSvc.h
index 4a51f9fb56af..20eeb822ea56 100644
--- a/ArmPkg/Include/IndustryStandard/ArmFfaSvc.h
+++ b/ArmPkg/Include/IndustryStandard/ArmFfaSvc.h
@@ -17,6 +17,7 @@
 #define ARM_FFA_SVC_H_
 
 #define ARM_SVC_ID_FFA_VERSION_AARCH32               0x84000063
+#define ARM_SVC_ID_FFA_ID_GET_AARCH32                0x84000069
 #define ARM_SVC_ID_FFA_MSG_SEND_DIRECT_REQ_AARCH32   0x8400006F
 #define ARM_SVC_ID_FFA_MSG_SEND_DIRECT_RESP_AARCH32  0x84000070
 #define ARM_SVC_ID_FFA_MSG_SEND_DIRECT_REQ_AARCH64   0xC400006F
diff --git a/ArmPkg/Drivers/MmCommunicationDxe/MmCommunication.c b/ArmPkg/Drivers/MmCommunicationDxe/MmCommunication.c
index a6fcd590a65b..f907ccf7349f 100644
--- a/ArmPkg/Drivers/MmCommunicationDxe/MmCommunication.c
+++ b/ArmPkg/Drivers/MmCommunicationDxe/MmCommunication.c
@@ -23,6 +23,11 @@
 
 #include "MmCommunicate.h"
 
+//
+// Partition ID if FF-A support is enabled
+//
+STATIC UINT16  mFfaPartId;
+
 //
 // Address, Length of the pre-allocated buffer for communication with the secure
 // world.
@@ -288,6 +293,23 @@ GetMmCompatibility (
     Status = EFI_UNSUPPORTED;
   }
 
+  // If FF-A is supported then discover our ID.
+  if (FixedPcdGet32 (PcdFfaEnable) != 0) {
+
+    // Get our ID
+    ZeroMem(&SmcArgs, sizeof(SmcArgs));
+    SmcArgs.Arg0 = ARM_SVC_ID_FFA_ID_GET_AARCH32;
+    ArmCallSmc (&SmcArgs);
+    if (SmcArgs.Arg0 == ARM_SVC_ID_FFA_ERROR_AARCH32) {
+      DEBUG ((DEBUG_ERROR, "Unable to retrieve FF-A partition ID (%d).\n", SmcArgs.Arg2));
+      return EFI_UNSUPPORTED;
+    }
+    DEBUG ((DEBUG_INFO, "FF-A partition ID = 0x%lx.\n", SmcArgs.Arg2));
+    mFfaPartId = SmcArgs.Arg2;
+
+    return EFI_SUCCESS;
+  }
+
   return Status;
 }
 
-- 
2.34.1