EmbeddedPkg/CoherentDmaLib: add support for non-1:1 DMA translation

Bring CoherentDmaLib in line with ArmDmaLib, and add support for
defining a static offset between the host's and the bus master's
view of memory.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

EmbeddedPkg/EmbeddedPkg.dec

@@ -205,3 +205,10 @@
 
 [PcdsFixedAtBuild.common, PcdsDynamic.common]
   gEmbeddedTokenSpaceGuid.PcdFdtDevicePaths|L""|VOID*|0x00000055
+
+  #
+  # Value to add to a host address to obtain a device address, using
+  # unsigned 64-bit integer arithmetic. This means we can rely on
+  # truncation on overflow to specify negative offsets.
+  #
+  gEmbeddedTokenSpaceGuid.PcdDmaDeviceOffset|0x0|UINT64|0x0000058

EmbeddedPkg/Library/CoherentDmaLib/CoherentDmaLib.c

@@ -19,6 +19,14 @@
 #include <Library/MemoryAllocationLib.h>
 
 
+STATIC
+PHYSICAL_ADDRESS
+HostToDeviceAddress (
+  IN  VOID      *Address
+  )
+{
+  return (PHYSICAL_ADDRESS)(UINTN)Address + PcdGet64 (PcdDmaDeviceOffset);
+}
 
 /**
   Provides the DMA controller-specific addresses needed to access system memory.
@@ -50,7 +58,7 @@ DmaMap (
   OUT    VOID                           **Mapping
   )
 {
-  *DeviceAddress = (PHYSICAL_ADDRESS)(UINTN)HostAddress;
+  *DeviceAddress = HostToDeviceAddress (HostAddress);
   *Mapping = NULL;
   return EFI_SUCCESS;
 }

EmbeddedPkg/Library/CoherentDmaLib/CoherentDmaLib.inf

@@ -31,3 +31,6 @@
 [LibraryClasses]
   DebugLib
   MemoryAllocationLib
+
+[Pcd]
+  gEmbeddedTokenSpaceGuid.PcdDmaDeviceOffset