[PATCH] MdeModulePkg/PciHostBridgeDxe: Fixed PCI DMA Map/Umap bounce buffer

[Daniil Egranov <daniil.egranov@arm.com>]

The patch corrects the logic of transferring data between a bounce
buffer and a real buffer above 4GB:
1. In the case of mapping a bounce buffer for the write operation,
data from a real buffer should be copied into a bounce
buffer.
2.In the case of unmapping a bounce buffer for the read operation,
data should be copied from a bounce buffer into a real
buffer.

The patch resolves a Juno board issue with the the grub and SATA
drives.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Daniil Egranov <daniil.egranov@arm.com>
---
 MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c b/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c
index dc06c16dc0..877fa2fd13 100644
--- a/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c
+++ b/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c
@@ -1153,12 +1153,12 @@ RootBridgeIoMap (
     }
 
     //
-    // If this is a read operation from the Bus Master's point of view,
+    // If this is a write operation from the Bus Master's point of view,
     // then copy the contents of the real buffer into the mapped buffer
     // so the Bus Master can read the contents of the real buffer.
     //
-    if (Operation == EfiPciOperationBusMasterRead ||
-        Operation == EfiPciOperationBusMasterRead64) {
+    if (Operation == EfiPciOperationBusMasterWrite ||
+        Operation == EfiPciOperationBusMasterWrite64) {
       CopyMem (
         (VOID *) (UINTN) MapInfo->MappedHostAddress,
         (VOID *) (UINTN) MapInfo->HostAddress,
@@ -1256,12 +1256,12 @@ RootBridgeIoUnmap (
   RemoveEntryList (&MapInfo->Link);
 
   //
-  // If this is a write operation from the Bus Master's point of view,
+  // If this is a read operation from the Bus Master's point of view,
   // then copy the contents of the mapped buffer into the real buffer
   // so the processor can read the contents of the real buffer.
   //
-  if (MapInfo->Operation == EfiPciOperationBusMasterWrite ||
-      MapInfo->Operation == EfiPciOperationBusMasterWrite64) {
+  if (MapInfo->Operation == EfiPciOperationBusMasterRead ||
+      MapInfo->Operation == EfiPciOperationBusMasterRead64) {
     CopyMem (
       (VOID *) (UINTN) MapInfo->HostAddress,
       (VOID *) (UINTN) MapInfo->MappedHostAddress,
-- 
2.11.0