ArmPlatformPkg/HdLcdArmVExpressLib: use write-combine mapping for VRAM

Replace the uncached memory mapping of the framebuffer with a write-
combining one. This improves performance, and avoids issues with
unaligned accesses and DC ZVA instructions performed by the accelerated
memcpy/memset routines.

Instead of manipulating the memory attributes directly, use the
SetMemorySpaceAttributes() DXE services, which validates the attributes
against the capabilities of the region before making the actual change.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Jeremy Linton <jeremy.linton@arm.com>
Tested-by: Ryan Harkin <ryan.harkin@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

2 files changed, 6 insertions, 9 deletions

diff --git a/ArmPlatformPkg/ArmVExpressPkg/Library/HdLcdArmVExpressLib/HdLcdArmVExpress.c b/ArmPlatformPkg/ArmVExpressPkg/Library/HdLcdArmVExpressLib/HdLcdArmVExpress.c
index 67b2f14bee..b1106ee19b 100644
--- a/ArmPlatformPkg/ArmVExpressPkg/Library/HdLcdArmVExpressLib/HdLcdArmVExpress.c
+++ b/ArmPlatformPkg/ArmVExpressPkg/Library/HdLcdArmVExpressLib/HdLcdArmVExpress.c
@@ -18,11 +18,11 @@
 #include <Library/IoLib.h>

 #include <Library/PcdLib.h>

 #include <Library/DebugLib.h>

+#include <Library/DxeServicesTableLib.h>

 #include <Library/LcdPlatformLib.h>

 #include <Library/MemoryAllocationLib.h>

 #include <Library/UefiBootServicesTableLib.h>

 

-#include <Protocol/Cpu.h>

 #include <Protocol/EdidDiscovered.h>

 #include <Protocol/EdidActive.h>

 

@@ -119,7 +119,6 @@ LcdPlatformGetVram (
   )

 {

   EFI_STATUS              Status;

-  EFI_CPU_ARCH_PROTOCOL  *Cpu;

   EFI_ALLOCATE_TYPE       AllocationType;

 

   // Set the vram size

@@ -138,12 +137,9 @@ LcdPlatformGetVram (
     return Status;

   }

 

-  // Ensure the Cpu architectural protocol is already installed

-  Status = gBS->LocateProtocol (&gEfiCpuArchProtocolGuid, NULL, (VOID **)&Cpu);

-  ASSERT_EFI_ERROR(Status);

-

-  // Mark the VRAM as un-cacheable. The VRAM is inside the DRAM, which is cacheable.

-  Status = Cpu->SetMemoryAttributes (Cpu, *VramBaseAddress, *VramSize, EFI_MEMORY_UC);

+  // Mark the VRAM as write-combining. The VRAM is inside the DRAM, which is cacheable.

+  Status = gDS->SetMemorySpaceAttributes (*VramBaseAddress, *VramSize,

+                  EFI_MEMORY_WC);

   ASSERT_EFI_ERROR(Status);

   if (EFI_ERROR(Status)) {

     gBS->FreePages (*VramBaseAddress, EFI_SIZE_TO_PAGES (*VramSize));

diff --git a/ArmPlatformPkg/ArmVExpressPkg/Library/HdLcdArmVExpressLib/HdLcdArmVExpressLib.inf b/ArmPlatformPkg/ArmVExpressPkg/Library/HdLcdArmVExpressLib/HdLcdArmVExpressLib.inf
index 7807247379..dff17e86fd 100644
--- a/ArmPlatformPkg/ArmVExpressPkg/Library/HdLcdArmVExpressLib/HdLcdArmVExpressLib.inf
+++ b/ArmPlatformPkg/ArmVExpressPkg/Library/HdLcdArmVExpressLib/HdLcdArmVExpressLib.inf
@@ -32,8 +32,9 @@ HdLcdArmVExpress.c
   ArmPlatformPkg/ArmVExpressPkg/ArmVExpressPkg.dec

 

 [LibraryClasses]

-  BaseLib

   ArmPlatformSysConfigLib

+  BaseLib

+  DxeServicesTableLib

 

 [Protocols]

   gEfiEdidDiscoveredProtocolGuid                # Produced