[edk2-platforms][PATCH 1/5] Platform/RPi: Fix overlap of SoC registers and RAM

["Pete Batard" <pete@akeo.ie>]

From: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Having RAM and SoC register regions overlap is problematic for MMIO,
since, at the very least, we don't want these regions to be declared
as cacheable.

Signed-off-by: Pete Batard <pete@akeo.ie>
---
 Platform/RaspberryPi/Library/PlatformLib/RaspberryPiMem.c | 36 +++++++++++++-------
 1 file changed, 23 insertions(+), 13 deletions(-)

diff --git a/Platform/RaspberryPi/Library/PlatformLib/RaspberryPiMem.c b/Platform/RaspberryPi/Library/PlatformLib/RaspberryPiMem.c
index cc761bea1307..781cf78b83d3 100644
--- a/Platform/RaspberryPi/Library/PlatformLib/RaspberryPiMem.c
+++ b/Platform/RaspberryPi/Library/PlatformLib/RaspberryPiMem.c
@@ -60,7 +60,7 @@ ArmPlatformGetVirtualMemoryMap (
 {
   UINTN                         Index = 0;
   UINTN                         GpuIndex;
-  INT64                         ExtendedMemorySize;
+  INT64                         SystemMemorySize;
   ARM_MEMORY_REGION_DESCRIPTOR  *VirtualMemoryTable;
 
   // Early output of the info we got from VideoCore can prove valuable.
@@ -120,21 +120,21 @@ ArmPlatformGetVirtualMemoryMap (
   VirtualMemoryInfo[Index].Type             = RPI_MEM_RESERVED_REGION;
   VirtualMemoryInfo[Index++].Name           = L"GPU Reserved";
 
-  // Compute the amount of extended RAM available on this platform
-  ExtendedMemorySize = SIZE_256MB;
-  ExtendedMemorySize <<= (mBoardRevision >> 20) & 0x07;
-  ExtendedMemorySize -= SIZE_1GB;
-  if (ExtendedMemorySize > 0) {
-    VirtualMemoryTable[Index].PhysicalBase  = FixedPcdGet64 (PcdExtendedMemoryBase);
-    VirtualMemoryTable[Index].VirtualBase   = VirtualMemoryTable[Index].PhysicalBase;
-    VirtualMemoryTable[Index].Length        = ExtendedMemorySize;
-    VirtualMemoryTable[Index].Attributes    = ARM_MEMORY_REGION_ATTRIBUTE_WRITE_BACK;
-    VirtualMemoryInfo[Index].Type           = RPI_MEM_BASIC_REGION;
-    VirtualMemoryInfo[Index++].Name         = L"Extended System RAM";
-  }
+  // Compute the total RAM size available on this platform
+  SystemMemorySize = SIZE_256MB;
+  SystemMemorySize <<= (mBoardRevision >> 20) & 0x07;
+
+  //
+  // Ensure that what we declare as System Memory doesn't overlap with the
+  // Bcm2836 SoC registers. This can be achieved through a MIN () with the
+  // base address since SystemMemoryBase is 0 (we assert if it isn't).
+  //
+  SystemMemorySize = MIN(SystemMemorySize, BCM2836_SOC_REGISTERS);
 
   // Extended SoC registers (PCIe, genet, ...)
   if (BCM2711_SOC_REGISTERS > 0) {
+    // Same overlap protection as above for the Bcm2711 SoC registers
+    SystemMemorySize                        = MIN(SystemMemorySize, BCM2711_SOC_REGISTERS);
     VirtualMemoryTable[Index].PhysicalBase  = BCM2711_SOC_REGISTERS;
     VirtualMemoryTable[Index].VirtualBase   = VirtualMemoryTable[Index].PhysicalBase;
     VirtualMemoryTable[Index].Length        = BCM2711_SOC_REGISTER_LENGTH;
@@ -155,6 +155,16 @@ ArmPlatformGetVirtualMemoryMap (
   VirtualMemoryInfo[Index].Type             = RPI_MEM_RESERVED_REGION;
   VirtualMemoryInfo[Index++].Name           = L"SoC Reserved (283x)";
 
+  // If we have RAM above the 1 GB mark, declare it
+  if (SystemMemorySize - SIZE_1GB > 0) {
+    VirtualMemoryTable[Index].PhysicalBase  = FixedPcdGet64 (PcdExtendedMemoryBase);
+    VirtualMemoryTable[Index].VirtualBase   = VirtualMemoryTable[Index].PhysicalBase;
+    VirtualMemoryTable[Index].Length        = SystemMemorySize - SIZE_1GB;
+    VirtualMemoryTable[Index].Attributes    = ARM_MEMORY_REGION_ATTRIBUTE_WRITE_BACK;
+    VirtualMemoryInfo[Index].Type           = RPI_MEM_BASIC_REGION;
+    VirtualMemoryInfo[Index++].Name         = L"Extended System RAM";
+  }
+
   // End of Table
   VirtualMemoryTable[Index].PhysicalBase    = 0;
   VirtualMemoryTable[Index].VirtualBase     = 0;
-- 
2.21.0.windows.1