On 12/11/19 12:25 PM, Pete Batard wrote:
From: Ard Biesheuvel <ard.biesheu...@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 <p...@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;

TIL I learn this field is 3 bits (I thought it was 4).

+
+  //
+  // 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).

Is the later comment "// On the Pi 3 the SoC registers may overlap VideoCore => fix this
" still accurate?

+  //
+  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)";

Sigh, the 2711/2838 naming is very confusing.

+ // 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;


Reviewed-by: Philippe Mathieu-Daude <phi...@redhat.com>


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