[edk2-platforms][PATCH 6/6] Platform/RPi4: Add ACPI basic mode build option

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

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

Add an ACPI_BASIC_MODE_ENABLE flag to produces builds intended to run in
ACPI mode without any additional requirements (memory limits, acpi=force,
etc).

This flag is disabled by default.

Signed-off-by: Pete Batard <pete@akeo.ie>
---
 Platform/RaspberryPi/Library/PlatformLib/PlatformLib.inf  | 3 +++
 Platform/RaspberryPi/Library/PlatformLib/RaspberryPiMem.c | 8 ++++++++
 Platform/RaspberryPi/RPi4/RPi4.dsc                        | 6 ++++++
 Platform/RaspberryPi/RPi4/RPi4.fdf                        | 3 +++
 Platform/RaspberryPi/RPi4/Readme.md                       | 9 +++++++--
 Platform/RaspberryPi/RaspberryPi.dec                      | 3 +++
 6 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/Platform/RaspberryPi/Library/PlatformLib/PlatformLib.inf b/Platform/RaspberryPi/Library/PlatformLib/PlatformLib.inf
index 77cdbe399a06..9abcc2cc0075 100644
--- a/Platform/RaspberryPi/Library/PlatformLib/PlatformLib.inf
+++ b/Platform/RaspberryPi/Library/PlatformLib/PlatformLib.inf
@@ -59,5 +59,8 @@ [FixedPcd]
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwWorkingSize
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwSpareSize
 
+[FeaturePcd]
+  gRaspberryPiTokenSpaceGuid.PcdAcpiBasicMode
+
 [Ppis]
   gArmMpCoreInfoPpiGuid
diff --git a/Platform/RaspberryPi/Library/PlatformLib/RaspberryPiMem.c b/Platform/RaspberryPi/Library/PlatformLib/RaspberryPiMem.c
index f8223d1b94e8..4b388465cdde 100644
--- a/Platform/RaspberryPi/Library/PlatformLib/RaspberryPiMem.c
+++ b/Platform/RaspberryPi/Library/PlatformLib/RaspberryPiMem.c
@@ -155,6 +155,14 @@ ArmPlatformGetVirtualMemoryMap (
   VirtualMemoryInfo[Index].Type             = RPI_MEM_UNMAPPED_REGION;
   VirtualMemoryInfo[Index++].Name           = L"SoC Reserved (283x)";
 
+  if (FeaturePcdGet (PcdAcpiBasicMode)) {
+    //
+    // Limit the memory to 3 GB to work around the DMA bugs in the SoC without
+    // having to rely on IORT or _DMA descriptions.
+    //
+    SystemMemorySize = MIN(SystemMemorySize, 3U * SIZE_1GB);
+  }
+
   // If we have RAM above the 1 GB mark, declare it
   if (SystemMemorySize - SIZE_1GB > 0) {
     VirtualMemoryTable[Index].PhysicalBase  = FixedPcdGet64 (PcdExtendedMemoryBase);
diff --git a/Platform/RaspberryPi/RPi4/RPi4.dsc b/Platform/RaspberryPi/RPi4/RPi4.dsc
index ccf5bd5b9ef3..02de104df5bf 100644
--- a/Platform/RaspberryPi/RPi4/RPi4.dsc
+++ b/Platform/RaspberryPi/RPi4/RPi4.dsc
@@ -39,6 +39,7 @@ [Defines]
   DEFINE INCLUDE_TFTP_COMMAND    = FALSE
   DEFINE DEBUG_PRINT_ERROR_LEVEL = 0x8000004F
   DEFINE PL011_ENABLE            = FALSE
+  DEFINE ACPI_BASIC_MODE_ENABLE  = FALSE
 
 ################################################################################
 #
@@ -263,6 +264,8 @@ [PcdsFeatureFlag.common]
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutGopSupport|TRUE
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutUgaSupport|FALSE
 
+  gRaspberryPiTokenSpaceGuid.PcdAcpiBasicMode|$(ACPI_BASIC_MODE_ENABLE)
+
 [PcdsFixedAtBuild.common]
   gEfiMdePkgTokenSpaceGuid.PcdMaximumUnicodeStringLength|1000000
   gEfiMdePkgTokenSpaceGuid.PcdMaximumAsciiStringLength|1000000
@@ -558,12 +561,15 @@ [Components.common]
   MdeModulePkg/Universal/Console/TerminalDxe/TerminalDxe.inf
   MdeModulePkg/Universal/SerialDxe/SerialDxe.inf
   Platform/RaspberryPi/Drivers/DisplayDxe/DisplayDxe.inf
+  EmbeddedPkg/Drivers/ConsolePrefDxe/ConsolePrefDxe.inf
 
   MdeModulePkg/Universal/HiiDatabaseDxe/HiiDatabaseDxe.inf
 
   ArmPkg/Drivers/ArmGic/ArmGicDxe.inf
   Platform/RaspberryPi/Drivers/RpiFirmwareDxe/RpiFirmwareDxe.inf
+!if $(ACPI_BASIC_MODE_ENABLE) == FALSE
   Platform/RaspberryPi/Drivers/FdtDxe/FdtDxe.inf
+!endif
   Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.inf
   ArmPkg/Drivers/TimerDxe/TimerDxe.inf
   MdeModulePkg/Universal/WatchdogTimerDxe/WatchdogTimer.inf
diff --git a/Platform/RaspberryPi/RPi4/RPi4.fdf b/Platform/RaspberryPi/RPi4/RPi4.fdf
index 50fe554ec9ec..2bcfdb3244f6 100644
--- a/Platform/RaspberryPi/RPi4/RPi4.fdf
+++ b/Platform/RaspberryPi/RPi4/RPi4.fdf
@@ -208,10 +208,13 @@ [FV.FvMain]
   INF MdeModulePkg/Universal/Console/TerminalDxe/TerminalDxe.inf
   INF MdeModulePkg/Universal/SerialDxe/SerialDxe.inf
   INF Platform/RaspberryPi/Drivers/DisplayDxe/DisplayDxe.inf
+  INF EmbeddedPkg/Drivers/ConsolePrefDxe/ConsolePrefDxe.inf
 
   INF ArmPkg/Drivers/ArmGic/ArmGicDxe.inf
   INF Platform/RaspberryPi/Drivers/RpiFirmwareDxe/RpiFirmwareDxe.inf
+!if $(ACPI_BASIC_MODE_ENABLE) == FALSE
   INF Platform/RaspberryPi/Drivers/FdtDxe/FdtDxe.inf
+!endif
   INF Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.inf
   INF ArmPkg/Drivers/TimerDxe/TimerDxe.inf
   INF MdeModulePkg/Universal/WatchdogTimerDxe/WatchdogTimer.inf
diff --git a/Platform/RaspberryPi/RPi4/Readme.md b/Platform/RaspberryPi/RPi4/Readme.md
index 2ef38d1b2062..83e901c57b08 100644
--- a/Platform/RaspberryPi/RPi4/Readme.md
+++ b/Platform/RaspberryPi/RPi4/Readme.md
@@ -16,8 +16,9 @@ Raspberry Pi is a trademark of the [Raspberry Pi Foundation](https://www.raspber
 This firmware is still in development stage, meaning that it comes with the
 following __major__ limitations:
 
-- USB is likely to work only in pre-OS phase at this stage (nonstandard ECAM,
-  missing ACPI tables).
+- USB may only work in pre-OS phase at this stage due to nonstandard ECAM,
+  missing/incomplete ACPI tables as well as other factors. For Linux, using
+  the `ACPI_BASIC_MODE_ENABLE` build option may help.
 - Serial I/O from the OS may not work due to CPU throttling affecting the
   miniUART baudrate. This can be worked around by using the `PL011_ENABLE`
   compilation option.
@@ -27,6 +28,10 @@ following __major__ limitations:
 Build instructions from the top level edk2-platforms Readme.md apply.
 
 The following additional build options are also available:
+- `-D ACPI_BASIC_MODE_ENABLE=1`: Limits OS visible memory to 3 GB and forces
+  ACPI (by disabling the Device Tree driver altogether). This may be required
+  to boot Operating Systems such as Linux on account of the current PCIe/xHCI
+  limitations.
 - `-D PL011_ENABLE=1`: Selects PL011 for the serial console instead of the
   miniUART (default). This doesn't change the GPIO pinout for the UART but
   can be useful if you find that the miniUART baud rate changes when the
diff --git a/Platform/RaspberryPi/RaspberryPi.dec b/Platform/RaspberryPi/RaspberryPi.dec
index c7e17350544a..bc378ffbfb8d 100644
--- a/Platform/RaspberryPi/RaspberryPi.dec
+++ b/Platform/RaspberryPi/RaspberryPi.dec
@@ -57,3 +57,6 @@ [PcdsFixedAtBuild, PcdsPatchableInModule, PcdsDynamic, PcdsDynamicEx]
   gRaspberryPiTokenSpaceGuid.PcdCustomCpuClock|0|UINT32|0x00000016
   gRaspberryPiTokenSpaceGuid.PcdDisplayEnableScaledVModes|0|UINT8|0x00000017
   gRaspberryPiTokenSpaceGuid.PcdDisplayEnableSShot|0|UINT32|0x00000018
+
+[PcdsFeatureFlag.common]
+  gRaspberryPiTokenSpaceGuid.PcdAcpiBasicMode|FALSE|BOOLEAN|0x00000019
-- 
2.21.0.windows.1