[PATCH v4 2/6] Platform/RaspberryPi: Monitor ACPI Table installs

["Jeremy Linton" <jeremy.linton@arm.com>]

Hook the ACPI table install sequence and add some
basic conditional and AML NameOp update logic. If
a table has a non-zero PCD declared that pcd is
checked for a non-zero value before allowing the table
to be installed. We also add a table of NameOp to
PCD's which will be written into a DSDT/SSDT table
as part of its install process.

With this change we can declare something in
ASL like:

Name (VARN, 0x1234)

and then add a table entry like:

{"VARN", PcdToken(PcdVarn)}

and the value of PcdVarn will replace the
0x1234 declared in the ASL above.

Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Pete Batard <pete@akeo.ie>
Cc: Andrei Warkentin <awarkentin@vmware.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Samer El-Haj-Mahmoud <Samer.El-Haj-Mahmoud@arm.com>
Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Reviewed-by: Pete Batard <@pbatard>
---
 Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c | 153 ++++++++++++++++++++-
 1 file changed, 152 insertions(+), 1 deletion(-)

diff --git a/Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c b/Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c
index af54136ade..9e5d9734ca 100644
--- a/Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c
+++ b/Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c
@@ -568,6 +568,156 @@ ApplyVariables (
 }
 
 
+typedef struct {
+  CHAR8 Name[4];
+  UINTN PcdToken;
+} AML_NAME_OP_REPLACE;
+
+typedef struct {
+  UINT64              OemTableId;
+  UINTN               PcdToken;
+  AML_NAME_OP_REPLACE *SdtNameOpReplace;
+} NAMESPACE_TABLES;
+
+#define SSDT_PATTERN_LEN 5
+#define AML_NAMEOP_8   0x0A
+#define AML_NAMEOP_16  0x0B
+#define AML_NAMEOP_32  0x0C
+#define AML_NAMEOP_STR 0x0D
+/*
+ * Scan the given namespace table (DSDT/SSDT) for AML NameOps
+ * listed in the NameOpReplace structure. If one is found then
+ * update the value in the table from the specified Pcd
+ *
+ * This allows us to have conditionals in AML controlled
+ * by options in the BDS or detected during firmware bootstrap.
+ * We could extend this concept for strings/etc but due to len
+ * variations its probably easier to encode the strings
+ * in the ASL and pick the correct one based off a variable.
+ */
+STATIC VOID
+UpdateSdtNameOps(
+  EFI_ACPI_DESCRIPTION_HEADER  *AcpiTable,
+  AML_NAME_OP_REPLACE          *NameOpReplace
+  )
+{
+  UINTN  Idx;
+  UINTN  Index;
+  CHAR8  Pattern[SSDT_PATTERN_LEN];
+  UINTN  PcdVal;
+  UINT8  *SdtPtr;
+  UINT32 SdtSize;
+
+  SdtSize = AcpiTable->Length;
+
+  if (SdtSize > 0) {
+    SdtPtr = (UINT8*)AcpiTable;
+
+    for (Idx = 0; NameOpReplace && NameOpReplace[Idx].PcdToken; Idx++) {
+      /*
+       * Do a single NameOp variable replacement these are of the
+       * form 08 XXXX SIZE VAL, where SIZE is 0A=byte, 0B=word, 0C=dword
+       * and XXXX is the name and VAL is the value
+      */
+      Pattern[0] = 0x08;
+      Pattern[1] = NameOpReplace[Idx].Name[0];
+      Pattern[2] = NameOpReplace[Idx].Name[1];
+      Pattern[3] = NameOpReplace[Idx].Name[2];
+      Pattern[4] = NameOpReplace[Idx].Name[3];
+
+      for (Index = 0; Index < (SdtSize - SSDT_PATTERN_LEN); Index++) {
+        if (CompareMem (SdtPtr + Index, Pattern, SSDT_PATTERN_LEN) == 0) {
+          PcdVal = LibPcdGet32 (NameOpReplace[Idx].PcdToken);
+          switch (SdtPtr[Index + SSDT_PATTERN_LEN]) {
+          case AML_NAMEOP_32:
+            SdtPtr[Index + SSDT_PATTERN_LEN + 4] = (PcdVal >> 24) & 0xFF;
+            SdtPtr[Index + SSDT_PATTERN_LEN + 3] = (PcdVal >> 16) & 0xFF;
+            // Fallthrough
+          case AML_NAMEOP_16:
+            SdtPtr[Index + SSDT_PATTERN_LEN + 2] = (PcdVal >> 8) & 0xFF;
+            // Fallthrough
+          case AML_NAMEOP_8:
+            SdtPtr[Index + SSDT_PATTERN_LEN + 1] = PcdVal & 0xFF;
+            break;
+          case 0:
+          case 1:
+            SdtPtr[Index + SSDT_PATTERN_LEN + 1] = !!PcdVal;
+            break;
+          case AML_NAMEOP_STR:
+            /*
+             * If the string val is added to the NameOpReplace, we can
+             * dynamically update things like _HID too as long as the
+             * string length matches.
+             */
+            break;
+          }
+          break;
+        }
+      }
+    }
+  }
+}
+
+
+STATIC BOOLEAN
+VerifyUpdateTable(
+  IN  EFI_ACPI_DESCRIPTION_HEADER *AcpiHeader,
+  IN  NAMESPACE_TABLES *SdtTable
+  )
+{
+  BOOLEAN ret;
+
+  ret = TRUE;
+  if (SdtTable->PcdToken && !LibPcdGet32 (SdtTable->PcdToken)) {
+    ret = FALSE;
+  }
+  if (ret && SdtTable->SdtNameOpReplace) {
+    UpdateSdtNameOps (AcpiHeader, SdtTable->SdtNameOpReplace);
+  }
+
+  return ret;
+}
+
+
+STATIC NAMESPACE_TABLES SdtTables[] = {
+  {
+    SIGNATURE_64 ('R', 'P', 'I', 0, 0, 0, 0, 0),
+    0,
+    NULL
+  },
+  { }
+};
+
+/*
+ * Monitor the ACPI tables being installed and when
+ * a DSDT/SSDT is detected validate that we want to
+ * install it, and if so update any "NameOp" defined
+ * variables contained in the table from PCD values
+ */
+STATIC BOOLEAN
+HandleDynamicNamespace (
+  IN  EFI_ACPI_DESCRIPTION_HEADER *AcpiHeader
+  )
+{
+  UINTN Tables;
+
+  switch (AcpiHeader->Signature) {
+  case SIGNATURE_32 ('D', 'S', 'D', 'T'):
+  case SIGNATURE_32 ('S', 'S', 'D', 'T'):
+    for (Tables = 0; SdtTables[Tables].OemTableId; Tables++) {
+      if (AcpiHeader->OemTableId == SdtTables[Tables].OemTableId) {
+        return VerifyUpdateTable (AcpiHeader, &SdtTables[Tables]);
+      }
+    }
+    DEBUG ((DEBUG_ERROR, "Found namespace table not in table list.\n"));
+
+    return FALSE;
+  }
+
+  return TRUE;
+}
+
+
 EFI_STATUS
 EFIAPI
 ConfigInitialize (
@@ -618,7 +768,8 @@ ConfigInitialize (
 
   if (PcdGet32 (PcdSystemTableMode) == SYSTEM_TABLE_MODE_ACPI ||
       PcdGet32 (PcdSystemTableMode) == SYSTEM_TABLE_MODE_BOTH) {
-     Status = LocateAndInstallAcpiFromFv (&mAcpiTableFile);
+     Status = LocateAndInstallAcpiFromFvConditional (&mAcpiTableFile,
+                                                     &HandleDynamicNamespace);
      ASSERT_EFI_ERROR (Status);
   }
 
-- 
2.13.7