When generating _CPC objects, some fields are mandatory by spec [1].
Some fields cannot be supported by a the Juno platform, which is used
to test the _CPC generation. Therefore, don't prevent the generation
of _CPC objects if the fields below are missing, and let the OS handle
the missing information.

_CPC fields that are exempted from checks:
- PerformanceLimitedRegister
- ReferencePerformanceCounterRegister
- DeliveredPerformanceCounterRegister

Also warn if one of the following optional fields is missing:
- HighestPerformance[Buffer|Integer]
- NominalPerformance[Buffer|Integer]

[1] Cf. non-optional fields in:
    ACPI 6.5, s8.4.6.1 '_CPC (Continuous Performance Control)'

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
---
 .../Common/AmlLib/CodeGen/AmlCodeGen.c        | 29 ++++++++++++++++---
 1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/DynamicTablesPkg/Library/Common/AmlLib/CodeGen/AmlCodeGen.c b/DynamicTablesPkg/Library/Common/AmlLib/CodeGen/AmlCodeGen.c
index a96d2b8a048a..9b72c4408016 100644
--- a/DynamicTablesPkg/Library/Common/AmlLib/CodeGen/AmlCodeGen.c
+++ b/DynamicTablesPkg/Library/Common/AmlLib/CodeGen/AmlCodeGen.c
@@ -3531,6 +3531,21 @@ AmlCreateCpcNode (
     return EFI_INVALID_PARAMETER;
   }
 
+  // The following fields are theoretically mandatory, but not supported
+  // by some platforms. Just warn if they are missing:
+  // - PerformanceLimitedRegister
+  // - ReferencePerformanceCounterRegister
+  // - DeliveredPerformanceCounterRegister
+  if (IsNullGenericAddress (&CpcInfo->PerformanceLimitedRegister) ||
+      IsNullGenericAddress (&CpcInfo->ReferencePerformanceCounterRegister) ||
+      IsNullGenericAddress (&CpcInfo->DeliveredPerformanceCounterRegister)) {
+    DEBUG ((
+      DEBUG_WARN,
+      "Missing PerformanceLimited|ReferencePerformanceCounter|"
+      "DeliveredPerformanceCounter field in _CPC object\n"
+      ));
+  }
+
   if ((IsNullGenericAddress (&CpcInfo->HighestPerformanceBuffer) &&
        (CpcInfo->HighestPerformanceInteger == 0)) ||
       (IsNullGenericAddress (&CpcInfo->NominalPerformanceBuffer) &&
@@ -3539,13 +3554,19 @@ AmlCreateCpcNode (
        (CpcInfo->LowestNonlinearPerformanceInteger == 0)) ||
       (IsNullGenericAddress (&CpcInfo->LowestPerformanceBuffer) &&
        (CpcInfo->LowestPerformanceInteger == 0)) ||
-      IsNullGenericAddress (&CpcInfo->DesiredPerformanceRegister) ||
-      IsNullGenericAddress (&CpcInfo->ReferencePerformanceCounterRegister) ||
-      IsNullGenericAddress (&CpcInfo->DeliveredPerformanceCounterRegister) ||
-      IsNullGenericAddress (&CpcInfo->PerformanceLimitedRegister))
+      IsNullGenericAddress (&CpcInfo->DesiredPerformanceRegister))
   {
     ASSERT (0);
     return EFI_INVALID_PARAMETER;
+  } else if ((IsNullGenericAddress (&CpcInfo->HighestPerformanceBuffer) &&
+              (CpcInfo->HighestPerformanceInteger == 0)) ||
+             (IsNullGenericAddress (&CpcInfo->NominalPerformanceBuffer) &&
+              (CpcInfo->NominalPerformanceInteger == 0)))
+  {
+    DEBUG ((
+      DEBUG_WARN,
+      "Missing Reference|Delivered performance field in _CPC object\n"
+      ));
   }
 
   CpcPackage = NULL;
-- 
2.25.1



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