enable prefetch drop for better MC fairness

Change-Id: I45f9a126102ff519866a794a76deef780a92a97b
Original-Change-Id: I0fee2fe19b703e090ad2364a2a38dac31079b38f
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/37010
Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com>
Tested-by: PPE CI <ppe-ci+hostboot@us.ibm.com>
Reviewed-by: Kevin F. Reick <reick@us.ibm.com>
Reviewed-by: Jenny Huynh <jhuynh@us.ibm.com>
Tested-by: Hostboot CI <hostboot-ci+hostboot@us.ibm.com>
Reviewed-by: Joseph J. McGill <jmcgill@us.ibm.com>
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/55474
CI-Ready: Daniel M. Crowell <dcrowell@us.ibm.com>
Reviewed-by: Daniel M. Crowell <dcrowell@us.ibm.com>
Tested-by: Daniel M. Crowell <dcrowell@us.ibm.com>

src/import/chips/p9/procedures/xml/attribute_info/chip_ec_attributes.xml

@@ -2319,7 +2319,7 @@
   </attribute>
 
   <attribute>
-    <id>ATTR_CHIP_EC_FEATURE_HW40075</id>
+    <id>ATTR_CHIP_EC_FEATURE_HW400075</id>
     <targetType>TARGET_TYPE_PROC_CHIP</targetType>
     <description>
       Addresses issue where MDI bit was getting wrong values with threadmill and transactional data resulting in coherency issues.
@@ -2335,6 +2335,23 @@
     </chipEcFeature>
   </attribute>
 
+  <attribute>
+    <id>ATTR_CHIP_EC_FEATURE_HW398139</id>
+    <targetType>TARGET_TYPE_PROC_CHIP</targetType>
+    <description>
+      Avoid powerbus early hangs by enabling prefetch drops to break out of fairness issue with prefetch ops
+    </description>
+    <chipEcFeature>
+      <chip>
+        <name>ENUM_ATTR_NAME_NIMBUS</name>
+        <ec>
+          <value>0x20</value>
+          <test>LESS_THAN</test>
+        </ec>
+      </chip>
+    </chipEcFeature>
+  </attribute>
+
   <attribute>
     <id>ATTR_CHIP_EC_FEATURE_MSS_TRAINING_BAD_BITS</id>
     <targetType>TARGET_TYPE_PROC_CHIP</targetType>