Add hst_block_db to enable smbus block_reads

Signed-off-by: Nathaniel Mitchell <nathaniel.p.mitchell@intel.com>

Author: npmitche

chipsec/cfg/8086/SMBUS/smbus1.xml

@@ -80,6 +80,9 @@
         <register name="HST_D1" type="iobar" bar="SMBUS_BASE" offset="0x06" size="1" desc="SMBus Host Data 1">
             <field name="Data"         bit="0" size="8" desc="Data1" />
         </register>
+        <register name="HST_BLOCK_DB" type="iobar" bar="SMBUS_BASE" offset="0x07" size="1" desc="SMBus Host Block Data">
+            <field name="BDTA"         bit="0" size="8" desc="Block Data" />
+        </register>
 
         <!-- PCH TCOBASE (SMBus TCO) I/O registers -->
         <register name="TCO1_CNT" type="iobar" bar="TCOBASE" offset="0x8" size="2" desc="TCO1 Control">

chipsec/library/bits.py

@@ -126,8 +126,11 @@ def get_bits(value: int, field_bit: int, size: int, preserve_field_position: Opt
 
 
 
-def set_bits(bit: int, size: int, initial_value: int, value: int) -> int:
+def set_bits(bit: int, size: int, initial_value: int, value: int, preserve_field_position: Optional[bool] = False) -> int:
     field_mask = make_mask(size)
     new_value = initial_value & ~(field_mask << bit)
-    new_value |= ((value & field_mask) << bit)
+    if preserve_field_position:
+        new_value |= (value & (field_mask << bit))
+    else:
+        new_value |= ((value & field_mask) << bit)
     return new_value

chipsec/library/register.py

@@ -484,12 +484,12 @@ def get_instance(self) -> Any:
     def set_value(self, value: int) -> None:
         self.value = value
 
-    def set_field(self, field_name: str, field_value: int) -> int:
+    def set_field(self, field_name: str, field_value: int, preserve_field_position: Optional[bool] = False) -> int:
         field_name = field_name.upper()
         field_attrs = self.fields[field_name]
         bit = field_attrs['bit']
         size = field_attrs['size']
-        self.value = set_bits(bit, size, self.value, field_value)
+        self.value = set_bits(bit, size, self.value, field_value, preserve_field_position)
         return self.value
 
     def get_field(
@@ -526,13 +526,13 @@ def get_field_mask(
         return mask
 
     def write_field(
-        self, field_name: str, field_value: int, update_value: bool = False
+        self, field_name: str, field_value: int, update_value: bool = False, preserve_field_position: Optional[bool] = False
     ) -> None:
         if update_value or self.value is None:
             if self.value is None:
                 self.logger.log_debug(f'Value is None for {self.name}. Reading value')
             self.read()
-        new_value = self.set_field(field_name, field_value)
+        new_value = self.set_field(field_name, field_value, preserve_field_position)
         self.write(new_value)
 
     def read_field(