1. A method of data processing in a cache memory, said method comprising: caching a plurality of cache lines of data in a corresponding plurality of entries in a cache array, each of the plurality of cache lines including multiple data granules; for each of the plurality of cache entries, indicating in a respective one of a plurality of line coherency state fields an associated coherency state applicable to two or more data granules; and for at least a particular cache line among the plurality of cache lines, implementing a granule coherency state field that indicates a coherency state for a particular granule of the multiple data granules in the particular cache line, wherein the coherency state indicated by the granule coherency state field differs from that indicated for the particular cache line by its line coherency state field.