Out of order sgl read sorting in a mixed system with prp read or system that supports only sgl reads

Abstract

A data storage device includes a non-volatile semiconductor storage device and a controller that is configured to issue first and second read requests in that order, to read data from the non-volatile semiconductor storage device, in response to receiving a read command, and store read responses to the first and second read requests in a queue in the order they are received. The queue is a circular buffer having a write pointer, a read pointer, and a special read pointer associated therewith, the write pointer being advanced each time contents are written into the buffer, the read pointer being advanced when oldest valid contents in the buffer are read, and the special read pointer being advanced when valid contents in the buffer, excluding the oldest valid contents, are read. As a result, instead of sorting read responses associated with the read command prior to storing them in the queue, the read responses are stored in the queue in the order they are received.