What is the difference between Exclusive access in AXI 3 and AXI 4 ?How does Lock access is merged to exclusive access in AXI4?
I don't think anything changed with the definitions of exclusive transactions when comparing AXI3 to AXI4. All that needed adding to the AXI4 description was that the maximum burst length used in an exclusive transfer was 16 (to cover where AXI4 supports non-exclusive INCR bursts longer than 16).
LOCKed transfers were not merged with exclusives in AXI4, they were simply no longer supported.
LOCKed transfers were removed because they could have a big impact on latency for other AXI managers who were unable to access the AXI subordinate being accessed by a LOCKed sequence, and if that LOCKed sequence was relatively long this could cause serious problems for other managers who might have higher importance. Instead exclusive transactions do allow other AXI managers to access the shared AXI subordinate, so don't affect their access latencies, but describe a process by which the subordinate can indicate if the target locations have been changed by another manager between the exclusive read and write transfers.