why the "replace_req" should depend on (buffer_empty & write_ack_i)?

[adonics]

Hi SIr
// back-end read channel
assign replace_req_o = (~hit & read_access & ~replace_i) & (buffer_empty & write_ack_i); //write-through policy

It is said write-through doesn't adopt write allocate, why the "replace_req" should depend on (buffer_empty & write_ack_i)?
best regards
adonics

[jjts]

If the buffer is not empty, you can't guarantee that you are reading the last updated data. It prevents the cache line from being replaced with an old line.

[adonics]

thx, I try to understand that

• if last beat is a write, ack_o will assert when ~buffer_full&write_access, then host can launch next req
• when next req is a read and miss, the controller want to issue a replace, but he need make sure that previous write data/strb really go out