Fix reading and writing to mtimeh/mtimecmph on 64b Fabrics #15
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Example: li s0, (CLINT_BASE + MTIMEH_OFFSET) // 0x_xxxx_bffc lw t0, 4(s0) t0 won't get the correct value mkNear_Mem_IO.rl_process_rd_req properly puts the value in the low 4-bytes of rdata, however, MMU_Cache.rl_io_near_mem_read_rsp uses fn_extract_and_extend_bytes which extracts the upper 4-bytes of the returned rdata (assuming a 64-bit aligned AXI rdata is returned). The commit properly composes a read reponse as mkNear_Mem_IO.rl_process_rd_req expects.
Example: li s0, (CLINT_BASE + MTIMECMPH_OFFSET) // 0x_xxxx_4004 sw t0, 4(s0) MMU_Cache.fn_to_fabric_write_fields composes a 64-bit wdata assuming the waddr is always gonna be 64-bit aligned, and thus puts the requested_wdata in the upper 4-bytes of word64 with the corresponding 0xf0 strobe. mkNear_Mem_IO.rl_process_wr_req however, handles writes to 0xxxx_bffc/0xxxx_4004, expecting the wdata to contain the value in the LSB (lower 4 bytes). The commit fixes mkNear_Mem_IO.rl_process_wr_req to handle "SW" writes on 64b fabrics by extracting the upper 4-bytes set by MMU_Cache.fn_to_fabric_write_fields.
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