• Mike Frysinger's avatar
    Blackfin: dpmc: optimize hibernate/resume path · eed7b836
    Mike Frysinger authored
    The current save logic used in hibernation is to do a MMR load (base +
    offset) into a register, and then push that onto the stack.  Then when
    restoring, pop off the stack into a register followed by a MMR store
    (base + offset).  These use plenty of 32bit insns rather than 16bit,
    are pretty long winded, and full of pipeline bubbles.
    
    So, by taking advantage of MMRs that are contiguous, the multi-register
    push/pop insn, and register abuse, we can shrink this code considerably.
    
    When saving, the new logic does a lot of loads into the data and pointer
    registers before executing a single multi-register push insn.  Then when
    restoring, we do a single multi-register pop insn followed by a lot of
    stores.  Overall, this allows us to cut the insn count by ~30%, the code
    size by ~45%, and drastically reduce the register hazards that trigger
    bubbles in the pipeline.
    Signed-off-by: default avatarMike Frysinger <vapier@gentoo.org>
    eed7b836
dpmc_modes.S 17.9 KB