hws_write_if_diff
hws_write_if_diff(hws, HWS_REG_OUT_RES(ch), want_out_res);
hws_write_if_diff(hws, HWS_REG_BCHS(ch), packed);
hws_write_if_diff(pdx, HWS_REG_OUT_RES(ch), (h << 16) | w);