mmDMA_GFX_RB_CNTL
rb_cntl = RREG32(mmDMA_GFX_RB_CNTL + sdma_offsets[i]);
WREG32(mmDMA_GFX_RB_CNTL + sdma_offsets[i], rb_cntl);
WREG32(mmDMA_GFX_RB_CNTL + sdma_offsets[i], rb_cntl);
WREG32(mmDMA_GFX_RB_CNTL + sdma_offsets[i], rb_cntl | DMA_GFX_RB_CNTL__RB_ENABLE_MASK);