mmDMA_GFX_RB_WPTR
WREG32(mmDMA_GFX_RB_WPTR + sdma_offsets[i], 0);
WREG32(mmDMA_GFX_RB_WPTR + sdma_offsets[i], ring->wptr << 2);
return (RREG32(mmDMA_GFX_RB_WPTR + sdma_offsets[me]) & 0x3fffc) >> 2;
WREG32(mmDMA_GFX_RB_WPTR + sdma_offsets[me], (ring->wptr << 2) & 0x3fffc);