BGMAC_DMA_TX_CTL
bgmac_write(bgmac, ring->mmio_base + BGMAC_DMA_TX_CTL, ctl);
bgmac_write(bgmac, ring->mmio_base + BGMAC_DMA_TX_CTL,
bgmac_write(bgmac, ring->mmio_base + BGMAC_DMA_TX_CTL, 0);
ctl = bgmac_read(bgmac, ring->mmio_base + BGMAC_DMA_TX_CTL);