On 18-01-19, 11:10, Long Cheng wrote: > +static enum dma_status mtk_uart_apdma_tx_status(struct dma_chan *chan, > + dma_cookie_t cookie, > + struct dma_tx_state *txstate) > +{ > + struct mtk_chan *c = to_mtk_uart_apdma_chan(chan); > + enum dma_status ret; > + unsigned long flags; > + > + if (!txstate) > + return DMA_ERROR; Why, it is not a mandatory arg! > + ret = dma_cookie_status(chan, cookie, txstate); > + spin_lock_irqsave(&c->vc.lock, flags); > + if (ret == DMA_IN_PROGRESS) { > + c->rx_status = mtk_uart_apdma_read(c, VFF_RPT) & VFF_RING_SIZE; > + dma_set_residue(txstate, c->rx_status); > + } else if (ret == DMA_COMPLETE && c->dir == DMA_DEV_TO_MEM) { > + dma_set_residue(txstate, c->rx_status); what is the point is setting residue to comleted txn, it is zero! > + } else { > + dma_set_residue(txstate, 0); naah that doesnt sound correct! > +static void mtk_uart_apdma_config_write(struct dma_chan *chan, > + struct dma_slave_config *cfg, > + enum dma_transfer_direction dir) > +{ > + struct mtk_chan *c = to_mtk_uart_apdma_chan(chan); > + struct mtk_uart_apdmadev *mtkd = > + to_mtk_uart_apdma_dev(c->vc.chan.device); > + unsigned int tmp; > + > + if (mtk_uart_apdma_read(c, VFF_EN) == VFF_EN_B) > + return; > + > + c->dir = dir; > + > + if (dir == DMA_DEV_TO_MEM) { > + tmp = cfg->src_addr_width * 1024; why multiply by 1024? > +static int mtk_uart_apdma_device_pause(struct dma_chan *chan) > +{ > + /* just for check caps pass */ > + return 0; > +} please remove, this is not a mandatory fn -- ~Vinod