diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c index ca396b709742..6e7b183cb499 100644 --- a/drivers/dma/xilinx/xilinx_dma.c +++ b/drivers/dma/xilinx/xilinx_dma.c @@ -1580,7 +1580,14 @@ static void xilinx_dma_start_transfer(struct xilinx_dma_chan *chan) return; } - if (!chan->idle) + /* + * Direct (non-SG) mode has no descriptor queue: writing the BTT + * register launches a transfer immediately, so a new transfer must + * not be programmed while one is in flight. Keep such transfers + * serialized. SG mode supports chaining onto a running transfer via + * tail-pointer extension, so it is allowed to proceed when busy. + */ + if (!chan->has_sg && !chan->idle) return; head_desc = list_first_entry(&chan->pending_list, @@ -1599,7 +1606,7 @@ static void xilinx_dma_start_transfer(struct xilinx_dma_chan *chan) dma_ctrl_write(chan, XILINX_DMA_REG_DMACR, reg); } - if (chan->has_sg) + if (chan->has_sg && list_empty(&chan->active_list)) xilinx_write(chan, XILINX_DMA_REG_CURDESC, head_desc->async_tx.phys); reg &= ~XILINX_DMA_CR_DELAY_MAX; @@ -1660,9 +1667,6 @@ static void xilinx_mcdma_start_transfer(struct xilinx_dma_chan *chan) if (chan->err) return; - if (!chan->idle) - return; - if (list_empty(&chan->pending_list)) return; @@ -1685,8 +1689,9 @@ static void xilinx_mcdma_start_transfer(struct xilinx_dma_chan *chan) dma_ctrl_write(chan, XILINX_MCDMA_CHAN_CR_OFFSET(chan->tdest), reg); /* Program current descriptor */ - xilinx_write(chan, XILINX_MCDMA_CHAN_CDESC_OFFSET(chan->tdest), - head_desc->async_tx.phys); + if (chan->has_sg && list_empty(&chan->active_list)) + xilinx_write(chan, XILINX_MCDMA_CHAN_CDESC_OFFSET(chan->tdest), + head_desc->async_tx.phys); /* Program channel enable register */ reg = dma_ctrl_read(chan, XILINX_MCDMA_CHEN_OFFSET);