From f60dfe0c561a8f1b8e30d3770997cbaa636f57f9 Mon Sep 17 00:00:00 2001 From: Paul Cercueil Date: Fri, 15 Dec 2023 14:13:13 +0100 Subject: dmaengine: axi-dmac: Improve cyclic DMA transfers in SG mode For cyclic transfers, chain the last descriptor to the first one, and disable IRQ generation if there is no callback registered with the cyclic transfer. Signed-off-by: Paul Cercueil Link: https://lore.kernel.org/r/20231215131313.23840-6-paul@crapouillou.net Signed-off-by: Vinod Koul --- drivers/dma/dma-axi-dmac.c | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-) (limited to 'drivers/dma/dma-axi-dmac.c') diff --git a/drivers/dma/dma-axi-dmac.c b/drivers/dma/dma-axi-dmac.c index f63acae511fb..4e339c04fc1e 100644 --- a/drivers/dma/dma-axi-dmac.c +++ b/drivers/dma/dma-axi-dmac.c @@ -285,12 +285,14 @@ static void axi_dmac_start_transfer(struct axi_dmac_chan *chan) /* * If the hardware supports cyclic transfers and there is no callback to - * call and only a single segment, enable hw cyclic mode to avoid - * unnecessary interrupts. + * call, enable hw cyclic mode to avoid unnecessary interrupts. */ - if (chan->hw_cyclic && desc->cyclic && !desc->vdesc.tx.callback && - desc->num_sgs == 1) - flags |= AXI_DMAC_FLAG_CYCLIC; + if (chan->hw_cyclic && desc->cyclic && !desc->vdesc.tx.callback) { + if (chan->hw_sg) + desc->sg[desc->num_sgs - 1].hw->flags &= ~AXI_DMAC_HW_FLAG_IRQ; + else if (desc->num_sgs == 1) + flags |= AXI_DMAC_FLAG_CYCLIC; + } if (chan->hw_partial_xfer) flags |= AXI_DMAC_FLAG_PARTIAL_REPORT; @@ -411,7 +413,6 @@ static bool axi_dmac_transfer_done(struct axi_dmac_chan *chan, if (chan->hw_sg) { if (active->cyclic) { vchan_cyclic_callback(&active->vdesc); - start_next = true; } else { list_del(&active->vdesc.node); vchan_cookie_complete(&active->vdesc); @@ -667,7 +668,7 @@ static struct dma_async_tx_descriptor *axi_dmac_prep_dma_cyclic( { struct axi_dmac_chan *chan = to_axi_dmac_chan(c); struct axi_dmac_desc *desc; - unsigned int num_periods, num_segments; + unsigned int num_periods, num_segments, num_sgs; if (direction != chan->direction) return NULL; @@ -681,11 +682,16 @@ static struct dma_async_tx_descriptor *axi_dmac_prep_dma_cyclic( num_periods = buf_len / period_len; num_segments = DIV_ROUND_UP(period_len, chan->max_length); + num_sgs = num_periods * num_segments; - desc = axi_dmac_alloc_desc(chan, num_periods * num_segments); + desc = axi_dmac_alloc_desc(chan, num_sgs); if (!desc) return NULL; + /* Chain the last descriptor to the first, and remove its "last" flag */ + desc->sg[num_sgs - 1].hw->next_sg_addr = desc->sg[0].hw_phys; + desc->sg[num_sgs - 1].hw->flags &= ~AXI_DMAC_HW_FLAG_LAST; + axi_dmac_fill_linear_sg(chan, direction, buf_addr, num_periods, period_len, desc->sg); -- cgit v1.2.3