From 88987d2c7534a0269f567fb101e6d71a08f0f01d Mon Sep 17 00:00:00 2001 From: Robert Baldyga Date: Wed, 11 Feb 2015 13:23:18 +0100 Subject: dmaengine: pl330: add DMA_PAUSE feature DMA_PAUSE command is used for halting DMA transfer on chosen channel. It can be useful when we want to safely read residue before terminating all requests on channel. Otherwise there can be situation when some data is transferred before channel termination but after reading residue, which obviously results with data loss. To avoid this situation we can pause channel, read residue and then terminate all requests. This scenario is common, for example, in serial port drivers. Signed-off-by: Robert Baldyga Signed-off-by: Vinod Koul --- drivers/dma/pl330.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c index 944b67622916..0e1f56772855 100644 --- a/drivers/dma/pl330.c +++ b/drivers/dma/pl330.c @@ -2155,6 +2155,33 @@ static int pl330_terminate_all(struct dma_chan *chan) return 0; } +/* + * We don't support DMA_RESUME command because of hardware + * limitations, so after pausing the channel we cannot restore + * it to active state. We have to terminate channel and setup + * DMA transfer again. This pause feature was implemented to + * allow safely read residue before channel termination. + */ +int pl330_pause(struct dma_chan *chan) +{ + struct dma_pl330_chan *pch = to_pchan(chan); + struct pl330_dmac *pl330 = pch->dmac; + unsigned long flags; + + pm_runtime_get_sync(pl330->ddma.dev); + spin_lock_irqsave(&pch->lock, flags); + + spin_lock(&pl330->lock); + _stop(pch->thread); + spin_unlock(&pl330->lock); + + spin_unlock_irqrestore(&pch->lock, flags); + pm_runtime_mark_last_busy(pl330->ddma.dev); + pm_runtime_put_autosuspend(pl330->ddma.dev); + + return 0; +} + static void pl330_free_chan_resources(struct dma_chan *chan) { struct dma_pl330_chan *pch = to_pchan(chan); @@ -2842,6 +2869,7 @@ pl330_probe(struct amba_device *adev, const struct amba_id *id) pd->device_tx_status = pl330_tx_status; pd->device_prep_slave_sg = pl330_prep_slave_sg; pd->device_config = pl330_config; + pd->device_pause = pl330_pause; pd->device_terminate_all = pl330_terminate_all; pd->device_issue_pending = pl330_issue_pending; pd->src_addr_widths = PL330_DMA_BUSWIDTHS; -- cgit v1.2.1