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authorRobert Baldyga <r.baldyga@samsung.com>2015-02-11 13:23:18 +0100
committerVinod Koul <vinod.koul@intel.com>2015-02-16 09:33:36 +0530
commit88987d2c7534a0269f567fb101e6d71a08f0f01d (patch)
treec9305c6ff9b11138f51889126e15f55af2b4350c
parentaee4d1fac887252faf6f7caf7bf1616131d5dbcd (diff)
downloadblackbird-obmc-linux-88987d2c7534a0269f567fb101e6d71a08f0f01d.tar.gz
blackbird-obmc-linux-88987d2c7534a0269f567fb101e6d71a08f0f01d.zip
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 <r.baldyga@samsung.com> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
-rw-r--r--drivers/dma/pl330.c28
1 files changed, 28 insertions, 0 deletions
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;
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