[PATCH v3 07/24] dmaengine: dw-edma: Centralize LL doorbell decisions

[Koichiro Den]

LL fill currently rings the doorbell every time. A running eDMA or HDMA
channel follows entries whose CB matches CCS without another kick. A
channel stopped at a CB mismatch needs one.

Move that decision to dw_edma_core_ch_maybe_doorbell(). It rings only
for a BUSY LL channel with pending entries, no EDMA_REQ_STOP or
EDMA_REQ_PAUSE. The BUSY check prevents EDMA_REQ_STOP completion from
restarting terminated work.

issue_pending() still publishes LL entries only from IDLE. A later patch
allows live appends. Non-LL channels are unchanged.

Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>
---
Changes in v3:
  - Keep status gating out of this preparatory change. Add it together with
    the stopped-tail recheck. (Sashiko)

 drivers/dma/dw-edma/dw-edma-core.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
index b419ff2becf9..c036510dabcb 100644
--- a/drivers/dma/dw-edma/dw-edma-core.c
+++ b/drivers/dma/dw-edma/dw-edma-core.c
@@ -167,8 +167,6 @@ static void dw_edma_core_ll_start(struct dw_edma_desc *desc)
 
 	desc->done_burst = desc->start_burst;
 	desc->start_burst = i;
-
-	dw_edma_core_ch_doorbell(chan);
 }
 
 static void dw_edma_core_start(struct dw_edma_desc *desc)
@@ -249,6 +247,16 @@ static void dw_edma_finish_termination(struct dw_edma_chan *chan)
 	chan->status = EDMA_ST_IDLE;
 }
 
+/* Must be called with vc.lock held. */
+static void dw_edma_core_ch_maybe_doorbell(struct dw_edma_chan *chan)
+{
+	if (chan->non_ll || chan->request != EDMA_REQ_NONE ||
+	    chan->status != EDMA_ST_BUSY || !dw_edma_ll_pending(chan))
+		return;
+
+	dw_edma_core_ch_doorbell(chan);
+}
+
 static void dw_edma_device_caps(struct dma_chan *dchan,
 				struct dma_slave_caps *caps)
 {
@@ -374,6 +382,7 @@ static int dw_edma_device_resume(struct dma_chan *dchan)
 		chan->status = EDMA_ST_BUSY;
 		if (!dw_edma_start_transfer(chan))
 			chan->status = EDMA_ST_IDLE;
+		dw_edma_core_ch_maybe_doorbell(chan);
 	}
 
 	return err;
@@ -420,6 +429,7 @@ static void dw_edma_device_issue_pending(struct dma_chan *dchan)
 	    chan->status == EDMA_ST_IDLE) {
 		chan->status = EDMA_ST_BUSY;
 		dw_edma_start_transfer(chan);
+		dw_edma_core_ch_maybe_doorbell(chan);
 	}
 	spin_unlock_irqrestore(&chan->vc.lock, flags);
 }
@@ -733,6 +743,8 @@ static void dw_edma_done_interrupt(struct dw_edma_chan *chan)
 	default:
 		break;
 	}
+	dw_edma_core_ch_maybe_doorbell(chan);
+
 	spin_unlock_irqrestore(&chan->vc.lock, flags);
 }
 
-- 
2.51.0