Re: [PATCH v2 2/2] dmaengine: ti: omap-dma: Improved memcpy polling support

On 25/07/2019 16.37, Vinod Koul wrote:

On 16-07-19, 11:24, Peter Ujfalusi wrote:

quoted

When a DMA client driver does not set the DMA_PREP_INTERRUPT because it
does not want to use interrupts for DMA completion or because it can not
rely on DMA interrupts due to executing the memcpy when interrupts are
disabled it will poll the status of the transfer.

If the interrupts are enabled then the cookie will be set completed in the
interrupt handler so only check in HW completion when the polling is really
needed.

Signed-off-by: Peter Ujfalusi <redacted>
---
 drivers/dma/ti/omap-dma.c | 44 +++++++++++++++++++++++++--------------
 1 file changed, 28 insertions(+), 16 deletions(-)

diff --git a/drivers/dma/ti/omap-dma.c b/drivers/dma/ti/omap-dma.c
index 029c0bd550d5..966d8f0323b5 100644
--- a/drivers/dma/ti/omap-dma.c
+++ b/drivers/dma/ti/omap-dma.c

@@ -91,6 +91,7 @@ struct omap_desc {
 	bool using_ll;
 	enum dma_transfer_direction dir;
 	dma_addr_t dev_addr;
+	bool polled;
 
 	int32_t fi;		/* for OMAP_DMA_SYNC_PACKET / double indexing */
 	int16_t ei;		/* for double indexing */

@@ -815,26 +816,20 @@ static enum dma_status omap_dma_tx_status(struct dma_chan *chan,
 	struct virt_dma_desc *vd;
 	enum dma_status ret;
 	unsigned long flags;
+	struct omap_desc *d = NULL;
 
 	ret = dma_cookie_status(chan, cookie, txstate);
-
-	if (!c->paused && c->running) {
-		uint32_t ccr = omap_dma_chan_read(c, CCR);
-		/*
-		 * The channel is no longer active, set the return value
-		 * accordingly
-		 */
-		if (!(ccr & CCR_ENABLE))
-			ret = DMA_COMPLETE;
-	}
-
-	if (ret == DMA_COMPLETE || !txstate)
+	if (ret == DMA_COMPLETE)

why do you want to continue for txstate being null?

The caller could opt to not provide txstate and I still need to check if
the non completed transfer is actually done by the HW or not.

Also it would lead to NULL ptr deref for txstate

There is a !txstate check to avoid that.

quoted

 		return ret;
 
 	spin_lock_irqsave(&c->vc.lock, flags);
+	if (c->desc && c->desc->vd.tx.cookie == cookie)
+		d = c->desc;
+
+	if (!txstate)
+		goto out;
 
-	if (c->desc && c->desc->vd.tx.cookie == cookie) {
-		struct omap_desc *d = c->desc;
+	if (d) {
 		dma_addr_t pos;
 
 		if (d->dir == DMA_MEM_TO_DEV)

@@ -851,8 +846,22 @@ static enum dma_status omap_dma_tx_status(struct dma_chan *chan,
 		txstate->residue = 0;
 	}
 
-	if (ret == DMA_IN_PROGRESS && c->paused)
+out:
+	if (ret == DMA_IN_PROGRESS && c->paused) {
 		ret = DMA_PAUSED;
+	} else if (d && d->polled && c->running) {
+		uint32_t ccr = omap_dma_chan_read(c, CCR);
+		/*
+		 * The channel is no longer active, set the return value
+		 * accordingly and mark it as completed
+		 */
+		if (!(ccr & CCR_ENABLE)) {
+			struct omap_desc *d = c->desc;
+			ret = DMA_COMPLETE;
+			omap_dma_start_desc(c);
+			vchan_cookie_complete(&d->vd);
+		}
+	}
 
 	spin_unlock_irqrestore(&c->vc.lock, flags);
 

@@ -1180,7 +1189,10 @@ static struct dma_async_tx_descriptor *omap_dma_prep_dma_memcpy(
 	d->ccr = c->ccr;
 	d->ccr |= CCR_DST_AMODE_POSTINC | CCR_SRC_AMODE_POSTINC;
 
-	d->cicr = CICR_DROP_IE | CICR_FRAME_IE;
+	if (tx_flags & DMA_PREP_INTERRUPT)
+		d->cicr |= CICR_FRAME_IE;
+	else
+		d->polled = true;
 
 	d->csdp = data_type;
 

-- 
Peter

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

- Péter

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

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