dmaengine: mdc: Correct terminate_all handling

Use of the CANCEL bit in mdc_terminate_all creates an
additional 'command done' to appear in the registers (in
addition to an interrupt).

In addition, there is a potential race between
mdc_terminate_all and the irq handler if a transfer
completes at the same time as the terminate all (presently
this results in an inappropriate warning).

To handle these issues, any outstanding 'command done'
events are cleared during mdc_terminate_all and the irq
handler takes no action when there are no new 'command done'
events.

Signed-off-by: Damien.Horsley <Damien.Horsley@imgtec.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/img-mdc-dma.c

@@ -651,6 +651,48 @@ static enum dma_status mdc_tx_status(struct dma_chan *chan,
 	return ret;
 }
 
+static unsigned int mdc_get_new_events(struct mdc_chan *mchan)
+{
+	u32 val, processed, done1, done2;
+	unsigned int ret;
+
+	val = mdc_chan_readl(mchan, MDC_CMDS_PROCESSED);
+	processed = (val >> MDC_CMDS_PROCESSED_CMDS_PROCESSED_SHIFT) &
+				MDC_CMDS_PROCESSED_CMDS_PROCESSED_MASK;
+	/*
+	 * CMDS_DONE may have incremented between reading CMDS_PROCESSED
+	 * and clearing INT_ACTIVE.  Re-read CMDS_PROCESSED to ensure we
+	 * didn't miss a command completion.
+	 */
+	do {
+		val = mdc_chan_readl(mchan, MDC_CMDS_PROCESSED);
+
+		done1 = (val >> MDC_CMDS_PROCESSED_CMDS_DONE_SHIFT) &
+			MDC_CMDS_PROCESSED_CMDS_DONE_MASK;
+
+		val &= ~((MDC_CMDS_PROCESSED_CMDS_PROCESSED_MASK <<
+			  MDC_CMDS_PROCESSED_CMDS_PROCESSED_SHIFT) |
+			 MDC_CMDS_PROCESSED_INT_ACTIVE);
+
+		val |= done1 << MDC_CMDS_PROCESSED_CMDS_PROCESSED_SHIFT;
+
+		mdc_chan_writel(mchan, val, MDC_CMDS_PROCESSED);
+
+		val = mdc_chan_readl(mchan, MDC_CMDS_PROCESSED);
+
+		done2 = (val >> MDC_CMDS_PROCESSED_CMDS_DONE_SHIFT) &
+			MDC_CMDS_PROCESSED_CMDS_DONE_MASK;
+	} while (done1 != done2);
+
+	if (done1 >= processed)
+		ret = done1 - processed;
+	else
+		ret = ((MDC_CMDS_PROCESSED_CMDS_PROCESSED_MASK + 1) -
+			processed) + done1;
+
+	return ret;
+}
+
 static int mdc_terminate_all(struct dma_chan *chan)
 {
 	struct mdc_chan *mchan = to_mdc_chan(chan);
@@ -667,6 +709,8 @@ static int mdc_terminate_all(struct dma_chan *chan)
 	mchan->desc = NULL;
 	vchan_get_all_descriptors(&mchan->vc, &head);
 
+	mdc_get_new_events(mchan);
+
 	spin_unlock_irqrestore(&mchan->vc.lock, flags);
 
 	if (mdesc)
@@ -703,35 +747,17 @@ static irqreturn_t mdc_chan_irq(int irq, void *dev_id)
 {
 	struct mdc_chan *mchan = (struct mdc_chan *)dev_id;
 	struct mdc_tx_desc *mdesc;
-	u32 val, processed, done1, done2;
-	unsigned int i;
+	unsigned int i, new_events;
 
 	spin_lock(&mchan->vc.lock);
 
-	val = mdc_chan_readl(mchan, MDC_CMDS_PROCESSED);
-	processed = (val >> MDC_CMDS_PROCESSED_CMDS_PROCESSED_SHIFT) &
-		MDC_CMDS_PROCESSED_CMDS_PROCESSED_MASK;
-	/*
-	 * CMDS_DONE may have incremented between reading CMDS_PROCESSED
-	 * and clearing INT_ACTIVE.  Re-read CMDS_PROCESSED to ensure we
-	 * didn't miss a command completion.
-	 */
-	do {
-		val = mdc_chan_readl(mchan, MDC_CMDS_PROCESSED);
-		done1 = (val >> MDC_CMDS_PROCESSED_CMDS_DONE_SHIFT) &
-			MDC_CMDS_PROCESSED_CMDS_DONE_MASK;
-		val &= ~((MDC_CMDS_PROCESSED_CMDS_PROCESSED_MASK <<
-			  MDC_CMDS_PROCESSED_CMDS_PROCESSED_SHIFT) |
-			 MDC_CMDS_PROCESSED_INT_ACTIVE);
-		val |= done1 << MDC_CMDS_PROCESSED_CMDS_PROCESSED_SHIFT;
-		mdc_chan_writel(mchan, val, MDC_CMDS_PROCESSED);
-		val = mdc_chan_readl(mchan, MDC_CMDS_PROCESSED);
-		done2 = (val >> MDC_CMDS_PROCESSED_CMDS_DONE_SHIFT) &
-			MDC_CMDS_PROCESSED_CMDS_DONE_MASK;
-	} while (done1 != done2);
-
 	dev_dbg(mdma2dev(mchan->mdma), "IRQ on channel %d\n", mchan->chan_nr);
 
+	new_events = mdc_get_new_events(mchan);
+
+	if (!new_events)
+		goto out;
+
 	mdesc = mchan->desc;
 	if (!mdesc) {
 		dev_warn(mdma2dev(mchan->mdma),
@@ -740,8 +766,7 @@ static irqreturn_t mdc_chan_irq(int irq, void *dev_id)
 		goto out;
 	}
 
-	for (i = processed; i != done1;
-	     i = (i + 1) % (MDC_CMDS_PROCESSED_CMDS_PROCESSED_MASK + 1)) {
+	for (i = 0; i < new_events; i++) {
 		/*
 		 * The first interrupt in a transfer indicates that the
 		 * command list has been loaded, not that a command has