[PATCH 06/30] rapidio/tsi721_dma: fix pending transaction queue handling

[Alexandre Bounine]

Fix pending DMA request queue handling to avoid broken ordering during
concurrent request submissions.

Signed-off-by: Alexandre Bounine <alexandre.bounine@xxxxxxx>
Cc: Matt Porter <mporter@xxxxxxxxxxxxxxxxxxx>
Cc: Aurelien Jacquiot <a-jacquiot@xxxxxx>
Cc: Andre van Herk <andre.van.herk@xxxxxxxxxxxxxxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
 drivers/rapidio/devices/tsi721.h     |    2 +-
 drivers/rapidio/devices/tsi721_dma.c |   60 +++++++++++++++++----------------
 2 files changed, 32 insertions(+), 30 deletions(-)

diff --git a/drivers/rapidio/devices/tsi721.h b/drivers/rapidio/devices/tsi721.h
index f81d011..d675a44 100644
--- a/drivers/rapidio/devices/tsi721.h
+++ b/drivers/rapidio/devices/tsi721.h
@@ -674,7 +674,7 @@ struct tsi721_bdma_chan {
 	struct dma_chan		dchan;
 	struct tsi721_tx_desc	*tx_desc;
 	spinlock_t		lock;
-	struct list_head	active_list;
+	struct tsi721_tx_desc	*active_tx;
 	struct list_head	queue;
 	struct list_head	free_list;
 	struct tasklet_struct	tasklet;
diff --git a/drivers/rapidio/devices/tsi721_dma.c b/drivers/rapidio/devices/tsi721_dma.c
index 4729594..500e1e0 100644
--- a/drivers/rapidio/devices/tsi721_dma.c
+++ b/drivers/rapidio/devices/tsi721_dma.c
@@ -63,14 +63,6 @@ struct tsi721_tx_desc *to_tsi721_desc(struct dma_async_tx_descriptor *txd)
 	return container_of(txd, struct tsi721_tx_desc, txd);
 }
 
-static inline
-struct tsi721_tx_desc *tsi721_dma_first_active(
-				struct tsi721_bdma_chan *bdma_chan)
-{
-	return list_first_entry(&bdma_chan->active_list,
-				struct tsi721_tx_desc, desc_node);
-}
-
 static int tsi721_bdma_ch_init(struct tsi721_bdma_chan *bdma_chan, int bd_num)
 {
 	struct tsi721_dma_desc *bd_ptr;
@@ -534,23 +526,30 @@ entry_done:
 	return err;
 }
 
-static void tsi721_advance_work(struct tsi721_bdma_chan *bdma_chan)
+static void tsi721_advance_work(struct tsi721_bdma_chan *bdma_chan,
+				struct tsi721_tx_desc *desc)
 {
-	struct tsi721_tx_desc *desc;
 	int err;
 
 	dev_dbg(bdma_chan->dchan.device->dev, "%s: Enter\n", __func__);
 
+	if (!tsi721_dma_is_idle(bdma_chan))
+		return;
+
 	/*
-	 * If there are any new transactions in the queue add them
-	 * into the processing list
-	 */
-	if (!list_empty(&bdma_chan->queue))
-		list_splice_init(&bdma_chan->queue, &bdma_chan->active_list);
+	 * If there is no data transfer in progress, fetch new descriptor from
+	 * the pending queue.
+	*/
+
+	if (desc == NULL && bdma_chan->active_tx == NULL &&
+					!list_empty(&bdma_chan->queue)) {
+		desc = list_first_entry(&bdma_chan->queue,
+					struct tsi721_tx_desc, desc_node);
+		list_del_init((&desc->desc_node));
+		bdma_chan->active_tx = desc;
+	}
 
-	/* Start new transaction (if available) */
-	if (!list_empty(&bdma_chan->active_list)) {
-		desc = tsi721_dma_first_active(bdma_chan);
+	if (desc) {
 		err = tsi721_submit_sg(desc);
 		if (!err)
 			tsi721_start_dma(bdma_chan);
@@ -581,6 +580,10 @@ static void tsi721_dma_tasklet(unsigned long data)
 		dev_err(bdma_chan->dchan.device->dev,
 			"%s: DMA ERROR - DMAC%d_STS = 0x%x\n",
 			__func__, bdma_chan->id, dmac_sts);
+
+		spin_lock(&bdma_chan->lock);
+		bdma_chan->active_tx = NULL;
+		spin_unlock(&bdma_chan->lock);
 	}
 
 	if (dmac_int & TSI721_DMAC_INT_STFULL) {
@@ -594,7 +597,7 @@ static void tsi721_dma_tasklet(unsigned long data)
 
 		tsi721_clr_stat(bdma_chan);
 		spin_lock(&bdma_chan->lock);
-		desc = tsi721_dma_first_active(bdma_chan);
+		desc = bdma_chan->active_tx;
 
 		if (desc->sg_len == 0) {
 			dma_async_tx_callback callback = NULL;
@@ -606,14 +609,15 @@ static void tsi721_dma_tasklet(unsigned long data)
 				callback = desc->txd.callback;
 				param = desc->txd.callback_param;
 			}
-			list_move(&desc->desc_node, &bdma_chan->free_list);
+			list_add(&desc->desc_node, &bdma_chan->free_list);
+			bdma_chan->active_tx = NULL;
 			spin_unlock(&bdma_chan->lock);
 			if (callback)
 				callback(param);
 			spin_lock(&bdma_chan->lock);
 		}
 
-		tsi721_advance_work(bdma_chan);
+		tsi721_advance_work(bdma_chan, bdma_chan->active_tx);
 		spin_unlock(&bdma_chan->lock);
 	}
 
@@ -720,9 +724,6 @@ static void tsi721_free_chan_resources(struct dma_chan *dchan)
 	if (bdma_chan->bd_base == NULL)
 		return;
 
-	BUG_ON(!list_empty(&bdma_chan->active_list));
-	BUG_ON(!list_empty(&bdma_chan->queue));
-
 	tsi721_bdma_interrupt_enable(bdma_chan, 0);
 	bdma_chan->active = false;
 	tsi721_sync_dma_irq(bdma_chan);
@@ -745,11 +746,11 @@ static void tsi721_issue_pending(struct dma_chan *dchan)
 
 	dev_dbg(dchan->device->dev, "%s: Enter\n", __func__);
 
+	spin_lock_bh(&bdma_chan->lock);
 	if (tsi721_dma_is_idle(bdma_chan) && bdma_chan->active) {
-		spin_lock_bh(&bdma_chan->lock);
-		tsi721_advance_work(bdma_chan);
-		spin_unlock_bh(&bdma_chan->lock);
+		tsi721_advance_work(bdma_chan, NULL);
 	}
+	spin_unlock_bh(&bdma_chan->lock);
 }
 
 static
@@ -839,7 +840,8 @@ static int tsi721_terminate_all(struct dma_chan *dchan)
 		} while ((dmac_int & TSI721_DMAC_INT_SUSP) == 0);
 	}
 
-	list_splice_init(&bdma_chan->active_list, &list);
+	if (bdma_chan->active_tx)
+		list_add(&bdma_chan->active_tx->desc_node, &list);
 	list_splice_init(&bdma_chan->queue, &list);
 
 	list_for_each_entry_safe(desc, _d, &list, desc_node)
@@ -875,7 +877,7 @@ int tsi721_register_dma(struct tsi721_device *priv)
 
 		spin_lock_init(&bdma_chan->lock);
 
-		INIT_LIST_HEAD(&bdma_chan->active_list);
+		bdma_chan->active_tx = NULL;
 		INIT_LIST_HEAD(&bdma_chan->queue);
 		INIT_LIST_HEAD(&bdma_chan->free_list);
 
-- 
1.7.8.4