async_tx: trim dma_async_tx_descriptor in 'no channel switch' case

Saves 24 bytes per descriptor (64-bit) when the channel-switching
capabilities of async_tx are not required.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

crypto/async_tx/async_tx.c

@@ -81,18 +81,13 @@ async_tx_channel_switch(struct dma_async_tx_descriptor *depend_tx,
 	struct dma_device *device = chan->device;
 	struct dma_async_tx_descriptor *intr_tx = (void *) ~0;
 
-	#ifdef CONFIG_ASYNC_TX_DISABLE_CHANNEL_SWITCH
-	BUG();
-	#endif
-
 	/* first check to see if we can still append to depend_tx */
-	spin_lock_bh(&depend_tx->lock);
-	if (depend_tx->parent && depend_tx->chan == tx->chan) {
-		tx->parent = depend_tx;
-		depend_tx->next = tx;
+	txd_lock(depend_tx);
+	if (txd_parent(depend_tx) && depend_tx->chan == tx->chan) {
+		txd_chain(depend_tx, tx);
 		intr_tx = NULL;
 	}
-	spin_unlock_bh(&depend_tx->lock);
+	txd_unlock(depend_tx);
 
 	/* attached dependency, flush the parent channel */
 	if (!intr_tx) {
@@ -111,24 +106,22 @@ async_tx_channel_switch(struct dma_async_tx_descriptor *depend_tx,
 	if (intr_tx) {
 		intr_tx->callback = NULL;
 		intr_tx->callback_param = NULL;
-		tx->parent = intr_tx;
-		/* safe to set ->next outside the lock since we know we are
+		/* safe to chain outside the lock since we know we are
 		 * not submitted yet
 		 */
-		intr_tx->next = tx;
+		txd_chain(intr_tx, tx);
 
 		/* check if we need to append */
-		spin_lock_bh(&depend_tx->lock);
-		if (depend_tx->parent) {
-			intr_tx->parent = depend_tx;
-			depend_tx->next = intr_tx;
+		txd_lock(depend_tx);
+		if (txd_parent(depend_tx)) {
+			txd_chain(depend_tx, intr_tx);
 			async_tx_ack(intr_tx);
 			intr_tx = NULL;
 		}
-		spin_unlock_bh(&depend_tx->lock);
+		txd_unlock(depend_tx);
 
 		if (intr_tx) {
-			intr_tx->parent = NULL;
+			txd_clear_parent(intr_tx);
 			intr_tx->tx_submit(intr_tx);
 			async_tx_ack(intr_tx);
 		}
@@ -176,21 +169,20 @@ async_tx_submit(struct dma_chan *chan, struct dma_async_tx_descriptor *tx,
 		 * 2/ dependencies are 1:1 i.e. two transactions can
 		 * not depend on the same parent
 		 */
-		BUG_ON(async_tx_test_ack(depend_tx) || depend_tx->next ||
-		       tx->parent);
+		BUG_ON(async_tx_test_ack(depend_tx) || txd_next(depend_tx) ||
+		       txd_parent(tx));
 
 		/* the lock prevents async_tx_run_dependencies from missing
 		 * the setting of ->next when ->parent != NULL
 		 */
-		spin_lock_bh(&depend_tx->lock);
-		if (depend_tx->parent) {
+		txd_lock(depend_tx);
+		if (txd_parent(depend_tx)) {
 			/* we have a parent so we can not submit directly
 			 * if we are staying on the same channel: append
 			 * else: channel switch
 			 */
 			if (depend_tx->chan == chan) {
-				tx->parent = depend_tx;
-				depend_tx->next = tx;
+				txd_chain(depend_tx, tx);
 				s = ASYNC_TX_SUBMITTED;
 			} else
 				s = ASYNC_TX_CHANNEL_SWITCH;
@@ -203,7 +195,7 @@ async_tx_submit(struct dma_chan *chan, struct dma_async_tx_descriptor *tx,
 			else
 				s = ASYNC_TX_CHANNEL_SWITCH;
 		}
-		spin_unlock_bh(&depend_tx->lock);
+		txd_unlock(depend_tx);
 
 		switch (s) {
 		case ASYNC_TX_SUBMITTED:
@@ -212,12 +204,12 @@ async_tx_submit(struct dma_chan *chan, struct dma_async_tx_descriptor *tx,
 			async_tx_channel_switch(depend_tx, tx);
 			break;
 		case ASYNC_TX_DIRECT_SUBMIT:
-			tx->parent = NULL;
+			txd_clear_parent(tx);
 			tx->tx_submit(tx);
 			break;
 		}
 	} else {
-		tx->parent = NULL;
+		txd_clear_parent(tx);
 		tx->tx_submit(tx);
 	}
 

drivers/dma/dmaengine.c

@@ -978,7 +978,9 @@ void dma_async_tx_descriptor_init(struct dma_async_tx_descriptor *tx,
 	struct dma_chan *chan)
 {
 	tx->chan = chan;
+	#ifndef CONFIG_ASYNC_TX_DISABLE_CHANNEL_SWITCH
 	spin_lock_init(&tx->lock);
+	#endif
 }
 EXPORT_SYMBOL(dma_async_tx_descriptor_init);
 
@@ -1011,7 +1013,7 @@ EXPORT_SYMBOL_GPL(dma_wait_for_async_tx);
  */
 void dma_run_dependencies(struct dma_async_tx_descriptor *tx)
 {
-	struct dma_async_tx_descriptor *dep = tx->next;
+	struct dma_async_tx_descriptor *dep = txd_next(tx);
 	struct dma_async_tx_descriptor *dep_next;
 	struct dma_chan *chan;
 
@@ -1019,7 +1021,7 @@ void dma_run_dependencies(struct dma_async_tx_descriptor *tx)
 		return;
 
 	/* we'll submit tx->next now, so clear the link */
-	tx->next = NULL;
+	txd_clear_next(tx);
 	chan = dep->chan;
 
 	/* keep submitting up until a channel switch is detected
@@ -1027,14 +1029,14 @@ void dma_run_dependencies(struct dma_async_tx_descriptor *tx)
 	 * processing the interrupt from async_tx_channel_switch
 	 */
 	for (; dep; dep = dep_next) {
-		spin_lock_bh(&dep->lock);
-		dep->parent = NULL;
-		dep_next = dep->next;
+		txd_lock(dep);
+		txd_clear_parent(dep);
+		dep_next = txd_next(dep);
 		if (dep_next && dep_next->chan == chan)
-			dep->next = NULL; /* ->next will be submitted */
+			txd_clear_next(dep); /* ->next will be submitted */
 		else
 			dep_next = NULL; /* submit current dep and terminate */
-		spin_unlock_bh(&dep->lock);
+		txd_unlock(dep);
 
 		dep->tx_submit(dep);
 	}

include/linux/dmaengine.h

@@ -230,11 +230,71 @@ struct dma_async_tx_descriptor {
 	dma_cookie_t (*tx_submit)(struct dma_async_tx_descriptor *tx);
 	dma_async_tx_callback callback;
 	void *callback_param;
+#ifndef CONFIG_ASYNC_TX_DISABLE_CHANNEL_SWITCH
 	struct dma_async_tx_descriptor *next;
 	struct dma_async_tx_descriptor *parent;
 	spinlock_t lock;
+#endif
 };
 
+#ifdef CONFIG_ASYNC_TX_DISABLE_CHANNEL_SWITCH
+static inline void txd_lock(struct dma_async_tx_descriptor *txd)
+{
+}
+static inline void txd_unlock(struct dma_async_tx_descriptor *txd)
+{
+}
+static inline void txd_chain(struct dma_async_tx_descriptor *txd, struct dma_async_tx_descriptor *next)
+{
+	BUG();
+}
+static inline void txd_clear_parent(struct dma_async_tx_descriptor *txd)
+{
+}
+static inline void txd_clear_next(struct dma_async_tx_descriptor *txd)
+{
+}
+static inline struct dma_async_tx_descriptor *txd_next(struct dma_async_tx_descriptor *txd)
+{
+	return NULL;
+}
+static inline struct dma_async_tx_descriptor *txd_parent(struct dma_async_tx_descriptor *txd)
+{
+	return NULL;
+}
+
+#else
+static inline void txd_lock(struct dma_async_tx_descriptor *txd)
+{
+	spin_lock_bh(&txd->lock);
+}
+static inline void txd_unlock(struct dma_async_tx_descriptor *txd)
+{
+	spin_unlock_bh(&txd->lock);
+}
+static inline void txd_chain(struct dma_async_tx_descriptor *txd, struct dma_async_tx_descriptor *next)
+{
+	txd->next = next;
+	next->parent = txd;
+}
+static inline void txd_clear_parent(struct dma_async_tx_descriptor *txd)
+{
+	txd->parent = NULL;
+}
+static inline void txd_clear_next(struct dma_async_tx_descriptor *txd)
+{
+	txd->next = NULL;
+}
+static inline struct dma_async_tx_descriptor *txd_parent(struct dma_async_tx_descriptor *txd)
+{
+	return txd->parent;
+}
+static inline struct dma_async_tx_descriptor *txd_next(struct dma_async_tx_descriptor *txd)
+{
+	return txd->next;
+}
+#endif
+
 /**
  * struct dma_device - info on the entity supplying DMA services
  * @chancnt: how many DMA channels are supported