net: macb: generalize tx buffer handling

Rename struct macb_tx_buff member skb to ptr and introduce
macb_tx_buff_type to identify the buffer type macb_tx_buff
represents.

Currently the buffer can only be MACB_TYPE_SKB, so the sk_buff
case is handled unconditionally in the tx path.
The remaining type handling will be handled by subsequent patches.

This is the last preparatory step for XDP xmit support.

Signed-off-by: Paolo Valerio <pvalerio@redhat.com>

Author: vlrpl

drivers/net/ethernet/cadence/macb.h

@@ -988,19 +988,28 @@ struct macb_dma_desc_ptp {
 /* Scaled PPM fraction */
 #define PPM_FRACTION	16
 
-/* struct macb_tx_buff - data about an skb which is being transmitted
- * @skb: skb currently being transmitted, only set for the last buffer
- *       of the frame
- * @mapping: DMA address of the skb's fragment buffer
+enum macb_tx_buff_type {
+	MACB_TYPE_SKB,
+	MACB_TYPE_XDP_TX,
+	MACB_TYPE_XDP_NDO,
+};
+
+/* struct macb_tx_buff - data about an skb or xdp frame which is being
+ * transmitted.
+ * @ptr: pointer to skb or xdp frame being transmitted, only set
+ *        for the last buffer for sk_buff
+ * @mapping: DMA address of the skb's fragment or xdp buffer
  * @size: size of the DMA mapped buffer
  * @mapped_as_page: true when buffer was mapped with skb_frag_dma_map(),
  *                  false when buffer was mapped with dma_map_single()
+ * @type: type of buffer (MACB_TYPE_SKB, MACB_TYPE_XDP_TX, MACB_TYPE_XDP_NDO)
  */
 struct macb_tx_buff {
-	struct sk_buff		*skb;
-	dma_addr_t		mapping;
-	size_t			size;
-	bool			mapped_as_page;
+	void				*ptr;
+	dma_addr_t			mapping;
+	size_t				size;
+	bool				mapped_as_page;
+	enum macb_tx_buff_type		type;
 };
 
 /* Hardware-collected statistics. Used when updating the network

drivers/net/ethernet/cadence/macb_main.c

@@ -1230,7 +1230,8 @@ static int macb_halt_tx(struct macb *bp)
 					bp, TSR);
 }
 
-static void macb_tx_unmap(struct macb *bp, struct macb_tx_buff *tx_buff, int budget)
+static void macb_tx_unmap(struct macb *bp, struct macb_tx_buff *tx_buff,
+			  int budget)
 {
 	if (tx_buff->mapping) {
 		if (tx_buff->mapped_as_page)
@@ -1242,9 +1243,9 @@ static void macb_tx_unmap(struct macb *bp, struct macb_tx_buff *tx_buff, int bud
 		tx_buff->mapping = 0;
 	}
 
-	if (tx_buff->skb) {
-		napi_consume_skb(tx_buff->skb, budget);
-		tx_buff->skb = NULL;
+	if (tx_buff->ptr) {
+		napi_consume_skb(tx_buff->ptr, budget);
+		tx_buff->ptr = NULL;
 	}
 }
 
@@ -1335,15 +1336,15 @@ static void macb_tx_error_task(struct work_struct *work)
 		desc = macb_tx_desc(queue, tail);
 		ctrl = desc->ctrl;
 		tx_buff = macb_tx_buff(queue, tail);
-		skb = tx_buff->skb;
+		skb = tx_buff->ptr;
 
 		if (ctrl & MACB_BIT(TX_USED)) {
 			/* skb is set for the last buffer of the frame */
 			while (!skb) {
 				macb_tx_unmap(bp, tx_buff, 0);
 				tail++;
 				tx_buff = macb_tx_buff(queue, tail);
-				skb = tx_buff->skb;
+				skb = tx_buff->ptr;
 			}
 
 			/* ctrl still refers to the first buffer descriptor
@@ -1440,20 +1441,22 @@ static bool ptp_one_step_sync(struct sk_buff *skb)
 static int macb_tx_complete(struct macb_queue *queue, int budget)
 {
 	struct macb *bp = queue->bp;
-	u16 queue_index = queue - bp->queues;
 	unsigned long flags;
 	unsigned int tail;
 	unsigned int head;
+	u16 queue_index;
 	int packets = 0;
 	u32 bytes = 0;
 
+	queue_index  = queue - bp->queues;
+
 	spin_lock_irqsave(&queue->tx_ptr_lock, flags);
 	head = queue->tx_head;
 	for (tail = queue->tx_tail; tail != head && packets < budget; tail++) {
-		struct macb_tx_buff	*tx_buff;
-		struct sk_buff		*skb;
-		struct macb_dma_desc	*desc;
-		u32			ctrl;
+		struct macb_tx_buff *tx_buff;
+		struct macb_dma_desc *desc;
+		struct sk_buff *skb;
+		u32 ctrl;
 
 		desc = macb_tx_desc(queue, tail);
 
@@ -1471,7 +1474,7 @@ static int macb_tx_complete(struct macb_queue *queue, int budget)
 		/* Process all buffers of the current transmitted frame */
 		for (;; tail++) {
 			tx_buff = macb_tx_buff(queue, tail);
-			skb = tx_buff->skb;
+			skb = tx_buff->ptr;
 
 			/* First, update TX stats if needed */
 			if (skb) {
@@ -2408,7 +2411,8 @@ static unsigned int macb_tx_map(struct macb *bp,
 			goto dma_error;
 
 		/* Save info to properly release resources */
-		tx_buff->skb = NULL;
+		tx_buff->ptr = NULL;
+		tx_buff->type = MACB_TYPE_SKB;
 		tx_buff->mapping = mapping;
 		tx_buff->size = size;
 		tx_buff->mapped_as_page = false;
@@ -2437,7 +2441,8 @@ static unsigned int macb_tx_map(struct macb *bp,
 				goto dma_error;
 
 			/* Save info to properly release resources */
-			tx_buff->skb = NULL;
+			tx_buff->ptr = NULL;
+			tx_buff->type = MACB_TYPE_SKB;
 			tx_buff->mapping = mapping;
 			tx_buff->size = size;
 			tx_buff->mapped_as_page = true;
@@ -2456,7 +2461,8 @@ static unsigned int macb_tx_map(struct macb *bp,
 	}
 
 	/* This is the last buffer of the frame: save socket buffer */
-	tx_buff->skb = skb;
+	tx_buff->ptr = skb;
+	tx_buff->type = MACB_TYPE_SKB;
 
 	/* Update TX ring: update buffer descriptors in reverse order
 	 * to avoid race condition
@@ -5377,8 +5383,9 @@ static netdev_tx_t at91ether_start_xmit(struct sk_buff *skb,
 		netif_stop_queue(dev);
 
 		/* Store packet information (to free when Tx completed) */
-		lp->rm9200_txq[desc].skb = skb;
+		lp->rm9200_txq[desc].ptr = skb;
 		lp->rm9200_txq[desc].size = skb->len;
+		lp->rm9200_txq[desc].type = MACB_TYPE_SKB;
 		lp->rm9200_txq[desc].mapping = dma_map_single(&lp->pdev->dev, skb->data,
 							      skb->len, DMA_TO_DEVICE);
 		if (dma_mapping_error(&lp->pdev->dev, lp->rm9200_txq[desc].mapping)) {
@@ -5470,9 +5477,9 @@ static irqreturn_t at91ether_interrupt(int irq, void *dev_id)
 			dev->stats.tx_errors++;
 
 		desc = 0;
-		if (lp->rm9200_txq[desc].skb) {
-			dev_consume_skb_irq(lp->rm9200_txq[desc].skb);
-			lp->rm9200_txq[desc].skb = NULL;
+		if (lp->rm9200_txq[desc].ptr) {
+			dev_consume_skb_irq(lp->rm9200_txq[desc].ptr);
+			lp->rm9200_txq[desc].ptr = NULL;
 			dma_unmap_single(&lp->pdev->dev, lp->rm9200_txq[desc].mapping,
 					 lp->rm9200_txq[desc].size, DMA_TO_DEVICE);
 			dev->stats.tx_packets++;