[PATCH net-next v2 13/15] net: stmmac: add helper to set transmit tail pointer

["Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>]

Setting the queue transmit tail pointer follows a common pattern:
calculate the DMA address, and then call stmmac_set_tx_tail_ptr().
The only difference between all the call sites is the index used.

Factor this out into a static function.

We need to update dwmac4_display_ring() to cope the passed head
pointer always pointing at the struct dma_desc by using
dma_desc_to_edesc() to convert it to struct dma_edesc. This is the
only stmmac_display_ring() implementation that this affects.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
 .../ethernet/stmicro/stmmac/dwmac4_descs.c    |  2 +-
 .../net/ethernet/stmicro/stmmac/stmmac_main.c | 30 ++++++++++---------
 2 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
index 1bbf02504dad..d5c003f3fbbc 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c
@@ -427,7 +427,7 @@ static void dwmac4_display_ring(void *head, unsigned int size, bool rx,
 			extp++;
 		}
 	} else if (desc_size == sizeof(struct dma_edesc)) {
-		struct dma_edesc *ep = (struct dma_edesc *)head;
+		struct dma_edesc *ep = dma_desc_to_edesc(head);
 
 		for (i = 0; i < size; i++) {
 			dma_addr = dma_rx_phy + i * sizeof(*ep);
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index da1726b887f3..4521469c5e1d 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -385,6 +385,18 @@ static struct dma_desc *stmmac_get_tx_desc(struct stmmac_priv *priv,
 		return &tx_q->dma_tx[index];
 }
 
+static void stmmac_set_queue_tx_tail_ptr(struct stmmac_priv *priv,
+					 struct stmmac_tx_queue *tx_q,
+					 unsigned int chan, unsigned int index)
+{
+	int desc_size;
+
+	desc_size = stmmac_get_tx_desc_size(priv, tx_q);
+
+	tx_q->tx_tail_addr = tx_q->dma_tx_phy + index * desc_size;
+	stmmac_set_tx_tail_ptr(priv, priv->ioaddr, tx_q->tx_tail_addr, chan);
+}
+
 static size_t stmmac_get_rx_desc_size(struct stmmac_priv *priv)
 {
 	if (priv->extend_desc)
@@ -3311,9 +3323,7 @@ static int stmmac_init_dma_engine(struct stmmac_priv *priv)
 		stmmac_init_tx_chan(priv, priv->ioaddr, priv->plat->dma_cfg,
 				    tx_q->dma_tx_phy, chan);
 
-		tx_q->tx_tail_addr = tx_q->dma_tx_phy;
-		stmmac_set_tx_tail_ptr(priv, priv->ioaddr,
-				       tx_q->tx_tail_addr, chan);
+		stmmac_set_queue_tx_tail_ptr(priv, tx_q, chan, 0);
 	}
 
 	return ret;
@@ -4326,9 +4336,6 @@ static void stmmac_tso_allocator(struct stmmac_priv *priv, dma_addr_t des,
 static void stmmac_flush_tx_descriptors(struct stmmac_priv *priv, int queue)
 {
 	struct stmmac_tx_queue *tx_q = &priv->dma_conf.tx_queue[queue];
-	int desc_size;
-
-	desc_size = stmmac_get_tx_desc_size(priv, tx_q);
 
 	/* The own bit must be the latest setting done when prepare the
 	 * descriptor and then barrier is needed to make sure that
@@ -4336,8 +4343,7 @@ static void stmmac_flush_tx_descriptors(struct stmmac_priv *priv, int queue)
 	 */
 	wmb();
 
-	tx_q->tx_tail_addr = tx_q->dma_tx_phy + (tx_q->cur_tx * desc_size);
-	stmmac_set_tx_tail_ptr(priv, priv->ioaddr, tx_q->tx_tail_addr, queue);
+	stmmac_set_queue_tx_tail_ptr(priv, tx_q, queue, tx_q->cur_tx);
 }
 
 /**
@@ -6967,9 +6973,7 @@ void stmmac_enable_tx_queue(struct stmmac_priv *priv, u32 queue)
 	if (tx_q->tbs & STMMAC_TBS_AVAIL)
 		stmmac_enable_tbs(priv, priv->ioaddr, 1, tx_q->queue_index);
 
-	tx_q->tx_tail_addr = tx_q->dma_tx_phy;
-	stmmac_set_tx_tail_ptr(priv, priv->ioaddr,
-			       tx_q->tx_tail_addr, tx_q->queue_index);
+	stmmac_set_queue_tx_tail_ptr(priv, tx_q, tx_q->queue_index, 0);
 
 	stmmac_start_tx_dma(priv, queue);
 
@@ -7070,9 +7074,7 @@ int stmmac_xdp_open(struct net_device *dev)
 		stmmac_init_tx_chan(priv, priv->ioaddr, priv->plat->dma_cfg,
 				    tx_q->dma_tx_phy, chan);
 
-		tx_q->tx_tail_addr = tx_q->dma_tx_phy;
-		stmmac_set_tx_tail_ptr(priv, priv->ioaddr,
-				       tx_q->tx_tail_addr, chan);
+		stmmac_set_queue_tx_tail_ptr(priv, tx_q, chan, 0);
 
 		hrtimer_setup(&tx_q->txtimer, stmmac_tx_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	}
-- 
2.47.3