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Date:   Mon,  4 Feb 2019 22:58:29 +0100
From:   Christian Lamparter <chunkeey@...il.com>
To:     netdev@...r.kernel.org
Cc:     "David S . Miller" <davem@...emloft.net>
Subject: [PATCH v2] net: emac: remove IBM_EMAC_RX_SKB_HEADROOM

The EMAC driver had a custom IBM_EMAC_RX_SKB_HEADROOM
Kconfig option that reserved additional skb headroom for RX.
This patch removes the option and migrates the code
to use napi_alloc_skb() and netdev_alloc_skb_ip_align()
in its place.

Signed-off-by: Christian Lamparter <chunkeey@...il.com>
---
 drivers/net/ethernet/ibm/emac/Kconfig | 12 -----
 drivers/net/ethernet/ibm/emac/core.c  | 64 ++++++++++++++++++---------
 drivers/net/ethernet/ibm/emac/core.h  | 10 ++---
 3 files changed, 47 insertions(+), 39 deletions(-)

diff --git a/drivers/net/ethernet/ibm/emac/Kconfig b/drivers/net/ethernet/ibm/emac/Kconfig
index 90d49191beb3..eacf7e141fdc 100644
--- a/drivers/net/ethernet/ibm/emac/Kconfig
+++ b/drivers/net/ethernet/ibm/emac/Kconfig
@@ -28,18 +28,6 @@ config IBM_EMAC_RX_COPY_THRESHOLD
 	depends on IBM_EMAC
 	default "256"
 
-config IBM_EMAC_RX_SKB_HEADROOM
-	int "Additional RX skb headroom (bytes)"
-	depends on IBM_EMAC
-	default "0"
-	help
-	  Additional receive skb headroom. Note, that driver
-	  will always reserve at least 2 bytes to make IP header
-	  aligned, so usually there is no need to add any additional
-	  headroom.
-
-	  If unsure, set to 0.
-
 config IBM_EMAC_DEBUG
 	bool "Debugging"
 	depends on IBM_EMAC
diff --git a/drivers/net/ethernet/ibm/emac/core.c b/drivers/net/ethernet/ibm/emac/core.c
index 209255495bc9..5fc5fa37d305 100644
--- a/drivers/net/ethernet/ibm/emac/core.c
+++ b/drivers/net/ethernet/ibm/emac/core.c
@@ -1071,7 +1071,9 @@ static int emac_resize_rx_ring(struct emac_instance *dev, int new_mtu)
 
 	/* Second pass, allocate new skbs */
 	for (i = 0; i < NUM_RX_BUFF; ++i) {
-		struct sk_buff *skb = alloc_skb(rx_skb_size, GFP_ATOMIC);
+		struct sk_buff *skb;
+
+		skb = netdev_alloc_skb_ip_align(dev->ndev, rx_skb_size);
 		if (!skb) {
 			ret = -ENOMEM;
 			goto oom;
@@ -1080,10 +1082,10 @@ static int emac_resize_rx_ring(struct emac_instance *dev, int new_mtu)
 		BUG_ON(!dev->rx_skb[i]);
 		dev_kfree_skb(dev->rx_skb[i]);
 
-		skb_reserve(skb, EMAC_RX_SKB_HEADROOM + 2);
 		dev->rx_desc[i].data_ptr =
-		    dma_map_single(&dev->ofdev->dev, skb->data - 2, rx_sync_size,
-				   DMA_FROM_DEVICE) + 2;
+		    dma_map_single(&dev->ofdev->dev, skb->data - NET_IP_ALIGN,
+				   rx_sync_size, DMA_FROM_DEVICE)
+				   + NET_IP_ALIGN;
 		dev->rx_skb[i] = skb;
 	}
  skip:
@@ -1174,20 +1176,18 @@ static void emac_clean_rx_ring(struct emac_instance *dev)
 	}
 }
 
-static inline int emac_alloc_rx_skb(struct emac_instance *dev, int slot,
-				    gfp_t flags)
+static inline int
+__emac_prepare_rx_skb(struct sk_buff *skb, struct emac_instance *dev, int slot)
 {
-	struct sk_buff *skb = alloc_skb(dev->rx_skb_size, flags);
 	if (unlikely(!skb))
 		return -ENOMEM;
 
 	dev->rx_skb[slot] = skb;
 	dev->rx_desc[slot].data_len = 0;
 
-	skb_reserve(skb, EMAC_RX_SKB_HEADROOM + 2);
 	dev->rx_desc[slot].data_ptr =
-	    dma_map_single(&dev->ofdev->dev, skb->data - 2, dev->rx_sync_size,
-			   DMA_FROM_DEVICE) + 2;
+	    dma_map_single(&dev->ofdev->dev, skb->data - NET_IP_ALIGN,
+			   dev->rx_sync_size, DMA_FROM_DEVICE) + NET_IP_ALIGN;
 	wmb();
 	dev->rx_desc[slot].ctrl = MAL_RX_CTRL_EMPTY |
 	    (slot == (NUM_RX_BUFF - 1) ? MAL_RX_CTRL_WRAP : 0);
@@ -1195,6 +1195,27 @@ static inline int emac_alloc_rx_skb(struct emac_instance *dev, int slot,
 	return 0;
 }
 
+static inline int
+emac_alloc_rx_skb(struct emac_instance *dev, int slot)
+{
+	struct sk_buff *skb;
+
+	skb = __netdev_alloc_skb_ip_align(dev->ndev, dev->rx_skb_size,
+					  GFP_KERNEL);
+
+	return __emac_prepare_rx_skb(skb, dev, slot);
+}
+
+static inline int
+emac_alloc_rx_skb_napi(struct emac_instance *dev, int slot)
+{
+	struct sk_buff *skb;
+
+	skb = napi_alloc_skb(&dev->mal->napi, dev->rx_skb_size);
+
+	return __emac_prepare_rx_skb(skb, dev, slot);
+}
+
 static void emac_print_link_status(struct emac_instance *dev)
 {
 	if (netif_carrier_ok(dev->ndev))
@@ -1225,7 +1246,7 @@ static int emac_open(struct net_device *ndev)
 
 	/* Allocate RX ring */
 	for (i = 0; i < NUM_RX_BUFF; ++i)
-		if (emac_alloc_rx_skb(dev, i, GFP_KERNEL)) {
+		if (emac_alloc_rx_skb(dev, i)) {
 			printk(KERN_ERR "%s: failed to allocate RX ring\n",
 			       ndev->name);
 			goto oom;
@@ -1660,8 +1681,9 @@ static inline void emac_recycle_rx_skb(struct emac_instance *dev, int slot,
 	DBG2(dev, "recycle %d %d" NL, slot, len);
 
 	if (len)
-		dma_map_single(&dev->ofdev->dev, skb->data - 2,
-			       EMAC_DMA_ALIGN(len + 2), DMA_FROM_DEVICE);
+		dma_map_single(&dev->ofdev->dev, skb->data - NET_IP_ALIGN,
+			       SKB_DATA_ALIGN(len + NET_IP_ALIGN),
+			       DMA_FROM_DEVICE);
 
 	dev->rx_desc[slot].data_len = 0;
 	wmb();
@@ -1713,7 +1735,7 @@ static inline int emac_rx_sg_append(struct emac_instance *dev, int slot)
 		int len = dev->rx_desc[slot].data_len;
 		int tot_len = dev->rx_sg_skb->len + len;
 
-		if (unlikely(tot_len + 2 > dev->rx_skb_size)) {
+		if (unlikely(tot_len + NET_IP_ALIGN > dev->rx_skb_size)) {
 			++dev->estats.rx_dropped_mtu;
 			dev_kfree_skb(dev->rx_sg_skb);
 			dev->rx_sg_skb = NULL;
@@ -1769,16 +1791,18 @@ static int emac_poll_rx(void *param, int budget)
 		}
 
 		if (len && len < EMAC_RX_COPY_THRESH) {
-			struct sk_buff *copy_skb =
-			    alloc_skb(len + EMAC_RX_SKB_HEADROOM + 2, GFP_ATOMIC);
+			struct sk_buff *copy_skb;
+
+			copy_skb = napi_alloc_skb(&dev->mal->napi, len);
 			if (unlikely(!copy_skb))
 				goto oom;
 
-			skb_reserve(copy_skb, EMAC_RX_SKB_HEADROOM + 2);
-			memcpy(copy_skb->data - 2, skb->data - 2, len + 2);
+			memcpy(copy_skb->data - NET_IP_ALIGN,
+			       skb->data - NET_IP_ALIGN,
+			       len + NET_IP_ALIGN);
 			emac_recycle_rx_skb(dev, slot, len);
 			skb = copy_skb;
-		} else if (unlikely(emac_alloc_rx_skb(dev, slot, GFP_ATOMIC)))
+		} else if (unlikely(emac_alloc_rx_skb_napi(dev, slot)))
 			goto oom;
 
 		skb_put(skb, len);
@@ -1799,7 +1823,7 @@ static int emac_poll_rx(void *param, int budget)
 	sg:
 		if (ctrl & MAL_RX_CTRL_FIRST) {
 			BUG_ON(dev->rx_sg_skb);
-			if (unlikely(emac_alloc_rx_skb(dev, slot, GFP_ATOMIC))) {
+			if (unlikely(emac_alloc_rx_skb_napi(dev, slot))) {
 				DBG(dev, "rx OOM %d" NL, slot);
 				++dev->estats.rx_dropped_oom;
 				emac_recycle_rx_skb(dev, slot, 0);
diff --git a/drivers/net/ethernet/ibm/emac/core.h b/drivers/net/ethernet/ibm/emac/core.h
index 84caa4a3fc52..187689cd8212 100644
--- a/drivers/net/ethernet/ibm/emac/core.h
+++ b/drivers/net/ethernet/ibm/emac/core.h
@@ -68,22 +68,18 @@ static inline int emac_rx_size(int mtu)
 		return mal_rx_size(ETH_DATA_LEN + EMAC_MTU_OVERHEAD);
 }
 
-#define EMAC_DMA_ALIGN(x)		ALIGN((x), dma_get_cache_alignment())
-
-#define EMAC_RX_SKB_HEADROOM		\
-	EMAC_DMA_ALIGN(CONFIG_IBM_EMAC_RX_SKB_HEADROOM)
-
 /* Size of RX skb for the given MTU */
 static inline int emac_rx_skb_size(int mtu)
 {
 	int size = max(mtu + EMAC_MTU_OVERHEAD, emac_rx_size(mtu));
-	return EMAC_DMA_ALIGN(size + 2) + EMAC_RX_SKB_HEADROOM;
+
+	return SKB_DATA_ALIGN(size + NET_IP_ALIGN) + NET_SKB_PAD;
 }
 
 /* RX DMA sync size */
 static inline int emac_rx_sync_size(int mtu)
 {
-	return EMAC_DMA_ALIGN(emac_rx_size(mtu) + 2);
+	return SKB_DATA_ALIGN(emac_rx_size(mtu) + NET_IP_ALIGN);
 }
 
 /* Driver statistcs is split into two parts to make it more cache friendly:
-- 
2.20.1

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