netdev - [PATCH (net-next.git) 16/18] stmmac: do not perform zero-copy for rx frames

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Date:	Wed, 9 Dec 2015 09:37:52 +0100
From:	Giuseppe Cavallaro <peppe.cavallaro@...com>
To:	<netdev@...r.kernel.org>
CC:	<alexandre.torgue@...com>,
	Giuseppe Cavallaro <peppe.cavallaro@...com>
Subject: [PATCH (net-next.git) 16/18] stmmac: do not perform zero-copy for rx frames

This patch is to allow this driver to copy tiny frames during the reception
process. This is giving more stability while stressing the driver on STi
embedded systems.

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@...com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c |   67 ++++++++++++++++-----
 1 files changed, 52 insertions(+), 15 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 6b83213..d68775a 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -98,6 +98,10 @@ static int buf_sz = DEFAULT_BUFSIZE;
 module_param(buf_sz, int, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(buf_sz, "DMA buffer size");
 
+static int minrx = 256;
+module_param(minrx, int, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(minrx, "Copy only tiny-frames");
+
 static const u32 default_msg_level = (NETIF_MSG_DRV | NETIF_MSG_PROBE |
 				      NETIF_MSG_LINK | NETIF_MSG_IFUP |
 				      NETIF_MSG_IFDOWN | NETIF_MSG_TIMER);
@@ -147,6 +151,8 @@ static void stmmac_verify_args(void)
 		pause = PAUSE_TIME;
 	if (eee_timer < 0)
 		eee_timer = STMMAC_DEFAULT_LPI_TIMER;
+	if (minrx < 0)
+		minrx = ETH_FRAME_LEN;
 }
 
 /**
@@ -2198,8 +2204,7 @@ static inline void stmmac_rx_refill(struct stmmac_priv *priv)
 			struct sk_buff *skb;
 
 			skb = netdev_alloc_skb_ip_align(priv->dev, bfsize);
-
-			if (unlikely(skb == NULL))
+			if (unlikely(!skb))
 				break;
 
 			priv->rx_skbuff[entry] = skb;
@@ -2322,23 +2327,52 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit)
 					pr_debug("\tframe size %d, COE: %d\n",
 						 frame_len, status);
 			}
-			skb = priv->rx_skbuff[entry];
-			if (unlikely(!skb)) {
-				pr_err("%s: Inconsistent Rx descriptor chain\n",
-				       priv->dev->name);
-				priv->dev->stats.rx_dropped++;
-				break;
+
+			if (unlikely(frame_len < minrx)) {
+				skb = netdev_alloc_skb_ip_align(priv->dev,
+								frame_len);
+				if (unlikely(!skb)) {
+					if (net_ratelimit())
+						dev_warn(priv->device,
+							 "packet dropped\n");
+					priv->dev->stats.rx_dropped++;
+					break;
+				}
+
+				dma_sync_single_for_cpu(priv->device,
+							priv->rx_skbuff_dma
+							[entry], frame_len,
+							DMA_FROM_DEVICE);
+				skb_copy_to_linear_data(skb,
+							priv->
+							rx_skbuff[entry]->data,
+							frame_len);
+
+				skb_put(skb, frame_len);
+				dma_sync_single_for_device(priv->device,
+							   priv->rx_skbuff_dma
+							   [entry], frame_len,
+							   DMA_FROM_DEVICE);
+			} else {
+				skb = priv->rx_skbuff[entry];
+				if (unlikely(!skb)) {
+					pr_err("%s: Inconsistent Rx chain\n",
+					       priv->dev->name);
+					priv->dev->stats.rx_dropped++;
+					break;
+				}
+				prefetch(skb->data - NET_IP_ALIGN);
+				priv->rx_skbuff[entry] = NULL;
+
+				skb_put(skb, frame_len);
+				dma_unmap_single(priv->device,
+						 priv->rx_skbuff_dma[entry],
+						 priv->dma_buf_sz,
+						 DMA_FROM_DEVICE);
 			}
-			prefetch(skb->data - NET_IP_ALIGN);
-			priv->rx_skbuff[entry] = NULL;
 
 			stmmac_get_rx_hwtstamp(priv, entry, skb);
 
-			skb_put(skb, frame_len);
-			dma_unmap_single(priv->device,
-					 priv->rx_skbuff_dma[entry],
-					 priv->dma_buf_sz, DMA_FROM_DEVICE);
-
 			if (netif_msg_pktdata(priv)) {
 				pr_debug("frame received (%dbytes)", frame_len);
 				print_pkt(skb->data, frame_len);
@@ -3235,6 +3269,9 @@ static int __init stmmac_cmdline_opt(char *str)
 		} else if (!strncmp(opt, "chain_mode:", 11)) {
 			if (kstrtoint(opt + 11, 0, &chain_mode))
 				goto err;
+		} else if (!strncmp(opt, "minrx:", 6)) {
+			if (kstrtoint(opt + 6, 0, &minrx))
+				goto err;
 		}
 	}
 	return 0;
-- 
1.7.4.4

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