linux-kernel - [PATCH v3 2/4] mt76: add unlikely() for dma_mapping

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Date:   Mon, 1 Apr 2019 15:16:42 +0800
From:   Ryder Lee <ryder.lee@...iatek.com>
To:     Lorenzo Bianconi <lorenzo.bianconi@...hat.com>,
        Felix Fietkau <nbd@....name>
CC:     Roy Luo <royluo@...gle.com>, Sean Wang <sean.wang@...iatek.com>,
        Nelson Chang <nelson.chang@...iatek.com>,
        YF Luo <yf.luo@...iatek.com>, Kai Lin <kai.lin@...iatek.com>,
        Rorscha Yang <rorscha.yang@...iatek.com>,
        Kyle Lee <kyle.lee@...iatek.com>,
        Miller Shen <miller.shen@...iatek.com>,
        Haipin Liang <haipin.liang@...iatek.com>,
        KL Huang <kl.huang@...iatek.com>,
        YH chen <yh.chen@...iatek.com>,
        <linux-wireless@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, Ryder Lee <ryder.lee@...iatek.com>
Subject: [PATCH v3 2/4] mt76: add unlikely() for dma_mapping_error() check

In the tx/rx fastpath, the funciton dma_map_single() rarely fails.
This adds unlikely() optimization to this error check conditional.

Signed-off-by: Ryder Lee <ryder.lee@...iatek.com>
---
 drivers/net/wireless/mediatek/mt76/dma.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/dma.c b/drivers/net/wireless/mediatek/mt76/dma.c
index 8a4b935..6f3ef09 100644
--- a/drivers/net/wireless/mediatek/mt76/dma.c
+++ b/drivers/net/wireless/mediatek/mt76/dma.c
@@ -272,7 +272,7 @@
 
 	addr = dma_map_single(dev->dev, skb->data, skb->len,
 			      DMA_TO_DEVICE);
-	if (dma_mapping_error(dev->dev, addr))
+	if (unlikely(dma_mapping_error(dev->dev, addr)))
 		return -ENOMEM;
 
 	buf.addr = addr;
@@ -315,7 +315,7 @@
 
 	len = skb_headlen(skb);
 	addr = dma_map_single(dev->dev, skb->data, len, DMA_TO_DEVICE);
-	if (dma_mapping_error(dev->dev, addr))
+	if (unlikely(dma_mapping_error(dev->dev, addr)))
 		goto free;
 
 	tx_info.buf[n].addr = t->dma_addr;
@@ -329,7 +329,7 @@
 
 		addr = dma_map_single(dev->dev, iter->data, iter->len,
 				      DMA_TO_DEVICE);
-		if (dma_mapping_error(dev->dev, addr))
+		if (unlikely(dma_mapping_error(dev->dev, addr)))
 			goto unmap;
 
 		tx_info.buf[n].addr = addr;
@@ -386,7 +386,7 @@
 			break;
 
 		addr = dma_map_single(dev->dev, buf, len, DMA_FROM_DEVICE);
-		if (dma_mapping_error(dev->dev, addr)) {
+		if (unlikely(dma_mapping_error(dev->dev, addr))) {
 			skb_free_frag(buf);
 			break;
 		}
-- 
1.9.1