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Date:	Mon,  7 Dec 2015 10:30:33 +0530
From:	Sunil Goutham <sunil.kovvuri@...il.com>
To:	netdev@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	p.fedin@...sung.com, Sunil.Goutham@...iumnetworks.com,
	Sunil Goutham <sgoutham@...ium.com>
Subject: [PATCH 2/2] net, thunderx: Remove unnecessary rcv buffer start address management

From: Sunil Goutham <sgoutham@...ium.com>

Since we have moved on to using allocated pages to carve receive
buffers instead of netdev_alloc_skb() there is no need to store
any pointers for later retrieval. Earlier we had to store
skb and skb->data pointers which later are used to handover
received packet to network stack.

This will avoid an unnecessary cache miss as well.

Signed-off-by: Sunil Goutham <sgoutham@...ium.com>
---
 drivers/net/ethernet/cavium/thunder/nicvf_queues.c |   49 ++++----------------
 drivers/net/ethernet/cavium/thunder/nicvf_queues.h |   10 +---
 2 files changed, 11 insertions(+), 48 deletions(-)

diff --git a/drivers/net/ethernet/cavium/thunder/nicvf_queues.c b/drivers/net/ethernet/cavium/thunder/nicvf_queues.c
index 99a29d0..1fbd908 100644
--- a/drivers/net/ethernet/cavium/thunder/nicvf_queues.c
+++ b/drivers/net/ethernet/cavium/thunder/nicvf_queues.c
@@ -18,14 +18,6 @@
 #include "q_struct.h"
 #include "nicvf_queues.h"
 
-struct rbuf_info {
-	struct page *page;
-	void	*data;
-	u64	offset;
-};
-
-#define GET_RBUF_INFO(x) ((struct rbuf_info *)(x - NICVF_RCV_BUF_ALIGN_BYTES))
-
 /* Poll a register for a specific value */
 static int nicvf_poll_reg(struct nicvf *nic, int qidx,
 			  u64 reg, int bit_pos, int bits, int val)
@@ -86,8 +78,6 @@ static void nicvf_free_q_desc_mem(struct nicvf *nic, struct q_desc_mem *dmem)
 static inline int nicvf_alloc_rcv_buffer(struct nicvf *nic, gfp_t gfp,
 					 u32 buf_len, u64 **rbuf)
 {
-	u64 data;
-	struct rbuf_info *rinfo;
 	int order = get_order(buf_len);
 
 	/* Check if request can be accomodated in previous allocated page */
@@ -113,46 +103,28 @@ static inline int nicvf_alloc_rcv_buffer(struct nicvf *nic, gfp_t gfp,
 		nic->rb_page_offset = 0;
 	}
 
-	data = (u64)page_address(nic->rb_page) + nic->rb_page_offset;
-
-	/* Align buffer addr to cache line i.e 128 bytes */
-	rinfo = (struct rbuf_info *)(data + NICVF_RCV_BUF_ALIGN_LEN(data));
-	/* Save page address for reference updation */
-	rinfo->page = nic->rb_page;
-	/* Store start address for later retrieval */
-	rinfo->data = (void *)data;
-	/* Store alignment offset */
-	rinfo->offset = NICVF_RCV_BUF_ALIGN_LEN(data);
+	*rbuf = (u64 *)((u64)page_address(nic->rb_page) + nic->rb_page_offset);
 
-	data += rinfo->offset;
-
-	/* Give next aligned address to hw for DMA */
-	*rbuf = (u64 *)(data + NICVF_RCV_BUF_ALIGN_BYTES);
 	return 0;
 }
 
-/* Retrieve actual buffer start address and build skb for received packet */
+/* Build skb around receive buffer */
 static struct sk_buff *nicvf_rb_ptr_to_skb(struct nicvf *nic,
 					   u64 rb_ptr, int len)
 {
+	void *data;
 	struct sk_buff *skb;
-	struct rbuf_info *rinfo;
 
-	rb_ptr = (u64)phys_to_virt(rb_ptr);
-	/* Get buffer start address and alignment offset */
-	rinfo = GET_RBUF_INFO(rb_ptr);
+	data = phys_to_virt(rb_ptr);
 
 	/* Now build an skb to give to stack */
-	skb = build_skb(rinfo->data, RCV_FRAG_LEN);
+	skb = build_skb(data, RCV_FRAG_LEN);
 	if (!skb) {
-		put_page(rinfo->page);
+		put_page(virt_to_page(data));
 		return NULL;
 	}
 
-	/* Set correct skb->data */
-	skb_reserve(skb, rinfo->offset + NICVF_RCV_BUF_ALIGN_BYTES);
-
-	prefetch((void *)rb_ptr);
+	prefetch(skb->data);
 	return skb;
 }
 
@@ -196,7 +168,6 @@ static void nicvf_free_rbdr(struct nicvf *nic, struct rbdr *rbdr)
 	int head, tail;
 	u64 buf_addr;
 	struct rbdr_entry_t *desc;
-	struct rbuf_info *rinfo;
 
 	if (!rbdr)
 		return;
@@ -212,16 +183,14 @@ static void nicvf_free_rbdr(struct nicvf *nic, struct rbdr *rbdr)
 	while (head != tail) {
 		desc = GET_RBDR_DESC(rbdr, head);
 		buf_addr = desc->buf_addr << NICVF_RCV_BUF_ALIGN;
-		rinfo = GET_RBUF_INFO((u64)phys_to_virt(buf_addr));
-		put_page(rinfo->page);
+		put_page(virt_to_page(phys_to_virt(buf_addr)));
 		head++;
 		head &= (rbdr->dmem.q_len - 1);
 	}
 	/* Free SKB of tail desc */
 	desc = GET_RBDR_DESC(rbdr, tail);
 	buf_addr = desc->buf_addr << NICVF_RCV_BUF_ALIGN;
-	rinfo = GET_RBUF_INFO((u64)phys_to_virt(buf_addr));
-	put_page(rinfo->page);
+	put_page(virt_to_page(phys_to_virt(buf_addr)));
 
 	/* Free RBDR ring */
 	nicvf_free_q_desc_mem(nic, &rbdr->dmem);
diff --git a/drivers/net/ethernet/cavium/thunder/nicvf_queues.h b/drivers/net/ethernet/cavium/thunder/nicvf_queues.h
index 033e830..a4f6667 100644
--- a/drivers/net/ethernet/cavium/thunder/nicvf_queues.h
+++ b/drivers/net/ethernet/cavium/thunder/nicvf_queues.h
@@ -83,10 +83,8 @@
 #define MAX_RCV_BUF_COUNT	(1ULL << (RBDR_SIZE6 + 13))
 #define RBDR_THRESH		(RCV_BUF_COUNT / 2)
 #define DMA_BUFFER_LEN		2048 /* In multiples of 128bytes */
-#define RCV_FRAG_LEN	(SKB_DATA_ALIGN(DMA_BUFFER_LEN + NET_SKB_PAD) + \
-			 SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) + \
-			 (NICVF_RCV_BUF_ALIGN_BYTES * 2))
-#define RCV_DATA_OFFSET		NICVF_RCV_BUF_ALIGN_BYTES
+#define RCV_FRAG_LEN	 (SKB_DATA_ALIGN(DMA_BUFFER_LEN + NET_SKB_PAD) + \
+			 SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
 
 #define MAX_CQES_FOR_TX		((SND_QUEUE_LEN / MIN_SQ_DESC_PER_PKT_XMIT) * \
 				 MAX_CQE_PER_PKT_XMIT)
@@ -108,10 +106,6 @@
 #define NICVF_SQ_BASE_ALIGN_BYTES	128  /* 7 bits */
 
 #define NICVF_ALIGNED_ADDR(ADDR, ALIGN_BYTES)	ALIGN(ADDR, ALIGN_BYTES)
-#define NICVF_ADDR_ALIGN_LEN(ADDR, BYTES)\
-	(NICVF_ALIGNED_ADDR(ADDR, BYTES) - BYTES)
-#define NICVF_RCV_BUF_ALIGN_LEN(X)\
-	(NICVF_ALIGNED_ADDR(X, NICVF_RCV_BUF_ALIGN_BYTES) - X)
 
 /* Queue enable/disable */
 #define NICVF_SQ_EN		BIT_ULL(19)
-- 
1.7.1

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