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Date: Wed, 9 Dec 2015 09:37:40 +0100
From: Giuseppe Cavallaro <peppe.cavallaro@...com>
To: <netdev@...r.kernel.org>
CC: <alexandre.torgue@...com>,
Giuseppe Cavallaro <peppe.cavallaro@...com>,
David McKay <david.mckay@...com>
Subject: [PATCH (net-next.git) 04/18] stmmac: remove modulo in stmmac_xmit()
The indexes into the ring buffer are always incremented, and
the entry is accessed via doing a modulo to find the "real" index.
I have changed this for 3 reasons:
* It is inefficient, modulo is an expensive operation.
* It is also broken when the counter wraps.
* It makes my head hurt trying to cope with huge numbers
This patch replaces the modulo with a simple if clamp.
Signed-off-by: David McKay <david.mckay@...com>
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@...com>
---
drivers/net/ethernet/stmicro/stmmac/chain_mode.c | 15 ++++++----
drivers/net/ethernet/stmicro/stmmac/ring_mode.c | 7 +++-
drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 31 +++++++++++++++-----
3 files changed, 37 insertions(+), 16 deletions(-)
diff --git a/drivers/net/ethernet/stmicro/stmmac/chain_mode.c b/drivers/net/ethernet/stmicro/stmmac/chain_mode.c
index cf28dab..399a7ed 100644
--- a/drivers/net/ethernet/stmicro/stmmac/chain_mode.c
+++ b/drivers/net/ethernet/stmicro/stmmac/chain_mode.c
@@ -32,7 +32,7 @@ static int stmmac_jumbo_frm(void *p, struct sk_buff *skb, int csum)
{
struct stmmac_priv *priv = (struct stmmac_priv *)p;
unsigned int txsize = priv->dma_tx_size;
- unsigned int entry = priv->cur_tx % txsize;
+ unsigned int entry = priv->cur_tx;
struct dma_desc *desc = priv->dma_tx + entry;
unsigned int nopaged_len = skb_headlen(skb);
unsigned int bmax;
@@ -54,7 +54,8 @@ static int stmmac_jumbo_frm(void *p, struct sk_buff *skb, int csum)
while (len != 0) {
priv->tx_skbuff[entry] = NULL;
- entry = (++priv->cur_tx) % txsize;
+ if (++entry >= txsize)
+ entry = 0;
desc = priv->dma_tx + entry;
if (len > bmax) {
@@ -82,6 +83,9 @@ static int stmmac_jumbo_frm(void *p, struct sk_buff *skb, int csum)
len = 0;
}
}
+
+ priv->cur_tx = entry;
+
return entry;
}
@@ -151,10 +155,9 @@ static void stmmac_clean_desc3(void *priv_ptr, struct dma_desc *p)
* 1588-2002 time stamping is enabled, hence reinitialize it
* to keep explicit chaining in the descriptor.
*/
- p->des3 = (unsigned int)(priv->dma_tx_phy +
- (((priv->dirty_tx + 1) %
- priv->dma_tx_size) *
- sizeof(struct dma_desc)));
+ p->des3 = (unsigned int)((priv->dma_tx_phy +
+ priv->dirty_tx + 1) *
+ sizeof(struct dma_desc));
}
const struct stmmac_mode_ops chain_mode_ops = {
diff --git a/drivers/net/ethernet/stmicro/stmmac/ring_mode.c b/drivers/net/ethernet/stmicro/stmmac/ring_mode.c
index 5dd50c6..2560855 100644
--- a/drivers/net/ethernet/stmicro/stmmac/ring_mode.c
+++ b/drivers/net/ethernet/stmicro/stmmac/ring_mode.c
@@ -32,7 +32,7 @@ static int stmmac_jumbo_frm(void *p, struct sk_buff *skb, int csum)
{
struct stmmac_priv *priv = (struct stmmac_priv *)p;
unsigned int txsize = priv->dma_tx_size;
- unsigned int entry = priv->cur_tx % txsize;
+ unsigned int entry = priv->cur_tx;
struct dma_desc *desc;
unsigned int nopaged_len = skb_headlen(skb);
unsigned int bmax, len;
@@ -62,7 +62,8 @@ static int stmmac_jumbo_frm(void *p, struct sk_buff *skb, int csum)
STMMAC_RING_MODE);
wmb();
priv->tx_skbuff[entry] = NULL;
- entry = (++priv->cur_tx) % txsize;
+ if (++entry >= txsize)
+ entry = 0;
if (priv->extend_desc)
desc = (struct dma_desc *)(priv->dma_etx + entry);
@@ -90,6 +91,8 @@ static int stmmac_jumbo_frm(void *p, struct sk_buff *skb, int csum)
STMMAC_RING_MODE);
}
+ priv->cur_tx = entry;
+
return entry;
}
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 2dd0279..366da1f 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -201,7 +201,14 @@ static void print_pkt(unsigned char *buf, int len)
static inline u32 stmmac_tx_avail(struct stmmac_priv *priv)
{
- return priv->dirty_tx + priv->dma_tx_size - priv->cur_tx - 1;
+ unsigned avail;
+
+ if (priv->dirty_tx > priv->cur_tx)
+ avail = priv->dirty_tx - priv->cur_tx - 1;
+ else
+ avail = priv->dma_tx_size - priv->cur_tx + priv->dirty_tx - 1;
+
+ return avail;
}
/**
@@ -1315,16 +1322,16 @@ static void stmmac_dma_operation_mode(struct stmmac_priv *priv)
*/
static void stmmac_tx_clean(struct stmmac_priv *priv)
{
- unsigned int txsize = priv->dma_tx_size;
unsigned int bytes_compl = 0, pkts_compl = 0;
+ unsigned int txsize = priv->dma_tx_size;
+ unsigned int entry = priv->dirty_tx;
spin_lock(&priv->tx_lock);
priv->xstats.tx_clean++;
- while (priv->dirty_tx != priv->cur_tx) {
+ while (entry != priv->cur_tx) {
int last;
- unsigned int entry = priv->dirty_tx % txsize;
struct sk_buff *skb = priv->tx_skbuff[entry];
struct dma_desc *p;
@@ -1381,7 +1388,9 @@ static void stmmac_tx_clean(struct stmmac_priv *priv)
priv->hw->desc->release_tx_desc(p, priv->mode);
- priv->dirty_tx++;
+ if (++entry >= txsize)
+ entry = 0;
+ priv->dirty_tx = entry;
}
netdev_completed_queue(priv->dev, pkts_compl, bytes_compl);
@@ -1981,7 +1990,8 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
if (priv->tx_path_in_lpi_mode)
stmmac_disable_eee_mode(priv);
- entry = priv->cur_tx % txsize;
+ entry = priv->cur_tx;
+
csum_insertion = (skb->ip_summed == CHECKSUM_PARTIAL);
@@ -2016,7 +2026,9 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
int len = skb_frag_size(frag);
priv->tx_skbuff[entry] = NULL;
- entry = (++priv->cur_tx) % txsize;
+ if (++entry >= txsize)
+ entry = 0;
+
if (priv->extend_desc)
desc = (struct dma_desc *)(priv->dma_etx + entry);
else
@@ -2059,7 +2071,10 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
priv->hw->desc->set_tx_owner(first);
wmb();
- priv->cur_tx++;
+ if (++entry >= txsize)
+ entry = 0;
+
+ priv->cur_tx = entry;
if (netif_msg_pktdata(priv)) {
pr_debug("%s: curr %d dirty=%d entry=%d, first=%p, nfrags=%d",
--
1.7.4.4
--
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