stmmac: add mixed burst for DMA

In mixed burst (MB) mode, the AHB master always initiates
the bursts with fixed-size when the DMA requests transfers
of size less than or equal to 16 beats.
This patch adds the MB support and the flag that can be
passed from the platform to select it.
MB mode can also give some benefits in terms of performances
on some platforms.

v2: fixed Coding Style

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

6 files changed, 13 insertions, 5 deletions

diff --git a/drivers/net/ethernet/stmicro/stmmac/common.h b/drivers/net/ethernet/stmicro/stmmac/common.h
index 7164509e3832..bcd54d6e94fd 100644
--- a/drivers/net/ethernet/stmicro/stmmac/common.h
+++ b/drivers/net/ethernet/stmicro/stmmac/common.h
@@ -247,8 +247,8 @@ struct stmmac_desc_ops {
 
 struct stmmac_dma_ops {
 	/* DMA core initialization */
-	int (*init) (void __iomem *ioaddr, int pbl, int fb, int burst_len,
-			u32 dma_tx, u32 dma_rx);
+	int (*init) (void __iomem *ioaddr, int pbl, int fb, int mb,
+		     int burst_len, u32 dma_tx, u32 dma_rx);
 	/* Dump DMA registers */
 	void (*dump_regs) (void __iomem *ioaddr);
 	/* Set tx/rx threshold in the csr6 register
diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac1000.h b/drivers/net/ethernet/stmicro/stmmac/dwmac1000.h
index 1527f4ecd11a..23478bf4ed7a 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac1000.h
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac1000.h
@@ -141,6 +141,7 @@ enum rx_tx_priority_ratio {
 };
 
 #define DMA_BUS_MODE_FB		0x00010000	/* Fixed burst */
+#define DMA_BUS_MODE_MB		0x04000000	/* Mixed burst */
 #define DMA_BUS_MODE_RPBL_MASK	0x003e0000	/* Rx-Programmable Burst Len */
 #define DMA_BUS_MODE_RPBL_SHIFT	17
 #define DMA_BUS_MODE_USP	0x00800000
diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c
index 3675c5731565..033500090f55 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c
@@ -31,7 +31,7 @@
 #include "dwmac_dma.h"
 
 static int dwmac1000_dma_init(void __iomem *ioaddr, int pbl, int fb,
-			      int burst_len, u32 dma_tx, u32 dma_rx)
+			      int mb, int burst_len, u32 dma_tx, u32 dma_rx)
 {
 	u32 value = readl(ioaddr + DMA_BUS_MODE);
 	int limit;
@@ -66,6 +66,10 @@ static int dwmac1000_dma_init(void __iomem *ioaddr, int pbl, int fb,
 	if (fb)
 		value |= DMA_BUS_MODE_FB;
 
+	/* Mixed Burst has no effect when fb is set */
+	if (mb)
+		value |= DMA_BUS_MODE_MB;
+
 #ifdef CONFIG_STMMAC_DA
 	value |= DMA_BUS_MODE_DA;	/* Rx has priority over tx */
 #endif
diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac100_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwmac100_dma.c
index 92ed2e07609e..c2b4d55a79b6 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac100_dma.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac100_dma.c
@@ -33,7 +33,7 @@
 #include "dwmac_dma.h"
 
 static int dwmac100_dma_init(void __iomem *ioaddr, int pbl, int fb,
-			     int burst_len, u32 dma_tx, u32 dma_rx)
+			     int mb, int burst_len, u32 dma_tx, u32 dma_rx)
 {
 	u32 value = readl(ioaddr + DMA_BUS_MODE);
 	int limit;
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index a9699ae49add..d1d084018877 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -925,6 +925,7 @@ static void stmmac_check_ether_addr(struct stmmac_priv *priv)
 static int stmmac_init_dma_engine(struct stmmac_priv *priv)
 {
 	int pbl = DEFAULT_DMA_PBL, fixed_burst = 0, burst_len = 0;
+	int mixed_burst = 0;
 
 	/* Some DMA parameters can be passed from the platform;
 	 * in case of these are not passed we keep a default
@@ -932,10 +933,11 @@ static int stmmac_init_dma_engine(struct stmmac_priv *priv)
 	if (priv->plat->dma_cfg) {
 		pbl = priv->plat->dma_cfg->pbl;
 		fixed_burst = priv->plat->dma_cfg->fixed_burst;
+		mixed_burst = priv->plat->dma_cfg->mixed_burst;
 		burst_len = priv->plat->dma_cfg->burst_len;
 	}
 
-	return priv->hw->dma->init(priv->ioaddr, pbl, fixed_burst,
+	return priv->hw->dma->init(priv->ioaddr, pbl, fixed_burst, mixed_burst,
 				   burst_len, priv->dma_tx_phy,
 				   priv->dma_rx_phy);
 }
diff --git a/include/linux/stmmac.h b/include/linux/stmmac.h
index f85c93d6e6da..b69bdb1e08b6 100644
--- a/include/linux/stmmac.h
+++ b/include/linux/stmmac.h
@@ -86,6 +86,7 @@ struct stmmac_mdio_bus_data {
 struct stmmac_dma_cfg {
 	int pbl;
 	int fixed_burst;
+	int mixed_burst;
 	int burst_len;
 };