[PATCH v3 net-next 01/12] net: stmmac: Enable OSP for GMAC4

[Jose Abreu <Jose.Abreu@synopsys.com>]

This enables OSP (Operate on Second Packet) for GMAC4. The feature
allows DMA to fetch second descriptor while its still processing the
first one.

Running iperf, the performance gain is +/- 38%.

Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Joao Pinto <jpinto@synopsys.com>
Cc: Vitor Soares <soares@synopsys.com>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c
index 117c3a5..9aab5b3 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c
@@ -94,6 +94,10 @@ static void dwmac4_dma_init_tx_chan(void __iomem *ioaddr,
 
 	value = readl(ioaddr + DMA_CHAN_TX_CONTROL(chan));
 	value = value | (txpbl << DMA_BUS_MODE_PBL_SHIFT);
+
+	/* Enable OSP to get best performance */
+	value |= DMA_CONTROL_OSP;
+
 	writel(value, ioaddr + DMA_CHAN_TX_CONTROL(chan));
 
 	writel(dma_tx_phy, ioaddr + DMA_CHAN_TX_BASE_ADDR(chan));
-- 
1.7.1