stmmac: Configure Flow Control to work correctly based on rxfifo size

Configure flow control correctly, and based on the receive fifo size read
as a property from the devicetree since the Synopsys stmmac fifo sizes are
configurable based on a particular chip's implementation. This patch maintains
the previous incorrect behavior unless the receive fifo size is found in the
devicetree.

Signed-off-by: Vince Bridgers <vbridger@opensource.altera.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 25 insertions, 1 deletions

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c
index 59d92e811750..0e8937c1184a 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c
@@ -106,8 +106,29 @@ static int dwmac1000_dma_init(void __iomem *ioaddr, int pbl, int fb, int mb,
 	return 0;
 }
 
+static u32 dwmac1000_configure_fc(u32 csr6, int rxfifosz)
+{
+	csr6 &= ~DMA_CONTROL_RFA_MASK;
+	csr6 &= ~DMA_CONTROL_RFD_MASK;
+
+	/* Leave flow control disabled if receive fifo size is less than
+	 * 4K or 0. Otherwise, send XOFF when fifo is 1K less than full,
+	 * and send XON when 2K less than full.
+	 */
+	if (rxfifosz < 4096) {
+		csr6 &= ~DMA_CONTROL_EFC;
+		pr_debug("GMAC: disabling flow control, rxfifo too small(%d)\n",
+			 rxfifosz);
+	} else {
+		csr6 |= DMA_CONTROL_EFC;
+		csr6 |= RFA_FULL_MINUS_1K;
+		csr6 |= RFD_FULL_MINUS_2K;
+	}
+	return csr6;
+}
+
 static void dwmac1000_dma_operation_mode(void __iomem *ioaddr, int txmode,
-					 int rxmode)
+					 int rxmode, int rxfifosz)
 {
 	u32 csr6 = readl(ioaddr + DMA_CONTROL);
 
@@ -153,6 +174,9 @@ static void dwmac1000_dma_operation_mode(void __iomem *ioaddr, int txmode,
 			csr6 |= DMA_CONTROL_RTC_128;
 	}
 
+	/* Configure flow control based on rx fifo size */
+	csr6 = dwmac1000_configure_fc(csr6, rxfifosz);
+
 	writel(csr6, ioaddr + DMA_CONTROL);
 }