Merge branch 'stmmac-Enable-Flow-Control'

Jose Abreu says:

====================
net: stmmac: Enable Flow Control

I don't know of any specific reason why Flow Control is off by default but
do let me know if there is any.

Tested in B2B between XGMAC2 and GMAC5.
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/dwxgmac2.h

@@ -143,6 +143,11 @@
 #define XGMAC_RSF			BIT(5)
 #define XGMAC_RTC			GENMASK(1, 0)
 #define XGMAC_RTC_SHIFT			0
+#define XGMAC_MTL_RXQ_FLOW_CONTROL(x)	(0x00001150 + (0x80 * (x)))
+#define XGMAC_RFD			GENMASK(31, 17)
+#define XGMAC_RFD_SHIFT			17
+#define XGMAC_RFA			GENMASK(15, 1)
+#define XGMAC_RFA_SHIFT			1
 #define XGMAC_MTL_QINTEN(x)		(0x00001170 + (0x80 * (x)))
 #define XGMAC_RXOIE			BIT(16)
 #define XGMAC_MTL_QINT_STATUS(x)	(0x00001174 + (0x80 * (x)))

drivers/net/ethernet/stmicro/stmmac/dwxgmac2_dma.c

@@ -147,6 +147,52 @@ static void dwxgmac2_dma_rx_mode(void __iomem *ioaddr, int mode,
 	value &= ~XGMAC_RQS;
 	value |= (rqs << XGMAC_RQS_SHIFT) & XGMAC_RQS;
 
+	if ((fifosz >= 4096) && (qmode != MTL_QUEUE_AVB)) {
+		u32 flow = readl(ioaddr + XGMAC_MTL_RXQ_FLOW_CONTROL(channel));
+		unsigned int rfd, rfa;
+
+		value |= XGMAC_EHFC;
+
+		/* Set Threshold for Activating Flow Control to min 2 frames,
+		 * i.e. 1500 * 2 = 3000 bytes.
+		 *
+		 * Set Threshold for Deactivating Flow Control to min 1 frame,
+		 * i.e. 1500 bytes.
+		 */
+		switch (fifosz) {
+		case 4096:
+			/* This violates the above formula because of FIFO size
+			 * limit therefore overflow may occur in spite of this.
+			 */
+			rfd = 0x03; /* Full-2.5K */
+			rfa = 0x01; /* Full-1.5K */
+			break;
+
+		case 8192:
+			rfd = 0x06; /* Full-4K */
+			rfa = 0x0a; /* Full-6K */
+			break;
+
+		case 16384:
+			rfd = 0x06; /* Full-4K */
+			rfa = 0x12; /* Full-10K */
+			break;
+
+		default:
+			rfd = 0x06; /* Full-4K */
+			rfa = 0x1e; /* Full-16K */
+			break;
+		}
+
+		flow &= ~XGMAC_RFD;
+		flow |= rfd << XGMAC_RFD_SHIFT;
+
+		flow &= ~XGMAC_RFA;
+		flow |= rfa << XGMAC_RFA_SHIFT;
+
+		writel(flow, ioaddr + XGMAC_MTL_RXQ_FLOW_CONTROL(channel));
+	}
+
 	writel(value, ioaddr + XGMAC_MTL_RXQ_OPMODE(channel));
 
 	/* Enable MTL RX overflow */

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -74,7 +74,7 @@ MODULE_PARM_DESC(phyaddr, "Physical device address");
 #define STMMAC_TX_THRESH	(DMA_TX_SIZE / 4)
 #define STMMAC_RX_THRESH	(DMA_RX_SIZE / 4)
 
-static int flow_ctrl = FLOW_OFF;
+static int flow_ctrl = FLOW_AUTO;
 module_param(flow_ctrl, int, 0644);
 MODULE_PARM_DESC(flow_ctrl, "Flow control ability [on/off]");