drivers: net: xgene: Add support RGMII TX/RX delay configuration

Add RGMII TX/RX delay configuration support. RGMII standard requires 2ns
delay to help the RGMII bridge receiver to sample data correctly. If the
default value does not provide proper centering of the data sample, the
TX/RX delay parameters can be used to adjust accordingly.

Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/apm/xgene/xgene_enet_hw.c

@@ -461,6 +461,7 @@ static void xgene_gmac_reset(struct xgene_enet_pdata *pdata)
 
 static void xgene_gmac_init(struct xgene_enet_pdata *pdata)
 {
+	struct device *dev = &pdata->pdev->dev;
 	u32 value, mc2;
 	u32 intf_ctl, rgmii;
 	u32 icm0, icm2;
@@ -490,7 +491,12 @@ static void xgene_gmac_init(struct xgene_enet_pdata *pdata)
 	default:
 		ENET_INTERFACE_MODE2_SET(&mc2, 2);
 		intf_ctl |= ENET_GHD_MODE;
-		CFG_TXCLK_MUXSEL0_SET(&rgmii, 4);
+
+		if (dev->of_node) {
+			CFG_TXCLK_MUXSEL0_SET(&rgmii, pdata->tx_delay);
+			CFG_RXCLK_MUXSEL0_SET(&rgmii, pdata->rx_delay);
+		}
+
 		xgene_enet_rd_csr(pdata, DEBUG_REG_ADDR, &value);
 		value |= CFG_BYPASS_UNISEC_TX | CFG_BYPASS_UNISEC_RX;
 		xgene_enet_wr_csr(pdata, DEBUG_REG_ADDR, value);

drivers/net/ethernet/apm/xgene/xgene_enet_hw.h

@@ -144,6 +144,7 @@ enum xgene_enet_rm {
 #define CFG_BYPASS_UNISEC_RX		BIT(1)
 #define CFG_CLE_BYPASS_EN0		BIT(31)
 #define CFG_TXCLK_MUXSEL0_SET(dst, val)	xgene_set_bits(dst, val, 29, 3)
+#define CFG_RXCLK_MUXSEL0_SET(dst, val)	xgene_set_bits(dst, val, 26, 3)
 
 #define CFG_CLE_IP_PROTOCOL0_SET(dst, val)	xgene_set_bits(dst, val, 16, 2)
 #define CFG_CLE_DSTQID0_SET(dst, val)		xgene_set_bits(dst, val, 0, 12)

drivers/net/ethernet/apm/xgene/xgene_enet_main.c

@@ -1118,6 +1118,47 @@ static int xgene_get_port_id_dt(struct device *dev, struct xgene_enet_pdata *pda
 	return ret;
 }
 
+static int xgene_get_tx_delay(struct xgene_enet_pdata *pdata)
+{
+	struct device *dev = &pdata->pdev->dev;
+	int delay, ret;
+
+	ret = of_property_read_u32(dev->of_node, "tx-delay", &delay);
+	if (ret) {
+		pdata->tx_delay = 4;
+		return 0;
+	}
+
+	if (delay < 0 || delay > 7) {
+		dev_err(dev, "Invalid tx-delay specified\n");
+		return -EINVAL;
+	}
+
+	pdata->tx_delay = delay;
+
+	return 0;
+}
+
+static int xgene_get_rx_delay(struct xgene_enet_pdata *pdata)
+{
+	struct device *dev = &pdata->pdev->dev;
+	int delay, ret;
+
+	ret = of_property_read_u32(dev->of_node, "rx-delay", &delay);
+	if (ret) {
+		pdata->rx_delay = 2;
+		return 0;
+	}
+
+	if (delay < 0 || delay > 7) {
+		dev_err(dev, "Invalid rx-delay specified\n");
+		return -EINVAL;
+	}
+
+	pdata->rx_delay = delay;
+
+	return 0;
+}
 
 static int xgene_enet_get_resources(struct xgene_enet_pdata *pdata)
 {
@@ -1194,6 +1235,14 @@ static int xgene_enet_get_resources(struct xgene_enet_pdata *pdata)
 		return -ENODEV;
 	}
 
+	ret = xgene_get_tx_delay(pdata);
+	if (ret)
+		return ret;
+
+	ret = xgene_get_rx_delay(pdata);
+	if (ret)
+		return ret;
+
 	ret = platform_get_irq(pdev, 0);
 	if (ret <= 0) {
 		dev_err(dev, "Unable to get ENET Rx IRQ\n");

drivers/net/ethernet/apm/xgene/xgene_enet_main.h

@@ -184,6 +184,8 @@ struct xgene_enet_pdata {
 	u8 bp_bufnum;
 	u16 ring_num;
 	u32 mss;
+	u8 tx_delay;
+	u8 rx_delay;
 };
 
 struct xgene_indirect_ctl {