ravb: Add tx and rx clock internal delays mode of APSR

This patch enables tx and rx clock internal delay modes (TDM and RDM).

This is to address a failure in the case of 1Gbps communication using the
by salvator-x board with the KSZ9031RNX phy. This has been reported to
occur with both the r8a7795 (H3) and r8a7796 (M3-W) SoCs.

With this change APSR internal delay modes are enabled for
"rgmii-id", "rgmii-rxid" and "rgmii-txid" phy modes as follows:

phy mode   | ASPR delay mode
-----------+----------------
rgmii-id   | TDM and RDM
rgmii-rxid | RDM
rgmii-txid | TDM

Signed-off-by: Kazuya Mizuguchi <kazuya.mizuguchi.ks@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/renesas/ravb.h

@@ -76,6 +76,7 @@ enum ravb_reg {
 	CDAR20	= 0x0060,
 	CDAR21	= 0x0064,
 	ESR	= 0x0088,
+	APSR	= 0x008C,	/* R-Car Gen3 only */
 	RCR	= 0x0090,
 	RQC0	= 0x0094,
 	RQC1	= 0x0098,
@@ -248,6 +249,15 @@ enum ESR_BIT {
 	ESR_EIL		= 0x00001000,
 };
 
+/* APSR */
+enum APSR_BIT {
+	APSR_MEMS		= 0x00000002,
+	APSR_CMSW		= 0x00000010,
+	APSR_DM			= 0x00006000,	/* Undocumented? */
+	APSR_DM_RDM		= 0x00002000,
+	APSR_DM_TDM		= 0x00004000,
+};
+
 /* RCR */
 enum RCR_BIT {
 	RCR_EFFS	= 0x00000001,

drivers/net/ethernet/renesas/ravb_main.c

@@ -1920,6 +1920,23 @@ static void ravb_set_config_mode(struct net_device *ndev)
 	}
 }
 
+/* Set tx and rx clock internal delay modes */
+static void ravb_set_delay_mode(struct net_device *ndev)
+{
+	struct ravb_private *priv = netdev_priv(ndev);
+	int set = 0;
+
+	if (priv->phy_interface == PHY_INTERFACE_MODE_RGMII_ID ||
+	    priv->phy_interface == PHY_INTERFACE_MODE_RGMII_RXID)
+		set |= APSR_DM_RDM;
+
+	if (priv->phy_interface == PHY_INTERFACE_MODE_RGMII_ID ||
+	    priv->phy_interface == PHY_INTERFACE_MODE_RGMII_TXID)
+		set |= APSR_DM_TDM;
+
+	ravb_modify(ndev, APSR, APSR_DM, set);
+}
+
 static int ravb_probe(struct platform_device *pdev)
 {
 	struct device_node *np = pdev->dev.of_node;
@@ -2032,6 +2049,9 @@ static int ravb_probe(struct platform_device *pdev)
 	/* Request GTI loading */
 	ravb_modify(ndev, GCCR, GCCR_LTI, GCCR_LTI);
 
+	if (priv->chip_id != RCAR_GEN2)
+		ravb_set_delay_mode(ndev);
+
 	/* Allocate descriptor base address table */
 	priv->desc_bat_size = sizeof(struct ravb_desc) * DBAT_ENTRY_NUM;
 	priv->desc_bat = dma_alloc_coherent(ndev->dev.parent, priv->desc_bat_size,
@@ -2168,6 +2188,9 @@ static int __maybe_unused ravb_resume(struct device *dev)
 	/* Request GTI loading */
 	ravb_modify(ndev, GCCR, GCCR_LTI, GCCR_LTI);
 
+	if (priv->chip_id != RCAR_GEN2)
+		ravb_set_delay_mode(ndev);
+
 	/* Restore descriptor base address table */
 	ravb_write(ndev, priv->desc_bat_dma, DBAT);