[PATCH/RFC 3/5] ravb: Add support for explicit internal clock delay configuration

[Geert Uytterhoeven <geert+renesas@glider.be>]

Some EtherAVB variants support internal clock delay configuration, which
can add larger delays than the delays that are typically supported by
the PHY (using an "rgmii-*id" PHY mode, and/or "[rt]xc-skew-ps"
properties).

Historically, the EtherAVB driver configured these delays based on the
"rgmii-*id" PHY mode.  This caused issues with PHY drivers that
implement PHY internal delays properly[1].  Hence a backwards-compatible
workaround was added by masking the PHY mode[2].

Add proper support for explicit configuration of the MAC internal clock
delays using the new "renesas,[rt]xc-delay-ps" properties.
Fall back to the old handling if none of these properties is present.

[1] Commit bcf3440c6dd78bfe ("net: phy: micrel: add phy-mode support for
    the KSZ9031 PHY")
[2] Commit 9b23203c32ee02cd ("ravb: Mask PHY mode to avoid inserting
    delays twice").

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
 drivers/net/ethernet/renesas/ravb.h      |  1 +
 drivers/net/ethernet/renesas/ravb_main.c | 35 ++++++++++++++++++------
 2 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
index e5ca12ce93c730a9..7453b17a37a2c8d0 100644
--- a/drivers/net/ethernet/renesas/ravb.h
+++ b/drivers/net/ethernet/renesas/ravb.h
@@ -1038,6 +1038,7 @@ struct ravb_private {
 	unsigned wol_enabled:1;
 	unsigned rxcidm:1;		/* RX Clock Internal Delay Mode */
 	unsigned txcidm:1;		/* TX Clock Internal Delay Mode */
+	unsigned rgmii_override:1;	/* Deprecated rgmii-*id behavior */
 	int num_tx_desc;		/* TX descriptors per packet */
 };
 
diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index f326234d1940f43e..0582846bec7726b6 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -1034,11 +1034,7 @@ static int ravb_phy_init(struct net_device *ndev)
 		pn = of_node_get(np);
 	}
 
-	iface = priv->phy_interface;
-	if (priv->chip_id != RCAR_GEN2 && phy_interface_mode_is_rgmii(iface)) {
-		/* ravb_set_delay_mode() takes care of internal delay mode */
-		iface = PHY_INTERFACE_MODE_RGMII;
-	}
+	iface = priv->rgmii_override ? PHY_INTERFACE_MODE_RGMII : priv->phy_interface;
 	phydev = of_phy_connect(ndev, pn, ravb_adjust_link, 0, iface);
 	of_node_put(pn);
 	if (!phydev) {
@@ -1967,20 +1963,41 @@ static const struct soc_device_attribute ravb_delay_mode_quirk_match[] = {
 };
 
 /* Set tx and rx clock internal delay modes */
-static void ravb_parse_delay_mode(struct net_device *ndev)
+static void ravb_parse_delay_mode(struct device_node *np, struct net_device *ndev)
 {
 	struct ravb_private *priv = netdev_priv(ndev);
+	bool explicit_delay = false;
+	u32 delay;
+
+	if (!of_property_read_u32(np, "renesas,rxc-delay-ps", &delay)) {
+		/* Valid values are 0 and 1800, according to DT bindings */
+		priv->rxcidm = !!delay;
+		explicit_delay = true;
+	}
+	if (!of_property_read_u32(np, "renesas,txc-delay-ps", &delay)) {
+		/* Valid values are 0 and 2000, according to DT bindings */
+		priv->txcidm = !!delay;
+		explicit_delay = true;
+	}
 
+	if (explicit_delay)
+		return;
+
+	/* Fall back to legacy rgmii-*id behavior */
 	if (priv->phy_interface == PHY_INTERFACE_MODE_RGMII_ID ||
-	    priv->phy_interface == PHY_INTERFACE_MODE_RGMII_RXID)
+	    priv->phy_interface == PHY_INTERFACE_MODE_RGMII_RXID) {
 		priv->rxcidm = true;
+		priv->rgmii_override = true;
+	}
 
 	if (priv->phy_interface == PHY_INTERFACE_MODE_RGMII_ID ||
 	    priv->phy_interface == PHY_INTERFACE_MODE_RGMII_TXID) {
 		if (!WARN(soc_device_match(ravb_delay_mode_quirk_match),
 			  "phy-mode %s requires TX clock internal delay mode which is not supported by this hardware revision. Please update device tree",
-			  phy_modes(priv->phy_interface)))
+			  phy_modes(priv->phy_interface))) {
 			priv->txcidm = true;
+			priv->rgmii_override = true;
+		}
 	}
 }
 
@@ -2126,7 +2143,7 @@ static int ravb_probe(struct platform_device *pdev)
 	ravb_modify(ndev, GCCR, GCCR_LTI, GCCR_LTI);
 
 	if (priv->chip_id != RCAR_GEN2) {
-		ravb_parse_delay_mode(ndev);
+		ravb_parse_delay_mode(np, ndev);
 		ravb_set_delay_mode(ndev);
 	}
 
-- 
2.17.1