net: dsa: qca8k: add support for sgmii falling edge

Add support for this in the qca8k driver. Also add support for SGMII
rx/tx clock falling edge. This is only present for pad0, pad5 and
pad6 have these bit reserved from Documentation. Add a comment that this
is hardcoded to PAD0 as qca8327/28/34/37 have an unique sgmii line and
setting falling in port0 applies to both configuration with sgmii used
for port0 or port6.

Co-developed-by: Matthew Hagan <mnhagan88@gmail.com>
Signed-off-by: Matthew Hagan <mnhagan88@gmail.com>
Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/qca8k.c

@@ -977,6 +977,42 @@ qca8k_setup_mac_pwr_sel(struct qca8k_priv *priv)
 	return ret;
 }
 
+static int
+qca8k_parse_port_config(struct qca8k_priv *priv)
+{
+	struct device_node *port_dn;
+	phy_interface_t mode;
+	struct dsa_port *dp;
+	int port, ret;
+
+	/* We have 2 CPU port. Check them */
+	for (port = 0; port < QCA8K_NUM_PORTS; port++) {
+		/* Skip every other port */
+		if (port != 0 && port != 6)
+			continue;
+
+		dp = dsa_to_port(priv->ds, port);
+		port_dn = dp->dn;
+
+		if (!of_device_is_available(port_dn))
+			continue;
+
+		ret = of_get_phy_mode(port_dn, &mode);
+		if (ret)
+			continue;
+
+		if (mode == PHY_INTERFACE_MODE_SGMII) {
+			if (of_property_read_bool(port_dn, "qca,sgmii-txclk-falling-edge"))
+				priv->sgmii_tx_clk_falling_edge = true;
+
+			if (of_property_read_bool(port_dn, "qca,sgmii-rxclk-falling-edge"))
+				priv->sgmii_rx_clk_falling_edge = true;
+		}
+	}
+
+	return 0;
+}
+
 static int
 qca8k_setup(struct dsa_switch *ds)
 {
@@ -990,6 +1026,11 @@ qca8k_setup(struct dsa_switch *ds)
 		return -EINVAL;
 	}
 
+	/* Parse CPU port config to be later used in phy_link mac_config */
+	ret = qca8k_parse_port_config(priv);
+	if (ret)
+		return ret;
+
 	mutex_init(&priv->reg_mutex);
 
 	/* Start by setting up the register mapping */
@@ -1274,6 +1315,28 @@ qca8k_phylink_mac_config(struct dsa_switch *ds, int port, unsigned int mode,
 		}
 
 		qca8k_write(priv, QCA8K_REG_SGMII_CTRL, val);
+
+		/* For qca8327/qca8328/qca8334/qca8338 sgmii is unique and
+		 * falling edge is set writing in the PORT0 PAD reg
+		 */
+		if (priv->switch_id == QCA8K_ID_QCA8327 ||
+		    priv->switch_id == QCA8K_ID_QCA8337)
+			reg = QCA8K_REG_PORT0_PAD_CTRL;
+
+		val = 0;
+
+		/* SGMII Clock phase configuration */
+		if (priv->sgmii_rx_clk_falling_edge)
+			val |= QCA8K_PORT0_PAD_SGMII_RXCLK_FALLING_EDGE;
+
+		if (priv->sgmii_tx_clk_falling_edge)
+			val |= QCA8K_PORT0_PAD_SGMII_TXCLK_FALLING_EDGE;
+
+		if (val)
+			ret = qca8k_rmw(priv, reg,
+					QCA8K_PORT0_PAD_SGMII_RXCLK_FALLING_EDGE |
+					QCA8K_PORT0_PAD_SGMII_TXCLK_FALLING_EDGE,
+					val);
 		break;
 	default:
 		dev_err(ds->dev, "xMII mode %s not supported for port %d\n",

drivers/net/dsa/qca8k.h

@@ -35,6 +35,8 @@
 #define   QCA8K_MASK_CTRL_DEVICE_ID_MASK		GENMASK(15, 8)
 #define   QCA8K_MASK_CTRL_DEVICE_ID(x)			((x) >> 8)
 #define QCA8K_REG_PORT0_PAD_CTRL			0x004
+#define   QCA8K_PORT0_PAD_SGMII_RXCLK_FALLING_EDGE	BIT(19)
+#define   QCA8K_PORT0_PAD_SGMII_TXCLK_FALLING_EDGE	BIT(18)
 #define QCA8K_REG_PORT5_PAD_CTRL			0x008
 #define QCA8K_REG_PORT6_PAD_CTRL			0x00c
 #define   QCA8K_PORT_PAD_RGMII_EN			BIT(26)
@@ -260,6 +262,8 @@ struct qca8k_priv {
 	u8 switch_revision;
 	u8 rgmii_tx_delay;
 	u8 rgmii_rx_delay;
+	bool sgmii_rx_clk_falling_edge;
+	bool sgmii_tx_clk_falling_edge;
 	bool legacy_phy_port_mapping;
 	struct regmap *regmap;
 	struct mii_bus *bus;