net: ethernet: stmmac: reset force speed bit for ipq806x

Some bootloader may set the force speed regs even if the actual
interface should use autonegotiation between PCS and PHY.
This cause the complete malfuction of the interface.

To fix this correctly reset the force speed regs if a fixed-link is not
defined in the DTS. With a fixed-link node correctly configure the
forced speed regs to handle any misconfiguration by the bootloader.

Reported-by: Mark Mentovai <[e-mail]>
Co-developed-by: Mark Mentovai <[e-mail]>
Signed-off-by: Mark Mentovai <[e-mail]>
Signed-off-by: Christian 'Ansuel' Marangi <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Paolo Abeni <[e-mail]>

drivers/net/ethernet/stmicro/stmmac/dwmac-ipq806x.c

···
 #define NSS_COMMON_CLK_DIV_SGMII_100		4
 #define NSS_COMMON_CLK_DIV_SGMII_10		49
 
+#define QSGMII_PCS_ALL_CH_CTL			0x80
+#define QSGMII_PCS_CH_SPEED_FORCE		BIT(1)
+#define QSGMII_PCS_CH_SPEED_10			0x0
+#define QSGMII_PCS_CH_SPEED_100			BIT(2)
+#define QSGMII_PCS_CH_SPEED_1000		BIT(3)
+#define QSGMII_PCS_CH_SPEED_MASK		(QSGMII_PCS_CH_SPEED_FORCE | \
+						 QSGMII_PCS_CH_SPEED_10 | \
+						 QSGMII_PCS_CH_SPEED_100 | \
+						 QSGMII_PCS_CH_SPEED_1000)
+#define QSGMII_PCS_CH_SPEED_SHIFT(x)		((x) * 4)
+
 #define QSGMII_PCS_CAL_LCKDT_CTL		0x120
 #define QSGMII_PCS_CAL_LCKDT_CTL_RST		BIT(19)
 
···
 	ipq806x_gmac_set_speed(gmac, speed);
 }
 
+static int
+ipq806x_gmac_configure_qsgmii_pcs_speed(struct ipq806x_gmac *gmac)
+{
+	struct platform_device *pdev = gmac->pdev;
+	struct device *dev = &pdev->dev;
+	struct device_node *dn;
+	int link_speed;
+	int val = 0;
+	int ret;
+
+	/* Some bootloader may apply wrong configuration and cause
+	 * not functioning port. If fixed link is not set,
+	 * reset the force speed bit.
+	 */
+	if (!of_phy_is_fixed_link(pdev->dev.of_node))
+		goto write;
+
+	dn = of_get_child_by_name(pdev->dev.of_node, "fixed-link");
+	ret = of_property_read_u32(dn, "speed", &link_speed);
+	of_node_put(dn);
+	if (ret) {
+		dev_err(dev, "found fixed-link node with no speed");
+		return ret;
+	}
+
+	val = QSGMII_PCS_CH_SPEED_FORCE;
+
+	switch (link_speed) {
+	case SPEED_1000:
+		val |= QSGMII_PCS_CH_SPEED_1000;
+		break;
+	case SPEED_100:
+		val |= QSGMII_PCS_CH_SPEED_100;
+		break;
+	case SPEED_10:
+		val |= QSGMII_PCS_CH_SPEED_10;
+		break;
+	}
+
+write:
+	regmap_update_bits(gmac->qsgmii_csr, QSGMII_PCS_ALL_CH_CTL,
+			   QSGMII_PCS_CH_SPEED_MASK <<
+			   QSGMII_PCS_CH_SPEED_SHIFT(gmac->id),
+			   val <<
+			   QSGMII_PCS_CH_SPEED_SHIFT(gmac->id));
+
+	return 0;
+}
+
 static const struct soc_device_attribute ipq806x_gmac_soc_v1[] = {
 	{
 		.revision = "1.*",
···
 
 	if (gmac->phy_mode == PHY_INTERFACE_MODE_SGMII) {
 		err = ipq806x_gmac_configure_qsgmii_params(gmac);
+		if (err)
+			goto err_remove_config_dt;
+
+		err = ipq806x_gmac_configure_qsgmii_pcs_speed(gmac);
 		if (err)
 			goto err_remove_config_dt;
 	}