linux-kernel - [PATCH net-next v2 10/10] net: mdio: support C45-over-C22 when probed via OF

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Message-Id: <20230620-feature-c45-over-c22-v2-10-def0ab9ccee2@kernel.org>
Date:   Fri, 23 Jun 2023 12:29:19 +0200
From:   Michael Walle <mwalle@...nel.org>
To:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Yisen Zhuang <yisen.zhuang@...wei.com>,
        Salil Mehta <salil.mehta@...wei.com>,
        Florian Fainelli <florian.fainelli@...adcom.com>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Marek Behún <kabel@...nel.org>,
        Xu Liang <lxu@...linear.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Michael Walle <mwalle@...nel.org>
Subject: [PATCH net-next v2 10/10] net: mdio: support C45-over-C22 when
 probed via OF

Fall back to C45-over-C22 when the MDIO bus isn't capable of doing C45
transfers. This might be the case if there are broken PHYs on the bus or
if the MDIO controller cannot do C45 transactions at all.

For this to work, split the PHY registration into three steps, as done
in the generic PHY probing code:
 (1) add C22 PHYs
 (2) scan for broken C22 PHYs
 (3) add C45 PHYs

If step (2) detects a broken PHY, any PHYs will be added with
C45-over-C22 access in step (3). Step (3) also ensures, that
C45-over-C22 is used if C45 access is not supported at all on the bus.

Signed-off-by: Michael Walle <mwalle@...nel.org>
---
 drivers/net/mdio/of_mdio.c | 63 +++++++++++++++++++++++++++++++++++-----------
 1 file changed, 48 insertions(+), 15 deletions(-)

diff --git a/drivers/net/mdio/of_mdio.c b/drivers/net/mdio/of_mdio.c
index 7eb32ebb846d..e9d3cf6b68ee 100644
--- a/drivers/net/mdio/of_mdio.c
+++ b/drivers/net/mdio/of_mdio.c
@@ -100,6 +100,11 @@ static const struct of_device_id whitelist_phys[] = {
 	{}
 };
 
+static bool of_mdiobus_child_is_c45_phy(struct device_node *child)
+{
+	return of_device_is_compatible(child, "ethernet-phy-ieee802.3-c45");
+}
+
 /*
  * Return true if the child node is for a phy. It must either:
  * o Compatible string of "ethernet-phy-idX.X"
@@ -118,7 +123,7 @@ bool of_mdiobus_child_is_phy(struct device_node *child)
 	if (of_get_phy_id(child, &phy_id) != -EINVAL)
 		return true;
 
-	if (of_device_is_compatible(child, "ethernet-phy-ieee802.3-c45"))
+	if (of_mdiobus_child_is_c45_phy(child))
 		return true;
 
 	if (of_device_is_compatible(child, "ethernet-phy-ieee802.3-c22"))
@@ -138,6 +143,32 @@ bool of_mdiobus_child_is_phy(struct device_node *child)
 }
 EXPORT_SYMBOL(of_mdiobus_child_is_phy);
 
+static int of_mdiobus_register_child(struct mii_bus *mdio,
+				     struct device_node *child, bool *scanphys)
+{
+	int addr, rc;
+
+	addr = of_mdio_parse_addr(&mdio->dev, child);
+	if (addr < 0) {
+		*scanphys = true;
+		return 0;
+	}
+
+	if (mdiobus_is_registered_device(mdio, addr))
+		return 0;
+
+	if (of_mdiobus_child_is_phy(child))
+		rc = of_mdiobus_register_phy(mdio, child, addr);
+	else
+		rc = of_mdiobus_register_device(mdio, child, addr);
+
+	if (rc == -ENODEV)
+		dev_err(&mdio->dev, "MDIO device at address %d is missing.\n",
+			addr);
+
+	return rc;
+}
+
 /**
  * __of_mdiobus_register - Register mii_bus and create PHYs from the device tree
  * @mdio: pointer to mii_bus structure
@@ -178,24 +209,26 @@ int __of_mdiobus_register(struct mii_bus *mdio, struct device_node *np,
 	if (rc)
 		return rc;
 
-	/* Loop over the child nodes and register a phy_device for each phy */
+	/* Loop over the child nodes, skipping C45 PHYs so we can scan for
+	 * broken C22 PHYs. The C45 PHYs will be registered afterwards.
+	 */
 	for_each_available_child_of_node(np, child) {
-		addr = of_mdio_parse_addr(&mdio->dev, child);
-		if (addr < 0) {
-			scanphys = true;
+		if (of_mdiobus_child_is_c45_phy(child))
 			continue;
-		}
+		rc = of_mdiobus_register_child(mdio, child, &scanphys);
+		if (rc)
+			goto unregister;
+	}
 
-		if (of_mdiobus_child_is_phy(child))
-			rc = of_mdiobus_register_phy(mdio, child, addr);
-		else
-			rc = of_mdiobus_register_device(mdio, child, addr);
+	/* Some C22 PHYs are broken with C45 transactions. */
+	mdiobus_scan_for_broken_c45_access(mdio);
 
-		if (rc == -ENODEV)
-			dev_err(&mdio->dev,
-				"MDIO device at address %d is missing.\n",
-				addr);
-		else if (rc)
+	/* Now add any missing C45 PHYs. If C45 access is not allowed, they
+	 * will be registered with C45-over-C22 access.
+	 */
+	for_each_available_child_of_node(np, child) {
+		rc = of_mdiobus_register_child(mdio, child, &scanphys);
+		if (rc)
 			goto unregister;
 	}
 

-- 
2.39.2