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From:   Heiko Stuebner <heiko@sntech.de>
To:     andrew@lunn.ch, hkallweit1@gmail.com
Cc:     linux@armlinux.org.uk, davem@davemloft.net, edumazet@google.com,
        kuba@kernel.org, pabeni@redhat.com, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, quentin.schulz@theobroma-systems.com,
        heiko@sntech.de, Heiko Stuebner <heiko.stuebner@cherry.de>
Subject: [PATCH] net: mdio: enable optional clock when registering a phy from devicetree
Date:   Fri,  1 Dec 2023 15:24:53 +0100
Message-Id: <20231201142453.324697-1-heiko@sntech.de>
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From: Heiko Stuebner <heiko.stuebner@cherry.de>

The ethernet-phy binding (now) specifys that phys can declare a clock
supply. Phy driver itself will handle this when probing the phy-driver.

But there is a gap when trying to detect phys, because the mdio-bus needs
to talk to the phy to get its phy-id. Using actual phy-ids in the dt like
       compatible = "ethernet-phy-id0022.1640",
                    "ethernet-phy-ieee802.3-c22";
of course circumvents this, but in turn hard-codes the phy.

With boards often having multiple phy options and the mdio-bus being able
to actually probe devices, this feels like a step back.

So check for the existence of a phy-clock per the -dtbinding in the
of_mdiobus_register_phy() and enable the clock around the
fwnode_mdiobus_register_phy() call which tries to determine the phy-id.

Signed-off-by: Heiko Stuebner <heiko.stuebner@cherry.de>
---
 drivers/net/mdio/of_mdio.c | 34 +++++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/drivers/net/mdio/of_mdio.c b/drivers/net/mdio/of_mdio.c
index 64ebcb6d235c..895b12849b23 100644
--- a/drivers/net/mdio/of_mdio.c
+++ b/drivers/net/mdio/of_mdio.c
@@ -8,6 +8,7 @@
  * out of the OpenFirmware device tree and using it to populate an mii_bus.
  */
 
+#include <linux/clk.h>
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/fwnode_mdio.h>
@@ -15,6 +16,7 @@
 #include <linux/module.h>
 #include <linux/netdevice.h>
 #include <linux/of.h>
+#include <linux/of_clk.h>
 #include <linux/of_irq.h>
 #include <linux/of_mdio.h>
 #include <linux/of_net.h>
@@ -46,7 +48,37 @@ EXPORT_SYMBOL(of_mdiobus_phy_device_register);
 static int of_mdiobus_register_phy(struct mii_bus *mdio,
 				    struct device_node *child, u32 addr)
 {
-	return fwnode_mdiobus_register_phy(mdio, of_fwnode_handle(child), addr);
+	struct clk *clk = NULL;
+	int ret;
+
+	/* ethernet-phy binding specifies a maximum of 1 clock */
+	if (of_clk_get_parent_count(child) == 1) {
+		clk = of_clk_get(child, 0);
+		if (IS_ERR(clk)) {
+			if (PTR_ERR(clk) != -ENOENT)
+				return dev_err_probe(&mdio->dev, PTR_ERR(clk),
+						     "Could not get defined clock for MDIO device at address %u\n",
+						     addr);
+
+			clk = NULL;
+		}
+	}
+
+	ret = clk_prepare_enable(clk);
+	if (ret < 0) {
+		clk_put(clk);
+		dev_err(&mdio->dev,
+			"Could not enable clock for MDIO device at address %u: %d\n",
+			addr, ret);
+		return ret;
+	}
+
+	ret = fwnode_mdiobus_register_phy(mdio, of_fwnode_handle(child), addr);
+
+	clk_disable_unprepare(clk);
+	clk_put(clk);
+
+	return ret;
 }
 
 static int of_mdiobus_register_device(struct mii_bus *mdio,
-- 
2.39.2