[PATCH net-next v11 06/10] net: mdio: realtek-rtl9300: Configure hardware polling during probing

[Markus Stockhausen <markus.stockhausen@gmx.de>]

During PHY probing and configuration complex configuration sequences
might be issued and firmware might be loaded. Hardware polling can
interfere badly with that. E.g. a hardware polling MMD c45 over c22
request might break an ongoing firmware loading sequence.

To avoid such issues the polling of the Realtek Otto switches can be
(de)activated with one or two 32 bit mask registers. Each bit enables
(=1) or disables (=0) the polling of the corresponding port. Make use
of this as follows:

- Disable polling for all ports when the MDIO driver starts.
- Reenable polling just after the PHY has been attached.
- Disable polling just before the PHY is being detached.

This synchronizes the kernel and hardware polling to some extent. It
gracefully handles deferred probing of PHYs in case the driver is
loaded asynchronously during boot. Additionally it brings the hardware
polling into a consistent operation mode for devices where U-Boot does
not take care.

Important notes about the implementation:

Realtek is very inconsistent about its register naming. RTL930x uses
SMI_POLL_CTRL for polling control while it is SMI_PORT_POLLING_CTRL
on RTL931x. Keep these vendor names.

These devices do not support power management for the whole system.
So mdio_bus_phy_resume() is not used and it is not required to
disable/enable hardware polling for that usecase.

[1] https://github.com/openwrt/openwrt/blob/main/target/linux/realtek/files-6.18/drivers/net/mdio/mdio-realtek-otto.c#L818
[2] https://lore.kernel.org/netdev/680696024a8648535ce6dee771fe4de67802e0e8.1769053496.git.daniel@makrotopia.org/

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
---
 drivers/net/mdio/mdio-realtek-rtl9300.c | 62 +++++++++++++++++++++++++
 1 file changed, 62 insertions(+)

diff --git a/drivers/net/mdio/mdio-realtek-rtl9300.c b/drivers/net/mdio/mdio-realtek-rtl9300.c
index 1873928b362d..161df1818d02 100644
--- a/drivers/net/mdio/mdio-realtek-rtl9300.c
+++ b/drivers/net/mdio/mdio-realtek-rtl9300.c
@@ -145,6 +145,7 @@
 #define   RTL9300_PHY_CTRL_INDATA		GENMASK(31, 16)
 #define   RTL9300_PHY_CTRL_DATA			GENMASK(15, 0)
 #define RTL9300_SMI_ACCESS_PHY_CTRL_3		0xcb7c
+#define RTL9300_SMI_POLL_CTRL			0xca90
 #define RTL9300_SMI_PORT0_5_ADDR_CTRL		0xcb80
 
 #define RTL9310_NUM_BUSES			4
@@ -170,6 +171,7 @@
 #define   RTL9310_PHY_CTRL_INDATA		GENMASK(15, 0)
 #define RTL9310_SMI_INDRT_ACCESS_MMD_CTRL	0x0c18
 #define RTL9310_SMI_PORT_ADDR_CTRL		0x0c74
+#define RTL9310_SMI_PORT_POLLING_CTRL		0x0ccc
 #define RTL9310_SMI_PORT_POLLING_SEL		0x0c9c
 
 #define PHY_CTRL_CMD				BIT(0)
@@ -217,6 +219,7 @@ struct otto_emdio_info {
 	u8 num_buses;
 	u8 num_ports;
 	u16 num_pages;
+	u32 poll_ctrl;
 	int (*setup_controller)(struct otto_emdio_priv *priv);
 	int (*read_c22)(struct mii_bus *bus, int port, int regnum, u32 *value);
 	int (*read_c45)(struct mii_bus *bus, int port, int dev_addr, int regnum, u32 *value);
@@ -252,6 +255,12 @@ static struct otto_emdio_priv *otto_emdio_bus_to_priv(struct mii_bus *bus)
 	return chan->priv;
 }
 
+static int otto_emdio_set_port_polling(struct otto_emdio_priv *priv, int port, bool active)
+{
+	return regmap_assign_bits(priv->regmap, priv->info->poll_ctrl + (port / 32) * 4,
+				  BIT(port % 32), active);
+}
+
 static int otto_emdio_run_cmd(struct mii_bus *bus, u32 cmd,
 			      struct otto_emdio_cmd_regs *cmd_data)
 {
@@ -582,6 +591,37 @@ static int otto_emdio_9310_setup_controller(struct otto_emdio_priv *priv)
 	return 0;
 }
 
+static int otto_emdio_notify_phy_attach(struct phy_device *phydev)
+{
+	struct otto_emdio_priv *priv = otto_emdio_bus_to_priv(phydev->mdio.bus);
+	int port = otto_emdio_phy_to_port(phydev->mdio.bus, phydev->mdio.addr);
+
+	if (port < 0)
+		return port;
+
+	return otto_emdio_set_port_polling(priv, port, true);
+}
+
+static void otto_emdio_notify_phy_detach(struct phy_device *phydev)
+{
+	struct mii_bus *bus = phydev->mdio.bus;
+	struct otto_emdio_priv *priv;
+	int port;
+
+	/* controller->priv might might have been freed before during teardown */
+	if (bus->state != MDIOBUS_REGISTERED)
+		return;
+
+	priv = otto_emdio_bus_to_priv(phydev->mdio.bus);
+	port = otto_emdio_phy_to_port(phydev->mdio.bus, phydev->mdio.addr);
+
+	if (port < 0)
+		return;
+
+	if (otto_emdio_set_port_polling(priv, port, false))
+		dev_err(bus->parent, "failed to disable polling for port %d\n", port);
+}
+
 static int otto_emdio_probe_one(struct device *dev, struct otto_emdio_priv *priv,
 				 struct fwnode_handle *node)
 {
@@ -611,6 +651,9 @@ static int otto_emdio_probe_one(struct device *dev, struct otto_emdio_priv *priv
 		bus->write = otto_emdio_write_c22;
 	}
 	bus->parent = dev;
+	bus->notify_phy_attach = otto_emdio_notify_phy_attach;
+	bus->notify_phy_detach = otto_emdio_notify_phy_detach;
+
 	chan = bus->priv;
 	chan->mdio_bus = mdio_bus;
 	chan->priv = priv;
@@ -727,6 +770,19 @@ static int otto_emdio_map_ports(struct device *dev)
 	return err;
 }
 
+static int otto_emdio_init_polling(struct otto_emdio_priv *priv)
+{
+	int err;
+
+	for (int port = 0; port < priv->info->num_ports; port++) {
+		err = otto_emdio_set_port_polling(priv, port, false);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
 static int otto_emdio_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -746,6 +802,10 @@ static int otto_emdio_probe(struct platform_device *pdev)
 	if (IS_ERR(priv->regmap))
 		return PTR_ERR(priv->regmap);
 
+	err = otto_emdio_init_polling(priv);
+	if (err)
+		return err;
+
 	platform_set_drvdata(pdev, priv);
 
 	err = otto_emdio_map_ports(dev);
@@ -786,6 +846,7 @@ static const struct otto_emdio_info otto_emdio_9300_info = {
 	.num_buses = RTL9300_NUM_BUSES,
 	.num_ports = RTL9300_NUM_PORTS,
 	.num_pages = RTL9300_NUM_PAGES,
+	.poll_ctrl = RTL9300_SMI_POLL_CTRL,
 	.setup_controller = otto_emdio_9300_setup_controller,
 	.read_c22 = otto_emdio_9300_read_c22,
 	.read_c45 = otto_emdio_9300_read_c45,
@@ -811,6 +872,7 @@ static const struct otto_emdio_info otto_emdio_9310_info = {
 	.num_buses = RTL9310_NUM_BUSES,
 	.num_pages = RTL9310_NUM_PAGES,
 	.num_ports = RTL9310_NUM_PORTS,
+	.poll_ctrl = RTL9310_SMI_PORT_POLLING_CTRL,
 	.setup_controller = otto_emdio_9310_setup_controller,
 	.read_c22 = otto_emdio_9310_read_c22,
 	.read_c45 = otto_emdio_9310_read_c45,
-- 
2.55.0