[PATCH v3 4/7] net: dsa: mediatek: support PLL setup on MMIO MT7530

[Caleb James DeLisle <cjd@cjdns.fr>]

On MT7530 and MT7531, PHYs are an integral part of the switch. However,
on MT7530, certain configuration such as PLL setup is done via special
registers on one of the PHYs.

In an MMIO implementation, the MDIO bus is part of the switch itself.
This bus is already setup for PHY calibration so begin using it for
core switch PLL setup.

Signed-off-by: Caleb James DeLisle <cjd@cjdns.fr>
---
 drivers/net/dsa/mt7530.c | 15 +++++++++++++++
 drivers/net/dsa/mt7530.h |  4 ++++
 2 files changed, 19 insertions(+)

diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
index 3eb2e11d6985..d09ff207e2df 100644
--- a/drivers/net/dsa/mt7530.c
+++ b/drivers/net/dsa/mt7530.c
@@ -77,6 +77,12 @@ core_write(struct mt7530_priv *priv, u32 reg, u32 val)
 	struct mii_bus *bus = priv->bus;
 	int ret;
 
+	if (!bus)
+		bus = priv->child_bus;
+
+	if (WARN_ON_ONCE(!bus))
+		return;
+
 	mt7530_mutex_lock(priv);
 
 	/* Write the desired MMD Devad */
@@ -112,6 +118,12 @@ core_rmw(struct mt7530_priv *priv, u32 reg, u32 mask, u32 set)
 	u32 val;
 	int ret;
 
+	if (!bus)
+		bus = priv->child_bus;
+
+	if (WARN_ON_ONCE(!bus))
+		return;
+
 	mt7530_mutex_lock(priv);
 
 	/* Write the desired MMD Devad */
@@ -2472,8 +2484,11 @@ mt7530_setup_mdio(struct mt7530_priv *priv)
 	if (priv->irq_domain && !mnp)
 		mt7530_setup_mdio_irq(priv);
 
+	priv->child_bus = bus;
+
 	ret = devm_of_mdiobus_register(dev, bus, mnp);
 	if (ret) {
+		priv->child_bus = NULL;
 		dev_err(dev, "failed to register MDIO bus: %d\n", ret);
 		if (priv->irq_domain && !mnp)
 			mt7530_free_mdio_irq(priv);
diff --git a/drivers/net/dsa/mt7530.h b/drivers/net/dsa/mt7530.h
index 108c831dd012..5b7394f6383c 100644
--- a/drivers/net/dsa/mt7530.h
+++ b/drivers/net/dsa/mt7530.h
@@ -886,6 +886,9 @@ struct mt753x_info {
  * @dev:		The device pointer
  * @ds:			The pointer to the dsa core structure
  * @bus:		The bus used for the device and built-in PHY
+ * @child_bus:		The bus created by the device, on MDIO implementations
+ *			this is bus indirectly accesses `bus`, on MMIO
+ *			implementations this bus is part of the switch.
  * @regmap:		The regmap instance representing all switch registers
  * @rstc:		The pointer to reset control used by MCM
  * @core_pwr:		The power supplied into the core
@@ -914,6 +917,7 @@ struct mt7530_priv {
 	struct device		*dev;
 	struct dsa_switch	*ds;
 	struct mii_bus		*bus;
+	struct mii_bus		*child_bus;
 	struct regmap		*regmap;
 	struct reset_control	*rstc;
 	struct regulator	*core_pwr;
-- 
2.39.5