Microchip KSZ8863/KSZ8873 have the ability to select between internal
and external RMII reference clock. By default, reference clock
needs to be provided via REFCLKI_3 pin. If required, device can be
setup to provide RMII clock internally so that REFCLKI_3 pin can be
left unconnected.
Add a new "microchip,rmii-clk-internal" property which will set
RMII clock reference to internal. If property is not set, reference
clock needs to be provided externally.

While at it, move the ksz8795_cpu_interface_select() to
ksz8_config_cpu_port() to get a cleaner call path for cpu port.

Signed-off-by: Ante Knezic <ante.knezic@helmholz.de>
---
 drivers/net/dsa/microchip/ksz8795.c     | 56 +++++++++++++++++++++++++++++----
 drivers/net/dsa/microchip/ksz8795_reg.h |  3 ++
 2 files changed, 53 insertions(+), 6 deletions(-)

diff --git a/drivers/net/dsa/microchip/ksz8795.c b/drivers/net/dsa/microchip/ksz8795.c
index 4bf4d67557dc..a749a4a970ec 100644
--- a/drivers/net/dsa/microchip/ksz8795.c
+++ b/drivers/net/dsa/microchip/ksz8795.c
@@ -1358,6 +1358,9 @@ static void ksz8795_cpu_interface_select(struct ksz_device *dev, int port)
 {
 	struct ksz_port *p = &dev->ports[port];
 
+	if (!ksz_is_ksz87xx(dev))
+		return;
+
 	if (!p->interface && dev->compat_interface) {
 		dev_warn(dev->dev,
 			 "Using legacy switch \"phy-mode\" property, because it is missing on port %d node. "
@@ -1391,18 +1394,55 @@ void ksz8_port_setup(struct ksz_device *dev, int port, bool cpu_port)
 	/* enable 802.1p priority */
 	ksz_port_cfg(dev, port, P_PRIO_CTRL, PORT_802_1P_ENABLE, true);
 
-	if (cpu_port) {
-		if (!ksz_is_ksz88x3(dev))
-			ksz8795_cpu_interface_select(dev, port);
-
+	if (cpu_port)
 		member = dsa_user_ports(ds);
-	} else {
+	else
 		member = BIT(dsa_upstream_port(ds, port));
-	}
 
 	ksz8_cfg_port_member(dev, port, member);
 }
 
+static int ksz88x3_config_rmii_clk(struct ksz_device *dev, int cpu_port)
+{
+	struct device_node *ports, *port, *cpu_node;
+	bool rmii_clk_internal;
+
+	if (!ksz_is_ksz88x3(dev))
+		return 0;
+
+	cpu_node = NULL;
+
+	ports = of_get_child_by_name(dev->dev->of_node, "ports");
+	if (!ports)
+		ports = of_get_child_by_name(dev->dev->of_node,
+					     "ethernet-ports");
+	if (!ports)
+		return -ENODEV;
+
+	for_each_available_child_of_node(ports, port) {
+		u32 index;
+
+		if (of_property_read_u32(port, "reg", &index) < 0)
+			return -ENODEV;
+
+		if (index == cpu_port) {
+			cpu_node = port;
+			break;
+		}
+	}
+
+	if (!cpu_node)
+		return -ENODEV;
+
+	rmii_clk_internal = of_property_read_bool(cpu_node,
+						  "microchip,rmii-clk-internal");
+
+	ksz_cfg(dev, KSZ88X3_REG_FVID_AND_HOST_MODE,
+		KSZ88X3_PORT3_RMII_CLK_INTERNAL, rmii_clk_internal);
+
+	return 0;
+}
+
 void ksz8_config_cpu_port(struct dsa_switch *ds)
 {
 	struct ksz_device *dev = ds->priv;
@@ -1419,6 +1459,10 @@ void ksz8_config_cpu_port(struct dsa_switch *ds)
 
 	ksz8_port_setup(dev, dev->cpu_port, true);
 
+	ksz8795_cpu_interface_select(dev, dev->cpu_port);
+	if (ksz88x3_config_rmii_clk(dev, dev->cpu_port))
+		dev_err(dev->dev, "Failed to set rmii reference clock source mode");
+
 	for (i = 0; i < dev->phy_port_cnt; i++) {
 		ksz_port_stp_state_set(ds, i, BR_STATE_DISABLED);
 	}
diff --git a/drivers/net/dsa/microchip/ksz8795_reg.h b/drivers/net/dsa/microchip/ksz8795_reg.h
index 3c9dae53e4d8..beca974e0171 100644
--- a/drivers/net/dsa/microchip/ksz8795_reg.h
+++ b/drivers/net/dsa/microchip/ksz8795_reg.h
@@ -22,6 +22,9 @@
 #define KSZ8863_GLOBAL_SOFTWARE_RESET	BIT(4)
 #define KSZ8863_PCS_RESET		BIT(0)
 
+#define KSZ88X3_REG_FVID_AND_HOST_MODE  0xC6
+#define KSZ88X3_PORT3_RMII_CLK_INTERNAL BIT(3)
+
 #define REG_SW_CTRL_0			0x02
 
 #define SW_NEW_BACKOFF			BIT(7)
-- 
2.11.0

On Fri, Nov 24, 2023 at 05:01:48PM +0100, Ante Knezic wrote:
> +static int ksz88x3_config_rmii_clk(struct ksz_device *dev, int cpu_port)
> +{
> +	struct device_node *ports, *port, *cpu_node;
> +	bool rmii_clk_internal;
> +
> +	if (!ksz_is_ksz88x3(dev))
> +		return 0;
> +
> +	cpu_node = NULL;
> +
> +	ports = of_get_child_by_name(dev->dev->of_node, "ports");
> +	if (!ports)
> +		ports = of_get_child_by_name(dev->dev->of_node,
> +					     "ethernet-ports");
> +	if (!ports)
> +		return -ENODEV;
> +
> +	for_each_available_child_of_node(ports, port) {
> +		u32 index;
> +
> +		if (of_property_read_u32(port, "reg", &index) < 0)
> +			return -ENODEV;
> +
> +		if (index == cpu_port) {
> +			cpu_node = port;
> +			break;
> +		}
> +	}
> +
> +	if (!cpu_node)
> +		return -ENODEV;

Too much code. Assuming you have struct dsa_port *cpu_dp, you can access
cpu_dp->dn instead of re-parsing the device tree.

> +
> +	rmii_clk_internal = of_property_read_bool(cpu_node,
> +						  "microchip,rmii-clk-internal");
> +
> +	ksz_cfg(dev, KSZ88X3_REG_FVID_AND_HOST_MODE,
> +		KSZ88X3_PORT3_RMII_CLK_INTERNAL, rmii_clk_internal);
> +
> +	return 0;
> +}

Please wait for 24 hours before reposting, maybe you get more feedback.