Currently the MII clk vs. data delay is configured based on the PHY
interface mode.

In addition to that add support for setting up MII delays using the
standard Device Tree properties 'tx-internal-delay-ps' and
'rx-internal-delay-ps' and only fall back to using the PHY interface
mode in case both properties are unused.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
 drivers/net/dsa/lantiq/lantiq_gswip.h        |  4 +++
 drivers/net/dsa/lantiq/lantiq_gswip_common.c | 31 ++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/drivers/net/dsa/lantiq/lantiq_gswip.h b/drivers/net/dsa/lantiq/lantiq_gswip.h
index 42000954d842..0c32ec85e127 100644
--- a/drivers/net/dsa/lantiq/lantiq_gswip.h
+++ b/drivers/net/dsa/lantiq/lantiq_gswip.h
@@ -82,6 +82,10 @@
 #define GSWIP_MII_PCDU5			0x05
 #define  GSWIP_MII_PCDU_TXDLY_MASK	GENMASK(2, 0)
 #define  GSWIP_MII_PCDU_RXDLY_MASK	GENMASK(9, 7)
+#define  GSWIP_MII_PCDU_TXDLY(x)	u16_encode_bits(((x) / 500), GSWIP_MII_PCDU_TXDLY_MASK)
+#define  GSWIP_MII_PCDU_RXDLY(x)	u16_encode_bits(((x) / 500), GSWIP_MII_PCDU_RXDLY_MASK)
+#define GSWIP_MII_PCDU_RXDLY_DEFAULT	2000 /* picoseconds */
+#define GSWIP_MII_PCDU_TXDLY_DEFAULT	2000 /* picoseconds */
 
 /* GSWIP Core Registers */
 #define GSWIP_SWRES			0x000
diff --git a/drivers/net/dsa/lantiq/lantiq_gswip_common.c b/drivers/net/dsa/lantiq/lantiq_gswip_common.c
index 94b187899db6..60a83093cd10 100644
--- a/drivers/net/dsa/lantiq/lantiq_gswip_common.c
+++ b/drivers/net/dsa/lantiq/lantiq_gswip_common.c
@@ -622,6 +622,34 @@ static int gswip_port_vlan_filtering(struct dsa_switch *ds, int port,
 	return 0;
 }
 
+static bool gswip_mii_delay_setup(struct gswip_priv *priv, struct dsa_port *dp)
+{
+	u32 tx_delay = GSWIP_MII_PCDU_TXDLY_DEFAULT;
+	u32 rx_delay = GSWIP_MII_PCDU_RXDLY_DEFAULT;
+	struct device_node *port_dn = dp->dn;
+	bool used;
+	int ret;
+
+	ret = of_property_read_u32(port_dn, "tx-internal-delay-ps", &tx_delay);
+	if (ret && ret != -EINVAL)
+		return ret;
+	used = !ret;
+
+	ret = of_property_read_u32(port_dn, "rx-internal-delay-ps", &rx_delay);
+	if (ret && ret != -EINVAL)
+		return ret;
+	used |= !ret;
+
+	if (used)
+		gswip_mii_mask_pcdu(priv, GSWIP_MII_PCDU_TXDLY_MASK |
+					  GSWIP_MII_PCDU_RXDLY_MASK,
+					  GSWIP_MII_PCDU_TXDLY(tx_delay) |
+					  GSWIP_MII_PCDU_RXDLY(rx_delay),
+					  dp->index);
+
+	return used;
+}
+
 static int gswip_setup(struct dsa_switch *ds)
 {
 	unsigned int cpu_ports = dsa_cpu_ports(ds);
@@ -1419,6 +1447,9 @@ static void gswip_phylink_mac_config(struct phylink_config *config,
 			   GSWIP_MII_CFG_RGMII_IBS | GSWIP_MII_CFG_LDCLKDIS,
 			   miicfg, port);
 
+	if (gswip_mii_delay_setup(priv, dp))
+		return;
+
 	switch (state->interface) {
 	case PHY_INTERFACE_MODE_RGMII_ID:
 		gswip_mii_mask_pcdu(priv, GSWIP_MII_PCDU_TXDLY_MASK |
-- 
2.51.0