[PATCH net] net: dsa: lantiq_gswip: Let GSWIP automatically set the xMII clock

[Martin Blumenstingl]

The xMII interface clock depends on the PHY interface (MII, RMII, RGMII)
as well as the current link speed. Explicitly configure the GSWIP to
automatically select the appropriate xMII interface clock.

This fixes an issue seen by some users where ports using an external
RMII or RGMII PHY were deaf (no RX or TX traffic could be seen). Most
likely this is due to an "invalid" xMII clock being selected either by
the bootloader or hardware-defaults.

Fixes: 14fceff4771e51 ("net: dsa: Add Lantiq / Intel DSA driver for vrx200")
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
---
It would be great to have this fix backported to Linux 5.4 and 5.10 to
get rid of one more blocker which prevents OpenWrt from switching to
this new in-tree driver.


 drivers/net/dsa/lantiq_gswip.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/dsa/lantiq_gswip.c b/drivers/net/dsa/lantiq_gswip.c
index 52e865a3912c..809dfa3be6bb 100644
--- a/drivers/net/dsa/lantiq_gswip.c
+++ b/drivers/net/dsa/lantiq_gswip.c
@@ -799,10 +799,15 @@ static int gswip_setup(struct dsa_switch *ds)
 	/* Configure the MDIO Clock 2.5 MHz */
 	gswip_mdio_mask(priv, 0xff, 0x09, GSWIP_MDIO_MDC_CFG1);
 
-	/* Disable the xMII link */
-	for (i = 0; i < priv->hw_info->max_ports; i++)
+	for (i = 0; i < priv->hw_info->max_ports; i++) {
+		/* Disable the xMII link */
 		gswip_mii_mask_cfg(priv, GSWIP_MII_CFG_EN, 0, i);
 
+		/* Automatically select the xMII interface clock */
+		gswip_mii_mask_cfg(priv, GSWIP_MII_CFG_RATE_MASK,
+				   GSWIP_MII_CFG_RATE_AUTO, i);
+	}
+
 	/* enable special tag insertion on cpu port */
 	gswip_switch_mask(priv, 0, GSWIP_FDMA_PCTRL_STEN,
 			  GSWIP_FDMA_PCTRLp(cpu_port));
-- 
2.31.0