[PATCH net-next v2 5/7] net: stmmac: Signal to PHY/PCS drivers to keep RX clock on

[Romain Gantois <romain.gantois@bootlin.com>]

There is a reocurring issue with stmmac controllers where the MAC fails to
initialize its hardware if an RX clock signal isn't provided on the MAC/PHY
link.

This causes issues when PHY or PCS devices either go into suspend while
cutting the RX clock or do not bring the clock signal up early enough for
the MAC to initialize successfully.

Set the mac_requires_rxc flag in the stmmac phylink config so that PHY/PCS
drivers know to keep the RX clock up at all times.

Reported-by: Clark Wang <xiaoning.wang@nxp.com>
Link: https://lore.kernel.org/all/20230202081559.3553637-1-xiaoning.wang@nxp.com/
Reported-by: Clément Léger <clement.leger@bootlin.com>
Link: https://lore.kernel.org/linux-arm-kernel/20230116103926.276869-4-clement.leger@bootlin.com/
Suggested-by: Russell King <linux@armlinux.org.uk>
Signed-off-by: Romain Gantois <romain.gantois@bootlin.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 72e02ef0ee6b..7345e3fa07c4 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -1218,6 +1218,9 @@ static int stmmac_phy_setup(struct stmmac_priv *priv)
 	priv->phylink_config.type = PHYLINK_NETDEV;
 	priv->phylink_config.mac_managed_pm = true;
 
+	/* Stmmac always requires an RX clock for hardware initialization */
+	priv->phylink_config.mac_requires_rxc = true;
+
 	mdio_bus_data = priv->plat->mdio_bus_data;
 	if (mdio_bus_data)
 		priv->phylink_config.ovr_an_inband =
@@ -3402,6 +3405,10 @@ static int stmmac_hw_setup(struct net_device *dev, bool ptp_register)
 	u32 chan;
 	int ret;
 
+	/* Make sure RX clock is enabled */
+	if (priv->hw->phylink_pcs)
+		phylink_pcs_pre_init(priv->phylink, priv->hw->phylink_pcs);
+
 	/* DMA initialization and SW reset */
 	ret = stmmac_init_dma_engine(priv);
 	if (ret < 0) {

-- 
2.43.0