[PATCH net-next v15 6/9] net: stmmac: qcom-ethqos: update phy_mode to the resolved interface in mac_finish()

[Bartosz Golaszewski]

ethqos->phy_mode is read by serdes_powerup() and
qcom_ethqos_set_sgmii_loopback() to configure the SerDes and its
wrapper for the correct interface. It is set once at probe from the DT
phy-mode property and never updated.

phylink resolves the actual runtime interface and passes it to the
mac_finish() callback. On platforms that only ever operate at one speed
these two values are always the same, but when the interface changes
at runtime - for example switching between SGMII and 2500BASE-X - the
stored value becomes stale. The next serdes_powerup() call, on
a subsequent link cycle, then reinitializes the SerDes to the wrong mode.

Update ethqos->phy_mode from the interface argument in
ethqos_mac_finish_serdes() so that it always reflects the last
resolved interface.

With that, we now update the phy_mode to the runtime-resolved interface,
so any subsequent resume with a 1G SGMII link skips the loopback setup
and the DMA reset hangs. To remedy this, extend the guard to include
PHY_INTERFACE_MODE_SGMII.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski at oss.qualcomm.com>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c
index 47b70b5e706f221c01f1c0ae3b1acafae6641165..e067ceee016217c49d3b3d572fd9f33e562d1a75 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c
@@ -190,7 +190,8 @@ static void
 qcom_ethqos_set_sgmii_loopback(struct qcom_ethqos *ethqos, bool enable)
 {
 	if (!ethqos->needs_sgmii_loopback ||
-	    ethqos->phy_mode != PHY_INTERFACE_MODE_2500BASEX)
+	    (ethqos->phy_mode != PHY_INTERFACE_MODE_2500BASEX &&
+	     ethqos->phy_mode != PHY_INTERFACE_MODE_SGMII))
 		return;
 
 	rgmii_updatel(ethqos,
@@ -634,6 +635,12 @@ static int ethqos_mac_finish_serdes(struct net_device *ndev, void *priv,
 
 	qcom_ethqos_set_sgmii_loopback(ethqos, false);
 
+	/* The interface mode is only known once phylink has resolved it and
+	 * may change at runtime, so keep it in sync for later
+	 * serdes_powerup()/serdes_powerdown() calls.
+	 */
+	ethqos->phy_mode = interface;
+
 	if (interface == PHY_INTERFACE_MODE_SGMII ||
 	    interface == PHY_INTERFACE_MODE_2500BASEX)
 		ret = phy_set_mode_ext(ethqos->serdes_phy, PHY_MODE_ETHERNET,

-- 
2.47.3