net: pcs: lynxi: implement pcs_disable op

When switching from 10GBase-R/5GBase-R/USXGMII to one of the interface
modes provided by mtk-pcs-lynxi we need to make sure to always perform
a full configuration of the PHYA.

Implement pcs_disable op which resets the stored interface mode to
PHY_INTERFACE_MODE_NA to trigger a full reconfiguration once the LynxI
PCS driver had previously been deselected in favor of another PCS
driver such as the to-be-added driver for the USXGMII PCS found in
MT7988.
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Link: https://lore.kernel.org/r/f23d1a60d2c9d2fb72e32dcb0eaa5f7e867a3d68.1692327891.git.daniel@makrotopia.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/pcs/pcs-mtk-lynxi.c

@@ -233,11 +233,19 @@ static void mtk_pcs_lynxi_link_up(struct phylink_pcs *pcs,
 	}
 }
 
+static void mtk_pcs_lynxi_disable(struct phylink_pcs *pcs)
+{
+	struct mtk_pcs_lynxi *mpcs = pcs_to_mtk_pcs_lynxi(pcs);
+
+	mpcs->interface = PHY_INTERFACE_MODE_NA;
+}
+
 static const struct phylink_pcs_ops mtk_pcs_lynxi_ops = {
 	.pcs_get_state = mtk_pcs_lynxi_get_state,
 	.pcs_config = mtk_pcs_lynxi_config,
 	.pcs_an_restart = mtk_pcs_lynxi_restart_an,
 	.pcs_link_up = mtk_pcs_lynxi_link_up,
+	.pcs_disable = mtk_pcs_lynxi_disable,
 };
 
 struct phylink_pcs *mtk_pcs_lynxi_create(struct device *dev,