[PATCH RFC net-next 5/5] net: stmmac: fix resume when media is in low-power mode

["Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>]

The Synopsys Designwavre GMAC core databook requires all clocks to be
active in order to complete software reset.

This means if the PHY receive clock has been stopped due to the media
being in EEE low-power state, and the PHY being permitted to stop its
clock, then software reset will not complete.

Phylink now provides a way to work around this by calling
phylink_prepare_resume() before attempting to issue a reset. This will
prepare any attached PHY by disabling its permission to stop the clock.
phylink_resume() will restore the receive clock stop setting according
to the configuration passed from the netdev driver.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 23c610f7c779..13796b1c8d7c 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -7925,6 +7925,8 @@ int stmmac_resume(struct device *dev)
 	}
 
 	rtnl_lock();
+	phylink_prepare_resume(priv->phylink);
+
 	mutex_lock(&priv->lock);
 
 	stmmac_reset_queues_param(priv);
-- 
2.30.2