[PATCH 4.8 29/49] net: stmmac: Fix lack of link transition for fixed PHYs

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Florian Fainelli <f.fainelli@gmail.com>


[ Upstream commit c51e424dc79e1428afc4d697cdb6a07f7af70cbf ]

Commit 52f95bbfcf72 ("stmmac: fix adjust link call in case of a switch
is attached") added some logic to avoid polling the fixed PHY and
therefore invoking the adjust_link callback more than once, since this
is a fixed PHY and link events won't be generated.

This works fine the first time, because we start with phydev->irq =
PHY_POLL, so we call adjust_link, then we set phydev->irq =
PHY_IGNORE_INTERRUPT and we stop polling the PHY.

Now, if we called ndo_close(), which calls both phy_stop() and does an
explicit netif_carrier_off(), we end up with a link down. Upon calling
ndo_open() again, despite starting the PHY state machine, we have
PHY_IGNORE_INTERRUPT set, and we generate no link event at all, so the
link is permanently down.

Fixes: 52f95bbfcf72 ("stmmac: fix adjust link call in case of a switch is attached")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -871,6 +871,13 @@ static int stmmac_init_phy(struct net_de
 		return -ENODEV;
 	}
 
+	/* stmmac_adjust_link will change this to PHY_IGNORE_INTERRUPT to avoid
+	 * subsequent PHY polling, make sure we force a link transition if
+	 * we have a UP/DOWN/UP transition
+	 */
+	if (phydev->is_pseudo_fixed_link)
+		phydev->irq = PHY_POLL;
+
 	pr_debug("stmmac_init_phy:  %s: attached to PHY (UID 0x%x)"
 		 " Link = %d\n", dev->name, phydev->phy_id, phydev->link);