[RFC PATCH net v3] net: phy: Fix the issue that netif always links up after resuming

[Kunihiko Hayashi]

Even though the link is down before entering hibernation,
there is an issue that the network interface always links up after resuming
from hibernation.

The phydev->state is PHY_READY before enabling the network interface, so
the link is down. After resuming from hibernation, the phydev->state is
forcibly set to PHY_UP in mdio_bus_phy_restore(), and the link becomes up.

This patch adds a new convenient function to check whether the PHY is in
a started state, and expects to solve the issue by changing phydev->state
to PHY_UP and calling phy_start_machine() only when the PHY is started.

Suggested-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@xxxxxxxxxxxxx>
---

Changes since v2:
 - add mutex lock/unlock for changing phydev->state
 - check whether the mutex is locked in phy_is_started()
 
Changes since v1:
 - introduce a new helper function phy_is_started() and use it instead of
   checking link status
 - replace checking phydev->state with phy_is_started() in
   phy_stop_machine()

drivers/net/phy/phy.c        |  2 +-
 drivers/net/phy/phy_device.c | 12 +++++++++---
 include/linux/phy.h          | 13 +++++++++++++
 3 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index 1d73ac3..f484d03 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -670,7 +670,7 @@ void phy_stop_machine(struct phy_device *phydev)
 	cancel_delayed_work_sync(&phydev->state_queue);
 
 	mutex_lock(&phydev->lock);
-	if (phydev->state > PHY_UP && phydev->state != PHY_HALTED)
+	if (phy_is_started(phydev))
 		phydev->state = PHY_UP;
 	mutex_unlock(&phydev->lock);
 }
diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index ab33d17..4897d24 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -309,10 +309,16 @@ static int mdio_bus_phy_restore(struct device *dev)
 		return ret;
 
 	/* The PHY needs to renegotiate. */
-	phydev->link = 0;
-	phydev->state = PHY_UP;
+	mutex_lock(&phydev->lock);
+	if (phy_is_started(phydev)) {
+		phydev->state = PHY_UP;
+		mutex_unlock(&phydev->lock);
+		phydev->link = 0;
+		phy_start_machine(phydev);
+	} else {
+		mutex_unlock(&phydev->lock);
+	}
 
-	phy_start_machine(phydev);
 
 	return 0;
 }
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 3ea87f7..dd21537 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -898,6 +898,19 @@ static inline bool phy_is_pseudo_fixed_link(struct phy_device *phydev)
 }
 
 /**
+ * phy_is_started - Convenience function for testing whether a PHY is in
+ * a started state
+ * @phydev: the phy_device struct
+ *
+ * The caller must have taken the phy_device mutex lock.
+ */
+static inline bool phy_is_started(struct phy_device *phydev)
+{
+	WARN_ON(!mutex_is_locked(&phydev->lock));
+	return phydev->state >= PHY_UP && phydev->state != PHY_HALTED;
+}
+
+/**
  * phy_write_mmd - Convenience function for writing a register
  * on an MMD on a given PHY.
  * @phydev: The phy_device struct
-- 
2.7.4