[PATCH net-next v3 2/4] net: phy: warn if phy_start is called from invalid state

[Heiner Kallweit]

phy_start() should be called from states PHY_READY or PHY_HALTED only.
Check for this to detect misbehaving drivers. Also the state machine
should be started only when being called from one of the valid states.

Some more background:
For all invalid states phy_start() basically was a no-op. All it did
was triggering a state machine run, but for all "running" states the
poll loop was active anyway. And if called from PHY_DOWN, the state
machine does nothing.

v3:
- extended commit message

Signed-off-by: Heiner Kallweit <hkallwe...@gmail.com>
---
 drivers/net/phy/phy.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index 3df6aadc5..fd928979b 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -861,9 +861,16 @@ void phy_start(struct phy_device *phydev)
 
        mutex_lock(&phydev->lock);
 
+       if (phydev->state != PHY_READY && phydev->state != PHY_HALTED) {
+               WARN(1, "called from state %s\n",
+                    phy_state_to_str(phydev->state));
+               goto out;
+       }
+
        switch (phydev->state) {
        case PHY_READY:
                phydev->state = PHY_UP;
+               phy_start_machine(phydev);
                break;
        case PHY_HALTED:
                /* if phy was suspended, bring the physical link up again */
@@ -877,13 +884,13 @@ void phy_start(struct phy_device *phydev)
                }
 
                phydev->state = PHY_RESUMING;
+               phy_start_machine(phydev);
                break;
        default:
                break;
        }
+out:
        mutex_unlock(&phydev->lock);
-
-       phy_start_machine(phydev);
 }
 EXPORT_SYMBOL(phy_start);
 
-- 
2.20.1