[PATCH net] net: phy: fix resume handling

[PATCH net] net: phy: fix resume handling

[Russell King]

When a PHY has the BMCR_PDOWN bit set, it may decide to ignore writes
to other registers, or reset the registers to power-on defaults.
Micrel PHYs do this for their interrupt registers.

The current structure of phylib tries to enable interrupts before
resuming (and releasing) the BMCR_PDOWN bit.  This fails, causing
Micrel PHYs to stop working after a suspend/resume sequence if they
are using interrupts.

Fix this by ensuring that the PHY driver resume methods do not take
the phydev->lock mutex themselves, but the callers of phy_resume()
take that lock.  This then allows us to move the call to phy_resume()
before we enable interrupts in phy_start().

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
---
 drivers/net/phy/at803x.c     |  4 ----
 drivers/net/phy/phy.c        |  9 +++------
 drivers/net/phy/phy_device.c | 10 ++++++----
 3 files changed, 9 insertions(+), 14 deletions(-)

diff --git a/drivers/net/phy/at803x.c b/drivers/net/phy/at803x.c
index 5f93e6add563..e911e4990b20 100644
--- a/drivers/net/phy/at803x.c
+++ b/drivers/net/phy/at803x.c
@@ -239,14 +239,10 @@ static int at803x_resume(struct phy_device *phydev)
 {
 	int value;
 
-	mutex_lock(&phydev->lock);
-
 	value = phy_read(phydev, MII_BMCR);
 	value &= ~(BMCR_PDOWN | BMCR_ISOLATE);
 	phy_write(phydev, MII_BMCR, value);
 
-	mutex_unlock(&phydev->lock);
-
 	return 0;
 }
 
diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index 2b1e67bc1e73..ed10d1fc8f59 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -828,7 +828,6 @@ EXPORT_SYMBOL(phy_stop);
  */
 void phy_start(struct phy_device *phydev)
 {
-	bool do_resume = false;
 	int err = 0;
 
 	mutex_lock(&phydev->lock);
@@ -841,6 +840,9 @@ void phy_start(struct phy_device *phydev)
 		phydev->state = PHY_UP;
 		break;
 	case PHY_HALTED:
+		/* if phy was suspended, bring the physical link up again */
+		phy_resume(phydev);
+
 		/* make sure interrupts are re-enabled for the PHY */
 		if (phydev->irq != PHY_POLL) {
 			err = phy_enable_interrupts(phydev);
@@ -849,17 +851,12 @@ void phy_start(struct phy_device *phydev)
 		}
 
 		phydev->state = PHY_RESUMING;
-		do_resume = true;
 		break;
 	default:
 		break;
 	}
 	mutex_unlock(&phydev->lock);
 
-	/* if phy was suspended, bring the physical link up again */
-	if (do_resume)
-		phy_resume(phydev);
-
 	phy_trigger_machine(phydev, true);
 }
 EXPORT_SYMBOL(phy_start);
diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 67f25ac29025..b15b31ca2618 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -135,7 +135,9 @@ static int mdio_bus_phy_resume(struct device *dev)
 	if (!mdio_bus_phy_may_suspend(phydev))
 		goto no_resume;
 
+	mutex_lock(&phydev->lock);
 	ret = phy_resume(phydev);
+	mutex_unlock(&phydev->lock);
 	if (ret < 0)
 		return ret;
 
@@ -1026,7 +1028,9 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
 	if (err)
 		goto error;
 
+	mutex_lock(&phydev->lock);
 	phy_resume(phydev);
+	mutex_unlock(&phydev->lock);
 	phy_led_triggers_register(phydev);
 
 	return err;
@@ -1157,6 +1161,8 @@ int phy_resume(struct phy_device *phydev)
 	struct phy_driver *phydrv = to_phy_driver(phydev->mdio.dev.driver);
 	int ret = 0;
 
+	WARN_ON(!mutex_is_locked(&phydev->lock));
+
 	if (phydev->drv && phydrv->resume)
 		ret = phydrv->resume(phydev);
 
@@ -1639,13 +1645,9 @@ int genphy_resume(struct phy_device *phydev)
 {
 	int value;
 
-	mutex_lock(&phydev->lock);
-
 	value = phy_read(phydev, MII_BMCR);
 	phy_write(phydev, MII_BMCR, value & ~BMCR_PDOWN);
 
-	mutex_unlock(&phydev->lock);
-
 	return 0;
 }
 EXPORT_SYMBOL(genphy_resume);
-- 
2.7.4

Re: [PATCH net] net: phy: fix resume handling

[Andrew Lunn]

On Tue, Dec 12, 2017 at 10:45:36AM +0000, Russell King wrote:
> When a PHY has the BMCR_PDOWN bit set, it may decide to ignore writes
> to other registers, or reset the registers to power-on defaults.
> Micrel PHYs do this for their interrupt registers.
> 
> The current structure of phylib tries to enable interrupts before
> resuming (and releasing) the BMCR_PDOWN bit.  This fails, causing
> Micrel PHYs to stop working after a suspend/resume sequence if they
> are using interrupts.
> 
> Fix this by ensuring that the PHY driver resume methods do not take
> the phydev->lock mutex themselves, but the callers of phy_resume()
> take that lock.  This then allows us to move the call to phy_resume()
> before we enable interrupts in phy_start().
> 
> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew

Re: [PATCH net] net: phy: fix resume handling

[David Miller]

From: Russell King <rmk+kernel@armlinux.org.uk>
Date: Tue, 12 Dec 2017 10:45:36 +0000

> When a PHY has the BMCR_PDOWN bit set, it may decide to ignore writes
> to other registers, or reset the registers to power-on defaults.
> Micrel PHYs do this for their interrupt registers.
> 
> The current structure of phylib tries to enable interrupts before
> resuming (and releasing) the BMCR_PDOWN bit.  This fails, causing
> Micrel PHYs to stop working after a suspend/resume sequence if they
> are using interrupts.
> 
> Fix this by ensuring that the PHY driver resume methods do not take
> the phydev->lock mutex themselves, but the callers of phy_resume()
> take that lock.  This then allows us to move the call to phy_resume()
> before we enable interrupts in phy_start().
> 
> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

Applied.