[PATCH net v4 2/5] net: phy: disable the line of a postponed PHY interrupt only once

[Igor Velkov via B4 Relay]

From: Igor Velkov <iav at iav.lv>

phy_interrupt() postpones interrupts during a system sleep transition:
it sets irq_rerun and disables the line, and mdio_bus_phy_resume()
re-enables the line once and reruns the handler. On an edge-triggered
line the IRQ core does not mask a ONESHOT interrupt, so an edge that
arrives before disable_irq_nosync() runs the thread again. That second
run disables the line again, and the line stays disabled after resume.

Make irq_rerun atomic, as the next patch adds a second setter, and let
only the run that sets it disable the line. Mark the irq_suspended
accesses with READ_ONCE() and WRITE_ONCE(): the handler reads it while
the PM callbacks write it.

Fixes: 1758bde2e4aa ("net: phy: Don't trigger state machine while in suspend")
Signed-off-by: Igor Velkov <iav at iav.lv>
---
 drivers/net/phy/phy.c        | 7 ++++---
 drivers/net/phy/phy_device.c | 7 +++----
 include/linux/phy.h          | 5 ++---
 3 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index 9af303d60bd6..b47f0d3d99e5 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -1416,7 +1416,7 @@ static irqreturn_t phy_interrupt(int irq, void *phy_dat)
 	/* Wakeup interrupts may occur during a system sleep transition.
 	 * Postpone handling until the PHY has resumed.
 	 */
-	if (IS_ENABLED(CONFIG_PM_SLEEP) && phydev->irq_suspended) {
+	if (IS_ENABLED(CONFIG_PM_SLEEP) && READ_ONCE(phydev->irq_suspended)) {
 		struct net_device *netdev = phydev->attached_dev;
 
 		if (netdev) {
@@ -1430,8 +1430,9 @@ static irqreturn_t phy_interrupt(int irq, void *phy_dat)
 				pm_wakeup_dev_event(parent, 0, true);
 		}
 
-		phydev->irq_rerun = true;
-		disable_irq_nosync(irq);
+		/* Disable the line only once: an edge can rerun the thread. */
+		if (!atomic_xchg(&phydev->irq_rerun, 1))
+			disable_irq_nosync(irq);
 		return IRQ_HANDLED;
 	}
 
diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 79dba43d703a..d5d0efc10418 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -344,7 +344,7 @@ static __maybe_unused int mdio_bus_phy_suspend(struct device *dev)
 	 * has resumed. Wait for concurrent interrupt handler to complete.
 	 */
 	if (phy_interrupt_is_valid(phydev)) {
-		phydev->irq_suspended = true;
+		WRITE_ONCE(phydev->irq_suspended, true);
 		synchronize_irq(phydev->irq);
 	}
 
@@ -394,14 +394,13 @@ static __maybe_unused int mdio_bus_phy_resume(struct device *dev)
 		return ret;
 no_resume:
 	if (phy_interrupt_is_valid(phydev)) {
-		phydev->irq_suspended = false;
+		WRITE_ONCE(phydev->irq_suspended, false);
 		synchronize_irq(phydev->irq);
 
 		/* Rerun interrupts which were postponed by phy_interrupt()
 		 * because they occurred during the system sleep transition.
 		 */
-		if (phydev->irq_rerun) {
-			phydev->irq_rerun = false;
+		if (atomic_xchg(&phydev->irq_rerun, 0)) {
 			enable_irq(phydev->irq);
 			irq_wake_thread(phydev->irq, phydev);
 		}
diff --git a/include/linux/phy.h b/include/linux/phy.h
index bbe28ff97e51..48b4e852f230 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -651,8 +651,7 @@ struct phy_oatc14_sqi_capability {
  * @interrupts: Flag interrupts have been enabled
  * @irq_suspended: Flag indicating PHY is suspended and therefore interrupt
  *                 handling shall be postponed until PHY has resumed
- * @irq_rerun: Flag indicating interrupts occurred while PHY was suspended,
- *             requiring a rerun of the interrupt handler after resume
+ * @irq_rerun: Set by the postponed interrupt that disabled the line
  * @default_timestamp: Flag indicating whether we are using the phy
  *		       timestamp as the default one
  * @interface: enum phy_interface_t value
@@ -728,7 +727,7 @@ struct phy_device {
 	unsigned interrupts:1;
 	/* Written without phydev->lock, so not bitfields */
 	bool irq_suspended;
-	bool irq_rerun;
+	atomic_t irq_rerun;
 
 	unsigned default_timestamp:1;
 

-- 
2.43.0