netdev - [PATCH net] net: phy: avoid clearing PHY interrupts twice in irq handler

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Date:   Sun, 1 Mar 2020 21:36:09 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        David Miller <davem@...emloft.net>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Michael Walle <michael@...le.cc>
Subject: [PATCH net] net: phy: avoid clearing PHY interrupts twice in irq
 handler

On all PHY drivers that implement did_interrupt() reading the interrupt
status bits clears them. This means we may loose an interrupt that
is triggered between calling did_interrupt() and phy_clear_interrupt().
As part of the fix make it a requirement that did_interrupt() clears
the interrupt.

The Fixes tag refers to the first commit where the patch applies
cleanly.

Fixes: 49644e68f472 ("net: phy: add callback for custom interrupt handler to struct phy_driver")
Reported-by: Michael Walle <michael@...le.cc>
Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
---
 drivers/net/phy/phy.c | 3 ++-
 include/linux/phy.h   | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index d76e038cf..16e3fb79e 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -727,7 +727,8 @@ static irqreturn_t phy_interrupt(int irq, void *phy_dat)
 		phy_trigger_machine(phydev);
 	}
 
-	if (phy_clear_interrupt(phydev))
+	/* did_interrupt() may have cleared the interrupt already */
+	if (!phydev->drv->did_interrupt && phy_clear_interrupt(phydev))
 		goto phy_err;
 	return IRQ_HANDLED;
 
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 80f8b2158..8b299476b 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -557,6 +557,7 @@ struct phy_driver {
 	/*
 	 * Checks if the PHY generated an interrupt.
 	 * For multi-PHY devices with shared PHY interrupt pin
+	 * Set interrupt bits have to be cleared.
 	 */
 	int (*did_interrupt)(struct phy_device *phydev);
 
-- 
2.25.1