netdev - [PATCH V2 net-next] net: fec: fix system hang during suspend/resume

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Date:   Tue, 14 Dec 2021 18:50:46 +0800
From:   Joakim Zhang <qiangqing.zhang@....com>
To:     davem@...emloft.net, kuba@...nel.org, andrew@...n.ch
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-imx@....com
Subject: [PATCH V2 net-next] net: fec: fix system hang during suspend/resume

1. During normal suspend (WoL not enabled) process, system has posibility
to hang. The root cause is TXF interrupt coming after clocks disabled,
system hang when accessing registers from interrupt handler. To fix this
issue, disable all interrupts when system suspend.

2. System also has posibility to hang with WoL enabled during suspend,
after entering stop mode, then magic pattern coming after clocks
disabled, system will be waked up, and interrupt handler will be called,
system hang when access registers. To fix this issue, disable wakeup
irq in .suspend(), and enable it in .resume().

Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>
---
Send to net-next although this is a bug fix, since there is no suitable
commit to be blamed, can be back ported to stable tree if others need.

ChangeLogs:
V1->V2:
	* remove inline prefix, let the compiler decide.
---
 drivers/net/ethernet/freescale/fec_main.c | 46 +++++++++++++++++------
 1 file changed, 34 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index 613b8180a1bd..796133de527e 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -1185,6 +1185,21 @@ static void fec_enet_stop_mode(struct fec_enet_private *fep, bool enabled)
 	}
 }
 
+static void fec_irqs_disable(struct net_device *ndev)
+{
+	struct fec_enet_private *fep = netdev_priv(ndev);
+
+	writel(0, fep->hwp + FEC_IMASK);
+}
+
+static void fec_irqs_disable_except_wakeup(struct net_device *ndev)
+{
+	struct fec_enet_private *fep = netdev_priv(ndev);
+
+	writel(0, fep->hwp + FEC_IMASK);
+	writel(FEC_ENET_WAKEUP, fep->hwp + FEC_IMASK);
+}
+
 static void
 fec_stop(struct net_device *ndev)
 {
@@ -1211,15 +1226,13 @@ fec_stop(struct net_device *ndev)
 			writel(1, fep->hwp + FEC_ECNTRL);
 			udelay(10);
 		}
-		writel(FEC_DEFAULT_IMASK, fep->hwp + FEC_IMASK);
 	} else {
-		writel(FEC_DEFAULT_IMASK | FEC_ENET_WAKEUP, fep->hwp + FEC_IMASK);
 		val = readl(fep->hwp + FEC_ECNTRL);
 		val |= (FEC_ECR_MAGICEN | FEC_ECR_SLEEP);
 		writel(val, fep->hwp + FEC_ECNTRL);
-		fec_enet_stop_mode(fep, true);
 	}
 	writel(fep->phy_speed, fep->hwp + FEC_MII_SPEED);
+	writel(FEC_DEFAULT_IMASK, fep->hwp + FEC_IMASK);
 
 	/* We have to keep ENET enabled to have MII interrupt stay working */
 	if (fep->quirks & FEC_QUIRK_ENET_MAC &&
@@ -2877,15 +2890,10 @@ fec_enet_set_wol(struct net_device *ndev, struct ethtool_wolinfo *wol)
 		return -EINVAL;
 
 	device_set_wakeup_enable(&ndev->dev, wol->wolopts & WAKE_MAGIC);
-	if (device_may_wakeup(&ndev->dev)) {
+	if (device_may_wakeup(&ndev->dev))
 		fep->wol_flag |= FEC_WOL_FLAG_ENABLE;
-		if (fep->wake_irq > 0)
-			enable_irq_wake(fep->wake_irq);
-	} else {
+	else
 		fep->wol_flag &= (~FEC_WOL_FLAG_ENABLE);
-		if (fep->wake_irq > 0)
-			disable_irq_wake(fep->wake_irq);
-	}
 
 	return 0;
 }
@@ -4057,9 +4065,19 @@ static int __maybe_unused fec_suspend(struct device *dev)
 		netif_device_detach(ndev);
 		netif_tx_unlock_bh(ndev);
 		fec_stop(ndev);
-		fec_enet_clk_enable(ndev, false);
-		if (!(fep->wol_flag & FEC_WOL_FLAG_ENABLE))
+		if (!(fep->wol_flag & FEC_WOL_FLAG_ENABLE)) {
+			fec_irqs_disable(ndev);
 			pinctrl_pm_select_sleep_state(&fep->pdev->dev);
+		} else {
+			fec_irqs_disable_except_wakeup(ndev);
+			if (fep->wake_irq > 0) {
+				disable_irq(fep->wake_irq);
+				enable_irq_wake(fep->wake_irq);
+			}
+			fec_enet_stop_mode(fep, true);
+		}
+		/* It's safe to disable clocks since interrupts are masked */
+		fec_enet_clk_enable(ndev, false);
 	}
 	rtnl_unlock();
 
@@ -4097,6 +4115,10 @@ static int __maybe_unused fec_resume(struct device *dev)
 		}
 		if (fep->wol_flag & FEC_WOL_FLAG_ENABLE) {
 			fec_enet_stop_mode(fep, false);
+			if (fep->wake_irq) {
+				disable_irq_wake(fep->wake_irq);
+				enable_irq(fep->wake_irq);
+			}
 
 			val = readl(fep->hwp + FEC_ECNTRL);
 			val &= ~(FEC_ECR_MAGICEN | FEC_ECR_SLEEP);
-- 
2.17.1