[PATCH 4.4 29/48] net: systemport: Fix wake-up interrupt race during resume

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Florian Fainelli <f.fainelli@gmail.com>

[ Upstream commit 45ec318578c0c22a11f5b9927d064418e1ab1905 ]

The AON_PM_L2 is normally used to trigger and identify the source of a
wake-up event. Since the RX_SYS clock is no longer turned off, we also
have an interrupt being sent to the SYSTEMPORT INTRL_2_0 controller, and
that interrupt remains active up until the magic packet detector is
disabled which happens much later during the driver resumption.

The race happens if we have a CPU that is entering the SYSTEMPORT
INTRL2_0 handler during resume, and another CPU has managed to clear the
wake-up interrupt during bcm_sysport_resume_from_wol(). In that case, we
have the first CPU stuck in the interrupt handler with an interrupt
cause that has been cleared under its feet, and so we keep returning
IRQ_NONE and we never make any progress.

This was not a problem before because we would always turn off the
RX_SYS clock during WoL, so the SYSTEMPORT INTRL2_0 would also be turned
off as well, thus not latching the interrupt.

The fix is to make sure we do not enable either the MPD or
BRCM_TAG_MATCH interrupts since those are redundant with what the
AON_PM_L2 interrupt controller already processes and they would cause
such a race to occur.

Fixes: bb9051a2b230 ("net: systemport: Add support for WAKE_FILTER")
Fixes: 83e82f4c706b ("net: systemport: add Wake-on-LAN support")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/ethernet/broadcom/bcmsysport.c |   22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

--- a/drivers/net/ethernet/broadcom/bcmsysport.c
+++ b/drivers/net/ethernet/broadcom/bcmsysport.c
@@ -850,14 +850,22 @@ static void bcm_sysport_resume_from_wol(
 {
 	u32 reg;
 
-	/* Stop monitoring MPD interrupt */
-	intrl2_0_mask_set(priv, INTRL2_0_MPD);
-
 	/* Clear the MagicPacket detection logic */
 	reg = umac_readl(priv, UMAC_MPD_CTRL);
 	reg &= ~MPD_EN;
 	umac_writel(priv, reg, UMAC_MPD_CTRL);
 
+	reg = intrl2_0_readl(priv, INTRL2_CPU_STATUS);
+	if (reg & INTRL2_0_MPD)
+		netdev_info(priv->netdev, "Wake-on-LAN (MPD) interrupt!\n");
+
+	if (reg & INTRL2_0_BRCM_MATCH_TAG) {
+		reg = rxchk_readl(priv, RXCHK_BRCM_TAG_MATCH_STATUS) &
+				  RXCHK_BRCM_TAG_MATCH_MASK;
+		netdev_info(priv->netdev,
+			    "Wake-on-LAN (filters 0x%02x) interrupt!\n", reg);
+	}
+
 	netif_dbg(priv, wol, priv->netdev, "resumed from WOL\n");
 }
 
@@ -890,11 +898,6 @@ static irqreturn_t bcm_sysport_rx_isr(in
 	if (priv->irq0_stat & INTRL2_0_TX_RING_FULL)
 		bcm_sysport_tx_reclaim_all(priv);
 
-	if (priv->irq0_stat & INTRL2_0_MPD) {
-		netdev_info(priv->netdev, "Wake-on-LAN interrupt!\n");
-		bcm_sysport_resume_from_wol(priv);
-	}
-
 	return IRQ_HANDLED;
 }
 
@@ -1915,9 +1918,6 @@ static int bcm_sysport_suspend_to_wol(st
 	/* UniMAC receive needs to be turned on */
 	umac_enable_set(priv, CMD_RX_EN, 1);
 
-	/* Enable the interrupt wake-up source */
-	intrl2_0_mask_clear(priv, INTRL2_0_MPD);
-
 	netif_dbg(priv, wol, ndev, "entered WOL mode\n");
 
 	return 0;