net: systemport: Fix wake-up interrupt race during resume

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>

1 files changed, 11 insertions, 17 deletions

diff --git a/drivers/net/ethernet/broadcom/bcmsysport.c b/drivers/net/ethernet/broadcom/bcmsysport.c
index 147045757b10..c57238fce863 100644
--- a/drivers/net/ethernet/broadcom/bcmsysport.c
+++ b/drivers/net/ethernet/broadcom/bcmsysport.c
@@ -1069,9 +1069,6 @@ static void bcm_sysport_resume_from_wol(struct bcm_sysport_priv *priv)
 {
         u32 reg;
 
-        /* Stop monitoring MPD interrupt */
-        intrl2_0_mask_set(priv, INTRL2_0_MPD | INTRL2_0_BRCM_MATCH_TAG);
-
         /* Disable RXCHK, active filters and Broadcom tag matching */
         reg = rxchk_readl(priv, RXCHK_CONTROL);
         reg &= ~(RXCHK_BRCM_TAG_MATCH_MASK <<
@@ -1081,6 +1078,17 @@ static void bcm_sysport_resume_from_wol(struct bcm_sysport_priv *priv)
         /* Clear the MagicPacket detection logic */
         mpd_enable_set(priv, false);
 
+        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");
 }
 
@@ -1105,7 +1113,6 @@ static irqreturn_t bcm_sysport_rx_isr(int irq, void *dev_id)
         struct bcm_sysport_priv *priv = netdev_priv(dev);
         struct bcm_sysport_tx_ring *txr;
         unsigned int ring, ring_bit;
-        u32 reg;
 
         priv->irq0_stat = intrl2_0_readl(priv, INTRL2_CPU_STATUS) &
                           ~intrl2_0_readl(priv, INTRL2_CPU_MASK_STATUS);
@@ -1131,16 +1138,6 @@ static irqreturn_t bcm_sysport_rx_isr(int irq, void *dev_id)
         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 (MPD) interrupt!\n");
-
-        if (priv->irq0_stat & 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);
-        }
-
         if (!priv->is_lite)
                 goto out;
 
@@ -2641,9 +2638,6 @@ static int bcm_sysport_suspend_to_wol(struct bcm_sysport_priv *priv)
         /* 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 | INTRL2_0_BRCM_MATCH_TAG);
-
         netif_dbg(priv, wol, ndev, "entered WOL mode\n");
 
         return 0;