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Date:   Mon, 31 Oct 2022 09:04:20 +0000
From:   Biju Das <biju.das.jz@...renesas.com>
To:     Wolfgang Grandegger <wg@...ndegger.com>,
        gregkh@...uxfoundation.org, Marc Kleine-Budde <mkl@...gutronix.de>
Cc:     Biju Das <biju.das.jz@...renesas.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Pavel Machek <pavel@...x.de>, Sasha Levin <sashal@...nel.org>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Chris Paterson <chris.paterson2@...esas.com>,
        linux-renesas-soc@...r.kernel.org, stable@...r.kernel.org
Subject: [PATCH] can: rcar_canfd: rcar_canfd_handle_global_receive(): fix IRQ storm on global FIFO receive

commit 702de2c21eed04c67cefaaedc248ef16e5f6b293 upstream.

We are seeing an IRQ storm on the global receive IRQ line under heavy
CAN bus load conditions with both CAN channels enabled.

Conditions:

The global receive IRQ line is shared between can0 and can1, either of
the channels can trigger interrupt while the other channel's IRQ line
is disabled (RFIE).

When global a receive IRQ interrupt occurs, we mask the interrupt in
the IRQ handler. Clearing and unmasking of the interrupt is happening
in rx_poll(). There is a race condition where rx_poll() unmasks the
interrupt, but the next IRQ handler does not mask the IRQ due to
NAPIF_STATE_MISSED flag (e.g.: can0 RX FIFO interrupt is disabled and
can1 is triggering RX interrupt, the delay in rx_poll() processing
results in setting NAPIF_STATE_MISSED flag) leading to an IRQ storm.

This patch fixes the issue by checking IRQ active and enabled before
handling the IRQ on a particular channel.

Fixes: dd3bd23eb438 ("can: rcar_canfd: Add Renesas R-Car CAN FD driver")
Suggested-by: Marc Kleine-Budde <mkl@...gutronix.de>
Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
Link: https://lore.kernel.org/all/20221025155657.1426948-2-biju.das.jz@bp.renesas.com
Cc: stable@...r.kernel.org # 4.9.x
[mkl: adjust commit message]
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
[biju: removed gpriv from RCANFD_RFCC_RFIE macro]
Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
---
Resending to 4.9 with confilcts[1] fixed
[1] https://lore.kernel.org/stable/OS0PR01MB59226F2443DFCE7C5D73778786379@OS0PR01MB5922.jpnprd01.prod.outlook.com/T/#t
---
 drivers/net/can/rcar/rcar_canfd.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/can/rcar/rcar_canfd.c b/drivers/net/can/rcar/rcar_canfd.c
index a127c853a4e9..694a3354554f 100644
--- a/drivers/net/can/rcar/rcar_canfd.c
+++ b/drivers/net/can/rcar/rcar_canfd.c
@@ -1079,7 +1079,7 @@ static irqreturn_t rcar_canfd_global_interrupt(int irq, void *dev_id)
 	struct rcar_canfd_global *gpriv = dev_id;
 	struct net_device *ndev;
 	struct rcar_canfd_channel *priv;
-	u32 sts, gerfl;
+	u32 sts, cc, gerfl;
 	u32 ch, ridx;
 
 	/* Global error interrupts still indicate a condition specific
@@ -1097,7 +1097,9 @@ static irqreturn_t rcar_canfd_global_interrupt(int irq, void *dev_id)
 
 		/* Handle Rx interrupts */
 		sts = rcar_canfd_read(priv->base, RCANFD_RFSTS(ridx));
-		if (likely(sts & RCANFD_RFSTS_RFIF)) {
+		cc = rcar_canfd_read(priv->base, RCANFD_RFCC(ridx));
+		if (likely(sts & RCANFD_RFSTS_RFIF &&
+			   cc & RCANFD_RFCC_RFIE)) {
 			if (napi_schedule_prep(&priv->napi)) {
 				/* Disable Rx FIFO interrupts */
 				rcar_canfd_clear_bit(priv->base,
-- 
2.25.1

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