[PATCH] can: rcar_canfd: rcar_canfd_handle_global_receive(): fix IRQ storm on global FIFO receive

From: Biju Das <biju.das.jz@bp.renesas.com>
To: Wolfgang Grandegger <wg@grandegger.com>,
	gregkh@linuxfoundation.org,
	Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Biju Das <biju.das.jz@bp.renesas.com>,
	Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>,
	Pavel Machek <pavel@denx.de>, Sasha Levin <sashal@kernel.org>,
	linux-can@vger.kernel.org, netdev@vger.kernel.org,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Chris Paterson <chris.paterson2@renesas.com>,
	linux-renesas-soc@vger.kernel.org, stable@vger.kernel.org,
	#@vger.kernel.org, 4.9.x@vger.kernel.org
Subject: [PATCH] can: rcar_canfd: rcar_canfd_handle_global_receive(): fix IRQ storm on global FIFO receive
Date: Mon, 31 Oct 2022 09:02:25 +0000	[thread overview]
Message-ID: <20221031090225.589321-1-biju.das.jz@bp.renesas.com> (raw)

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@pengutronix.de>
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/all/20221025155657.1426948-2-biju.das.jz@bp.renesas.com
Cc: stable@vger.kernel.org
[mkl: adjust commit message]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
[biju: removed gpriv from RCANFD_RFCC_RFIE macro]
Signed-off-by: Biju Das <biju.das.jz@bp.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

