[PATCH 4.9 44/44] can: rcar_canfd: rcar_canfd_handle_global_receive(): fix IRQ storm on global FIFO receive

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

From: Biju Das <biju.das.jz@bp.renesas.com>

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/can/rcar/rcar_canfd.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- 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_int
 	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_int
 
 		/* 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,