[PATCH 5.10.y-cip 1/7] 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: cip-dev@lists.cip-project.org,
	Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>,
	Pavel Machek <pavel@denx.de>
Cc: Chris Paterson <chris.paterson2@renesas.com>,
	Biju Das <biju.das.jz@bp.renesas.com>,
	Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com>
Subject: [PATCH 5.10.y-cip 1/7] can: rcar_canfd: rcar_canfd_handle_global_receive(): fix IRQ storm on global FIFO receive
Date: Tue, 13 Dec 2022 17:23:10 +0000	[thread overview]
Message-ID: <20221213172316.1848032-2-biju.das.jz@bp.renesas.com> (raw)
In-Reply-To: <20221213172316.1848032-1-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(-)

diff --git a/drivers/net/can/rcar/rcar_canfd.c b/drivers/net/can/rcar/rcar_canfd.c
index feba57833cdc..f93b44ae4121 100644
--- a/drivers/net/can/rcar/rcar_canfd.c
+++ b/drivers/net/can/rcar/rcar_canfd.c
@@ -1106,11 +1106,13 @@ static void rcar_canfd_handle_global_receive(struct rcar_canfd_global *gpriv, u3
 {
 	struct rcar_canfd_channel *priv = gpriv->ch[ch];
 	u32 ridx = ch + RCANFD_RFFIFO_IDX;
-	u32 sts;
+	u32 sts, cc;
 
 	/* 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


