can: rcar_canfd: rcar_canfd_handle_global_receive(): fix IRQ storm on global FIFO...

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>

diff --git a/drivers/net/can/rcar/rcar_canfd.c b/drivers/net/can/rcar/rcar_canfd.c
index 567620d..ea828c1 100644 (file)
--- a/drivers/net/can/rcar/rcar_canfd.c
+++ b/drivers/net/can/rcar/rcar_canfd.c
@@ -1157,11 +1157,13 @@ 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(gpriv, ridx));
-       if (likely(sts & RCANFD_RFSTS_RFIF)) {
+       cc = rcar_canfd_read(priv->base, RCANFD_RFCC(gpriv, 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,