linux-kernel - [PATCH] can: don't count arbitration lose as an error

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Message-Id: <20201127095941.21609-1-jhofstee@victronenergy.com>
Date:   Fri, 27 Nov 2020 10:59:38 +0100
From:   Jeroen Hofstee <jhofstee@...tronenergy.com>
To:     linux-can@...r.kernel.org
Cc:     Jeroen Hofstee <jhofstee@...tronenergy.com>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        netdev@...r.kernel.org (open list:NETWORKING DRIVERS),
        linux-kernel@...r.kernel.org (open list),
        linux-arm-kernel@...ts.infradead.org (moderated list:ARM/Allwinner
        sunXi SoC support)
Subject: [PATCH] can: don't count arbitration lose as an error

Losing arbitration is normal in a CAN-bus network, it means that a
higher priority frame is being send and the pending message will be
retried later. Hence most driver only increment arbitration_lost, but
the sja1000 and sun4i driver also incremeant tx_error, causing errors
to be reported on a normal functioning CAN-bus. So stop counting them
as errors.

For completeness, the Kvaser USB hybra also increments the tx_error
on arbitration lose, but it does so in single shot. Since in that
case the message is not retried, that behaviour is kept.

Signed-off-by: Jeroen Hofstee <jhofstee@...tronenergy.com>
---
 drivers/net/can/sja1000/sja1000.c | 1 -
 drivers/net/can/sun4i_can.c       | 1 -
 2 files changed, 2 deletions(-)

diff --git a/drivers/net/can/sja1000/sja1000.c b/drivers/net/can/sja1000/sja1000.c
index 9f107798f904..25a4d7d0b349 100644
--- a/drivers/net/can/sja1000/sja1000.c
+++ b/drivers/net/can/sja1000/sja1000.c
@@ -474,7 +474,6 @@ static int sja1000_err(struct net_device *dev, uint8_t isrc, uint8_t status)
 		netdev_dbg(dev, "arbitration lost interrupt\n");
 		alc = priv->read_reg(priv, SJA1000_ALC);
 		priv->can.can_stats.arbitration_lost++;
-		stats->tx_errors++;
 		cf->can_id |= CAN_ERR_LOSTARB;
 		cf->data[0] = alc & 0x1f;
 	}
diff --git a/drivers/net/can/sun4i_can.c b/drivers/net/can/sun4i_can.c
index e2c6cf4b2228..b3f2f4fe5ee0 100644
--- a/drivers/net/can/sun4i_can.c
+++ b/drivers/net/can/sun4i_can.c
@@ -604,7 +604,6 @@ static int sun4i_can_err(struct net_device *dev, u8 isrc, u8 status)
 		netdev_dbg(dev, "arbitration lost interrupt\n");
 		alc = readl(priv->base + SUN4I_REG_STA_ADDR);
 		priv->can.can_stats.arbitration_lost++;
-		stats->tx_errors++;
 		if (likely(skb)) {
 			cf->can_id |= CAN_ERR_LOSTARB;
 			cf->data[0] = (alc >> 8) & 0x1f;
-- 
2.17.1