[PATCH 2/5] net: can: flexcan: disable error interrupts in non ERR-Active state

[Matthias Klein <matthias.klein@optimeas.de>]

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

On imx53 I receive continuously STF_ERR error interrupts after sending a
CAN frame on an open BUS.
This patch disables error interrupts once we leave the ERR-Active state
since I doubt further error interrupts are of any interest especially if
they render the system unresponsible.
According to the manual in this case the system remains in passive state
and RX-err counter is >127 and won't increment any further and so it
won't enter BUS-Off state. Once the system receives a CAN message, the
RX-error counter should by set to 119 … 127 which brings the CAN module
back to ERR-active state which then should activate error reporting
again.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Matthias Klein <matthias.klein@optimeas.de>
---
 drivers/net/can/flexcan.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
index f677b49..2b98da2 100644
--- a/drivers/net/can/flexcan.c
+++ b/drivers/net/can/flexcan.c
@@ -628,7 +628,17 @@ static int flexcan_poll(struct napi_struct *napi, int quota)
 		napi_complete(napi);
 		/* enable IRQs */
 		flexcan_write(FLEXCAN_IFLAG_DEFAULT, &regs->imask1);
-		flexcan_write(priv->reg_ctrl_default, &regs->ctrl);
+		/*
+		 * On an open CAN-bus the iMX51 keeps reporting the STF_ERR
+		 * event after an attempt to send a CAN message. This will
+		 * disable further error reports (or that one that keeps
+		 * nagging) once we leave the ERR-Active state.
+		 */
+		if (reg_esr & FLEXCAN_ESR_FLT_CONF_MASK)
+			flexcan_write(priv->reg_ctrl_default &
+					~FLEXCAN_CTRL_ERR_MSK, &regs->ctrl);
+		else
+			flexcan_write(priv->reg_ctrl_default, &regs->ctrl);
 	}
 
 	return work_done;
@@ -656,8 +666,8 @@ static irqreturn_t flexcan_irq(int irq, void *dev_id)
 	 * - bus error IRQ and bus error reporting is activated
 	 */
 	if ((reg_iflag1 & FLEXCAN_IFLAG_RX_FIFO_AVAILABLE) ||
-	    (reg_esr & FLEXCAN_ESR_ERR_STATE) ||
-	    flexcan_has_and_handle_berr(priv, reg_esr)) {
+	    (reg_esr & FLEXCAN_ESR_ERR_ALL)) {
+
 		/*
 		 * The error bits are cleared on read,
 		 * save them for later use.
-- 
2.0.1