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

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 07/25/2014 08:16 PM, Matthias Klein wrote:
> 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.

For some use cases and users this is important. However I think we all
don't want to have an unresponsive system. Have a look the "can:
berr_limit support" series [1], which introduces a configurable time-out
before the error interrupts are re-enabled.

[1] http://comments.gmane.org/gmane.linux.can/4070

The series needs some polishing and there are some open questions to
address.

Marc

> 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.
> 

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
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