Re: [PATCH 1/1] can: sja1000: clear interrupts on start

Marc Kleine-Budde
2015-11-11T08:05:09Z

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On 11/10/2015 02:59 PM, Mirza Krak wrote:
> From: Mirza Krak <mirza.krak@hostmobility.com>
>
> According to SJA1000 data sheet error-warning (EI) interrupt is not
> cleared by setting the controller in to reset-mode.
>
> Then if we have the following case:
> - system is suspended (echo mem > /sys/power/state) and SJA1000 is left
> in operating state

This problem occurs only an hardware, where the SJA1000 is powered
during system suspend?

> - A bus error condition occurs which activates EI interrupt, system is
> still suspended which means EI interrupt will be not be handled nor
> cleared.
>
> If the above two events occur, on resume there is no way to return the
> SJA1000 to operating state, except to cycle power to it.
>
> By simply reading the IR register on start we will clear any previous
> conditions that could be present.

Doesn't the SJA1000 trigger an interrupt that is detected after
resuming? You add the fix to the open() function, which is triggered
during $(ifconfig up), how is related to suspend/resume? Does the
network layer call $(ifconfig down) during shutdown?

There isn't any suspend/resume code in the sja1000 driver, for me it
seems that we should add resume code that handles this problem.

>
> Signed-off-by: Mirza Krak <mirza.krak@hostmobility.com>
> ---
> drivers/net/can/sja1000/sja1000.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/net/can/sja1000/sja1000.c b/drivers/net/can/sja1000/sja1000.c
> index 7b92e911a616..f10834be48a5 100644
> --- a/drivers/net/can/sja1000/sja1000.c
> +++ b/drivers/net/can/sja1000/sja1000.c
> @@ -218,6 +218,9 @@ static void sja1000_start(struct net_device *dev)
> priv->write_reg(priv, SJA1000_RXERR, 0x0);
> priv->read_reg(priv, SJA1000_ECC);
>
> + /* clear interrupt flags */
> + priv->read_reg(priv, SJA1000_IR);
> +
> /* leave reset mode */
> set_normal_mode(dev);
> }
>

Marc

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