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

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Date:	Wed, 11 Nov 2015 09:04:53 +0100
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	Mirza Krak <mirza.krak@...tmobility.com>, wg@...ndegger.com
Cc:	andri.yngvason@...el.com, linux-can@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] can: sja1000: clear interrupts on start

On 11/10/2015 02:59 PM, Mirza Krak wrote:
> From: Mirza Krak <mirza.krak@...tmobility.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@...tmobility.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

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