Re: sja1000 interrupt problem

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

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On 12/13/2013 10:38 AM, Oliver Hartkopp wrote:
[...]

> So after some time all CAN related interrupts have been disabled ...
> 
> I wondered if the PITA access for consuming the bit is really working.
> Therefore I made the if-statement a while statement here:
> 
> --- linux-source-3.10/drivers/net/can/sja1000/peak_pci.c	2013-09-08 07:10:14.000000000 +0200
> +++ linux-source-3.10-rt/drivers/net/can/sja1000/peak_pci.c	2013-12-13 08:42:15.850192329 +0100
> @@ -539,12 +539,17 @@
>  static void peak_pci_post_irq(const struct sja1000_priv *priv)
>  {
>  	struct peak_pci_chan *chan = priv->priv;
> +#if 0
>  	u16 icr;
>  
>  	/* Select and clear in PITA stored interrupt */
>  	icr = readw(chan->cfg_base + PITA_ICR);
>  	if (icr & chan->icr_mask)
>  		writew(chan->icr_mask, chan->cfg_base + PITA_ICR);
> +#else
> +	while (readw(chan->cfg_base + PITA_ICR) & chan->icr_mask)
> +		writew(chan->icr_mask, chan->cfg_base + PITA_ICR);
> +#endif
>  }
>  
>  static int peak_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
> 
> 
> This should usually not have any effect, right?
> But what happened was a big crash after a pretty short time:
> 
> [  760.718091] INFO: rcu_preempt self-detected stall on CPU { 1}  (t=84015 jiffies g=482 c=481 q=2688)

For me it seems that the new while loop keeps spinning and then the rcu
subsystem detects some stalls.

Maybe it's time to get in touch with the hardware engineers at peak.

Marc

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