Re: sja1000 interrupt problem

[Wolfgang Grandegger <wg@grandegger.com>]

On 11/17/2013 06:23 PM, Wolfgang Grandegger wrote:
> On 11/17/2013 03:27 PM, Oliver Hartkopp wrote:
>>
>>
>> On 17.11.2013 09:18, Wolfgang Grandegger wrote:
>>>
>>> On Sat, 16 Nov 2013 22:42:10 +0100, Oliver Hartkopp
>>
>>
>>>> Btw. I would try two more things with the sja1000.c driver:
>>>
>>>>
>>>
>>>> 1. Print the corresponding CAN device name and the point in the code
>>>
>>> before
>>>
>>>> returning IRQ_NONE to catch the problematic return site.
>>>
>>>>
>>>
>>>> 2. Replace all IRQ_NONE with IRQ_HANDLED for a test ...
>>>
>>>>
>>>
>>>> Any other ideas?
>>>
>>>
>>>
>>> A function trace is still the first thing to take. Be aware that the
>>>
>>> tasks are running on more than one CPU. It's just to establish a good
>>>
>>> trigger.
>>>
>>
>> Yes. But so far the function trace only showed the fact of simultaneous irq
>> treads for the two CAN interfaces - what we were expecting :-)
> 
> Yes, because the trigger was not good so far.
> 
>> IMO it's interesting to get the concrete return site from where the IRQ_NONE
>> is returned. Maybe one of the other interfaces / bits in PITA are enabled
>> which we did not see so far.
> 
> The problem is that the IRQs are shared, also with the ATA disk. There
> it's normal to see unhandled interrupts. My idea was to trigger a
> "tracing_off" after 10 IRQ_NONE in sequence.

See my patch below. @Austin, you may want to give it a try.

Wolfgang.

From eac2b63d114bc83544f806a549fe7339d54c031f Mon Sep 17 00:00:00 2001
From: Wolfgang Grandegger <wg@grandegger.com>
Date: Sun, 17 Nov 2013 21:39:05 +0100
Subject: [PATCH] sja1000: debugging code to inspect too much unhandeled irq

If more than "IRQ_NONE_COUNT_MAX" unhandled interrupts are detected
in sequence, ftracing will be stopped.
---
 drivers/net/can/sja1000/sja1000.c |   34 +++++++++++++++++++++++++++-------
 1 file changed, 27 insertions(+), 7 deletions(-)

diff --git a/drivers/net/can/sja1000/sja1000.c b/drivers/net/can/sja1000/sja1000.c
index 7164a99..80e8d84 100644
--- a/drivers/net/can/sja1000/sja1000.c
+++ b/drivers/net/can/sja1000/sja1000.c
@@ -486,6 +486,9 @@ static int sja1000_err(struct net_device *dev, uint8_t isrc, uint8_t status)
 	return 0;
 }
 
+#define IRQ_NONE_COUNT_MAX 5
+static int irq_none_count;
+
 irqreturn_t sja1000_interrupt(int irq, void *dev_id)
 {
 	struct net_device *dev = (struct net_device *)dev_id;
@@ -496,7 +499,7 @@ irqreturn_t sja1000_interrupt(int irq, void *dev_id)
 
 	/* Shared interrupts and IRQ off? */
 	if (priv->read_reg(priv, SJA1000_IER) == IRQ_OFF)
-		return IRQ_NONE;
+		goto out;
 
 	if (priv->pre_irq)
 		priv->pre_irq(priv);
@@ -506,8 +509,11 @@ irqreturn_t sja1000_interrupt(int irq, void *dev_id)
 		n++;
 		status = priv->read_reg(priv, SJA1000_SR);
 		/* check for absent controller due to hw unplug */
-		if (status == 0xFF && sja1000_is_absent(priv))
-			return IRQ_NONE;
+		if (status == 0xFF && sja1000_is_absent(priv)) {
+			netdev_warn(dev, "controller lost (n=%d)\n", n);
+			n = 0;
+			goto out;
+		}
 
 		if (isrc & IRQ_WUI)
 			netdev_warn(dev, "wakeup interrupt\n");
@@ -534,8 +540,11 @@ irqreturn_t sja1000_interrupt(int irq, void *dev_id)
 				sja1000_rx(dev);
 				status = priv->read_reg(priv, SJA1000_SR);
 				/* check for absent controller */
-				if (status == 0xFF && sja1000_is_absent(priv))
-					return IRQ_NONE;
+				if (status == 0xFF && sja1000_is_absent(priv)) {
+					netdev_warn(dev, "controller lost (n=%d)\n", n);
+					n = 0;
+					goto out;
+				}
 			}
 		}
 		if (isrc & (IRQ_DOI | IRQ_EI | IRQ_BEI | IRQ_EPI | IRQ_ALI)) {
@@ -547,11 +556,22 @@ irqreturn_t sja1000_interrupt(int irq, void *dev_id)
 
 	if (priv->post_irq)
 		priv->post_irq(priv);
-
 	if (n >= SJA1000_MAX_IRQ)
 		netdev_dbg(dev, "%d messages handled in ISR", n);
 
-	return (n) ? IRQ_HANDLED : IRQ_NONE;
+out:
+	if (n) {
+		irq_none_count = 0;
+		return IRQ_HANDLED;
+	} else {
+		irq_none_count++;
+		if (irq_none_count >= IRQ_NONE_COUNT_MAX) {
+			netdev_info(dev, "tracing stopped after %d unhandled irqs)\n",
+				    irq_none_count);
+			tracing_off();
+		}
+		return IRQ_NONE;
+	}
 }
 EXPORT_SYMBOL_GPL(sja1000_interrupt);
 
-- 
1.7.9.5