Re: [PATCH] c_can: Add support for eg20t (pch_can)

[Alexander Stein <alexander.stein@systec-electronic.com>]

On Monday 07 April 2014 17:53:59, Thomas Gleixner wrote:
> On Mon, 7 Apr 2014, Alexander Stein wrote:
> > On Monday 07 April 2014 17:24:26, Thomas Gleixner wrote:
> > > It'd be odd, because we get the buffers with the NEWDAT pending bits
> > > from the NEWDATA1 register.
> >
>  
> > Using the following patch the warning raises about every 5ms. With
> > and without your last patchset.
> 
> > but reverting c0a9f4d39 this does _NOT_ arise.
> 
> So the NEWDAT register is telling us that the newdat bit of that
> buffer is set. But when we retrieve the message, it's not set.
> 
> What's even more confusing: On my D_CAN hardware the NEWDAT is not set
> event happens when I revert c0a9f4d39
> 
> So it would be interesting to see, whether this event is aligned to
> the lost packets you are hunting:
> 
>     P1 -> P2 -> WARN -> P4
> 
> A few trace printks should tell us pretty fast.

I slightly modified my patch (see below) to see which obj is marked with NEWDAT wrongly.
It turns out it is spread over many message objects, but object 1 is notably the one most occuring.
Can it happen, that NEWDAT1 already shows the bit while the NEWDAT bit is not updated yet?
Or does commit c0a9f4d39 affect this status because INTPEND is cleared before reading the message object now?

Regards,
Alexander

diff --git a/drivers/net/can/c_can/c_can.c b/drivers/net/can/c_can/c_can.c
index 0e9f974..f65124a 100644
--- a/drivers/net/can/c_can/c_can.c
+++ b/drivers/net/can/c_can/c_can.c
@@ -836,8 +836,10 @@ static int c_can_read_objects(struct net_device *dev, struct c_can_priv *priv,
 		 * odd HW behaviour. Do not remove that unless you
 		 * want to brick your machine.
 		 */
-		if (!(ctrl & IF_MCONT_NEWDAT))
+		if (!(ctrl & IF_MCONT_NEWDAT)) {
+			netdev_warn(dev, "Odd behavior on obj: %d", obj);
 			continue;
+		}
 
 		/* read the data from the message object */
 		c_can_read_msg_object(dev, IF_RX, ctrl);

-- 
Dipl.-Inf. Alexander Stein

SYS TEC electronic GmbH
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