Re: pch_can: Data transmission stops after dropped packet

[Wolfgang Grandegger <wg@grandegger.com>]

On 11/26/2012 03:54 PM, Michael Pellegrini wrote:
> Wolfgang Grandegger <wg <at> grandegger.com> writes:
> 
>> There is a return in the critical section which must also be handled.
>> Hope you didn't hit it...
>>
>> I have attached v7 fixing this issue. Furthermore I have added spinlock
>> protection to the PCH driver. It needs fixing, even if I want to get
>> ride of it as soon as possible. Could you please give this driver a try
>> as well? The README tells how to build the modules. I will also send my
>> current patch stack for the record (and feedback).
> 
> Oops, I missed that return.  Looks like the system didn't hit it though,
> the CAN interface was still functional after running continuously over the 
> weekend.

Not too bad! The return does only happen at high load. When you
"ifconfig up" the device some kernel messages are printed. Could you
please show them. I want to understand if the reset really occurs by
checking some register values.

> I tried the PCH driver and hit the transmission failure within a minute.

Ah. In the function pch_xmit(), could you please move

	spin_unlock_irqrestore(&priv->lock, flags);

to the end of the function just before

 	return NETDEV_TX_OK;

and then retry. This would fix races with accessing the message ram as
well (via pch_can_rw_msg_obj). I missed that.

> I'm happy to test out more changes to this driver if you think it is worth
> pursuing.

Remote debugging is slow, unfortunately. Thanks for your patience.

> I started a test with the new c_can driver.  I'll check on it throughout
> the day and let it run overnight as well.

OK, apart from the return issue above the driver has not changed from
the functional point of view.

Wolfgang.