Re: pch_can: Data transmission stops after dropped packet

[Wolfgang Grandegger <wg@grandegger.com>]

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Hi Michael,

On 11/23/2012 06:52 PM, Michael Pellegrini wrote:
> Wolfgang Grandegger <wg <at> grandegger.com> writes:
> 
>>> That's clear. Therefore please remove that printk for testing. For a
>>> quick test could you please add spin_locks to c_can_do_rx_poll() similar
>>> to c_can_do_tx(). My suspicion is that there is a race in accessing the
>>> message ram. There is this infamous c_can_msg_obj_is_busy() in
>>> c_can_object_get() and c_can_object_put().
>>
>> And please use:
>>
>> CONFIG_CAN_DEBUG_DEVICES=y CONFIG_CAN_C_CAN_PCI=m make -C
>> /usr/src/linux-headers-`uname -r` SUBDIRS=`pwd` modules
>>
>> otherwise we will not have debug messages.
> 
> Ok, I've applied the following patch:
> 
> *** ../c-can-pci-v5/c_can.c	2012-11-21 14:47:03.000000000 -0500
> --- ./c_can.c	2012-11-23 12:27:05.946016919 -0500
> *************** static int c_can_do_rx_poll(struct net_d
> *** 795,800 ****
> --- 795,803 ----
>   	unsigned int msg_obj, msg_ctrl_save;
>   	struct c_can_priv *priv = netdev_priv(dev);
>   	u32 val = c_can_read_reg32(priv, C_CAN_INTPND1_REG);
> + 	unsigned long flags;
> + 
> + 	spin_lock_irqsave(&priv->lock, flags);
>   
>   	for (msg_obj = C_CAN_MSG_OBJ_RX_FIRST;
>   			msg_obj <= C_CAN_MSG_OBJ_RX_LAST && quota > 0;
> *************** static int c_can_do_rx_poll(struct net_d
> *** 843,848 ****
> --- 846,853 ----
>   		}
>   	}
>   
> + 	spin_unlock_irqrestore(&priv->lock, flags);
> + 
>   	return num_rx_pkts;
>   }

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).

Wolfgang.

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