From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wolfgang Grandegger <wg@grandegger.com>
Subject: Re: c_can driver sometimes sends first two bytes filled with zeros
Date: Mon, 23 May 2016 20:19:39 +0200
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To: Richard Andrysek <richard.andrysek@gomtec.de>, "linux-can@vger.kernel.org" <linux-can@vger.kernel.org>

Hello,

Am 12.05.2016 um 11:23 schrieb Richard Andrysek:
> We can reproduce an issue with the canutils. We send messages in the loop with non-zero bytes and from time to time we get first two bytes of the message with zero values. The test script looks so:
>
> #!/bin/sh
>
> echo "Press [CTRL+C] to stop.."
> while true
> do
>                 cansend can1 --loop=15 -i 933 0xde 0xde 0xde 0xde 0xde 0xde
> done
>
> With CAN analyzer we see normally the right message, but in cycles ~1min we see first two bytes are zero.
>
> If we add some delays between messages, like this:
>
> do
>                 cansend can1 --loop=1 -i 933 0xde 0xde 0xde 0xde 0xde 0xde
>                 usleep 5
> 	cansend can1 --loop=1 -i 933 0xde 0xde 0xde 0xde 0xde 0xde
>                 usleep 5
> 	cansend can1 --loop=1 -i 933 0xde 0xde 0xde 0xde 0xde 0xde
>                 usleep 5
> 	cansend can1 --loop=1 -i 933 0xde 0xde 0xde 0xde 0xde 0xde
>                 usleep 5
> 	cansend can1 --loop=1 -i 933 0xde 0xde 0xde 0xde 0xde 0xde
>                 usleep 5
> 	cansend can1 --loop=1 -i 933 0xde 0xde 0xde 0xde 0xde 0xde
>                 usleep 5
> 	cansend can1 --loop=1 -i 933 0xde 0xde 0xde 0xde 0xde 0xde
>                 usleep 5
> 	cansend can1 --loop=1 -i 933 0xde 0xde 0xde 0xde 0xde 0xde
>                 usleep 5
> 	cansend can1 --loop=1 -i 933 0xde 0xde 0xde 0xde 0xde 0xde
>                 usleep 5
> 	cansend can1 --loop=1 -i 933 0xde 0xde 0xde 0xde 0xde 0xde
>                 usleep 5
> 	cansend can1 --loop=1 -i 933 0xde 0xde 0xde 0xde 0xde 0xde
>                 usleep 5
>
> done
>
> It works fine.
>
> We use Altera Cyclone V, where the  c_can driver is used. It runs with Linux kernel 3.16, but I've checked 4.5 version of a driver and it is a same one.
>
> Have somebody idea how to find a reason for that?

The official "cansend" does not support "--loop". The official canutils
have cangen and canfdtest for more thorough testing. Anyway, does
"ip -s -d link show" report any errors? And could you run
"candump any,0:0,#FFFFFFFF" while sending. Does it also list the 
messages with the wrong data?

Wolfgang.