Date:	Sat, 09 Nov 2013 15:47:04 +0100
From:	Wolfgang Grandegger <wg@...ndegger.com>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	netdev@...r.kernel.org, mkl@...gutronix.de,
	linux-can@...r.kernel.org
CC:	linux-sh@...r.kernel.org, vksavl@...il.com
Subject: Re: [PATCH] can: add Renesas R-Car CAN driver

On 11/09/2013 11:53 AM, Wolfgang Grandegger wrote:
> Hi Sergei,
> 
> On 11/09/2013 02:02 AM, Sergei Shtylyov wrote:
>> Hello.
>>
>> On 10/21/2013 11:12 PM, Wolfgang Grandegger wrote:
>>
>>>>     Sorry for the belated reply -- was on vacations.
>>
>>    And again sorry, couldn't get to this due to other things.
>>
>>>>> thanks for your contribution. The patch looks already quite good.
>>>>> Before
>>>>> I find time for a detailed review could you please check error handling
>>>>> and bus-off recovery by reporting the output of "$ candump -td -e
>>>>> any,0:0,#FFFFFFFF" while sending messages to the device ...
>>
>> [...]
>>
>>>> root@...0.0.101:/opt/can-utils# ip -details link show can0
>>>> 2: can0: <NOARP,UP,LOWER_UP,ECHO> mtu 16 qdisc pfifo_fast state UNKNOWN
>>>> qlen 10 link/can
>>>> can state ERROR-PASSIVE (berr-counter tx 128 rx 0) restart-ms 0
>>>> bitrate 297619 sample-point 0.714
>>
>>> Strange, what bitrate did you configure?
>>
>>    300000.
> 
> Ah, OK. It's just a very unusual CAN bitrate. Common are 125k, 250k,
> 500kB, 800kB and 1 MBit/s. Is it your choice?
> 
>>>> tq 480 prop-seg 2 phase-seg1 2 phase-seg2 2 sjw 1
>>>> rcar_can: tseg1 4..16 tseg2 2..8 sjw 1..4 brp 1..1024 brp-inc 1
>>>> clock 49999999
>>
>>> Could you please try if the algorithm works better with 50000000.
>>
>>    It doesn't. Look at the logs below:
> 
> OK, I was mainly confused by the bitrate. Anyway, the bitrate algorithim
> sometimes does not like exotic clock frequencies or bitrates. Then
> manual setting of the bit-timing parameters might be necessary. But that
> seem not the case here.
> 
>>>>> 2. ... with short-circuited CAN high and low and doing some time later
>>>>>          a manual recovery with "ip link set can0 type can restart"
>>
>>>>     Now we have auto recovery only. Manual recovery was tested with the
>>>> first driver version and worked.
>>
>>> What do you mean with "auto recovery"? Auto recovery by the hardware or
>>> via "restart-ms <ms>"? How do you choose between "manual" and "auto"
>>> recovery?
>>
>>    This exact test was done with hardware auto-recovery only. No
>> "restart-ms" was programmed.
> 
> OK, you already explained that in another mail and your driver does not
> use/support hardware auto-recovery any longer.
> 
>>
>>>> Terminal 1:
>>
>>>> root@...0.0.104:/opt/can-utils# ./cangen -n 1 -g 1 can0
>>>> root@...0.0.104:/opt/can-utils# ./cangen -n 1 -g 1 can0
>>>> root@...0.0.104:/opt/can-utils# ./cangen -n 1 -g 1 can0
>>>> root@...0.0.104:/opt/can-utils#
>>
>>>> Terminal 2:
>>
>>>> root@...0.0.104:/opt/can-utils# ./candump -td -e any,0:0,#FFFFFFFF
>>>> (000.000000) can0 2000008C [8] 00 00 08 00 00 00 00 00 ERRORFRAME
>>>> controller-problem{}
>>>> protocol-violation{{tx-dominant-bit-error}{}}
>>>> bus-error
>>>> (000.021147) can0 20000144 [8] 00 00 00 00 00 00 00 00 ERRORFRAME
>>>> controller-problem{}
>>>> bus-off
>>>> restarted-after-bus-off
>>
>>> Why does it get "restarted" directly after the bus-off?
>>
>>    Because we have hardware auto-recovery enabled.
>>
>>>> (011.738522) can0 2000008C [8] 00 00 08 00 00 00 00 00 ERRORFRAME
>>>> controller-problem{}
>>
>>> What controller problem? data[1] is not set for some reasom.
>>
>>    Not comments. Looking into it.
>>
>>>> protocol-violation{{tx-dominant-bit-error}{}}
>>>> bus-error
>>>> (000.021163) can0 20000144 [8] 00 00 00 00 00 00 00 00 ERRORFRAME
>>>> controller-problem{}
>>>> bus-off
>>>> restarted-after-bus-off
>>>> (001.666625) can0 2000008C [8] 00 00 08 00 00 00 00 00 ERRORFRAME
>>>> controller-problem{}
>>>> protocol-violation{{tx-dominant-bit-error}{}}
>>>> bus-error
>>>> (000.021157) can0 20000144 [8] 00 00 00 00 00 00 00 00 ERRORFRAME
>>>> controller-problem{}
>>>> bus-off
>>>> restarted-after-bus-off
>>
>>>> dmesg:
>>>> rcar_can rcar_can.0 can0: Error warning interrupt
>>>> rcar_can rcar_can.0 can0: Error passive interrupt
>>>> rcar_can rcar_can.0 can0: Bus error interrupt:
>>>> rcar_can rcar_can.0 can0: Bit Error (dominant)
>>>> rcar_can rcar_can.0 can0: Error warning interrupt
>>>> rcar_can rcar_can.0 can0: Error passive interrupt
>>
>>> Why are they reported again. You are already in error passive.
>>
>>    Don't know. :-/
> 
> The hardware might not be that smart. Then the software should care.
> 
>>>>> I also wonder if the messages are always sent in order. You could use
>>>>> the program "canfdtest" [1] from the can-utils for validation.
>>
>>>>     This program is PITA. With the driver workaroung it works:
>>
>>> What workaround?
>>
>>    Doesn't matter already, got rid of it.
> 
> OK. BTW: I suggest to run "canfdtest" at *1* MB/s with additional system
> and I/O load and for much longer than a minute to increase the
> probability of an out-of-order transmissions to occur.

That's probably a wrong assumption because "canfdtest" does do a 1ms
sleep after each generated messages :(. Therefore I would try at 125
KBit/s. Sorry for not providing a reliable tool for out-of-order
validation. There is also the "cansequence" program from the Pengutronix
canutils [1], which might be better suited, also to reveal races.

Wolfgang.

[1] http://git.pengutronix.de/?p=tools/canutils.git;a=summary
    http://www.pengutronix.de/software/socket-can/download

Wolfgang.
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