linux-kernel - Re: [PATCH v3 4/4] can: flexcan: add vf610 support for FlexCAN

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Date:	Mon, 04 Aug 2014 18:01:06 +0200
From:	Stefan Agner <stefan@...er.ch>
To:	Marc Kleine-Budde <mkl@...gutronix.de>
Cc:	shawn.guo@...escale.com, kernel@...gutronix.de,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-can@...r.kernel.org
Subject: Re: [PATCH v3 4/4] can: flexcan: add vf610 support for FlexCAN

Am 2014-08-04 16:27, schrieb Marc Kleine-Budde:
> On 08/04/2014 03:43 PM, Stefan Agner wrote:
> [...]
> 
>>> Thanks for the test, so far looks promising :) With this setup the other
>>> CAN node repeats the CAN frame until it's ACKed. Because there is no
>>> node with a compatible bitrate, there is no ACking CAN node.
>>>
>>> Can you add a third CAN node to the network. The second and third node
>>> should use the same bitrate, while your vf610 uses a different one. With
>>> the new setup it should take more than one frame until the vf610 goes
>>> into error warning and even more frames to error passive. This way we
>>> can see it the error warning interrupt is connected or not. The error
>>> counters should increase with each "wrong" bitrate frame it sees, you
>>> can check with:
>>>
>>>     ip -details link show can0
>>>
>>> The output looks like this:
>>>
>>>> 4: can0: <NOARP,UP,LOWER_UP,ECHO> mtu 16 qdisc pfifo_fast state UNKNOWN mode DEFAULT qlen 10
>>>>     link/can
>>>>     can state ERROR-ACTIVE (berr-counter tx 0 rx 0) restart-ms 0
>>>                               ^^^^^^^^^^^^^^^^^^^^^^
>>>>     bitrate 1000000 sample-point 0.750
>>>>     tq 125 prop-seg 2 phase-seg1 3 phase-seg2 2 sjw 1
>>>>     sja1000: tseg1 1..16 tseg2 1..8 sjw 1..4 brp 1..64 brp-inc 1
>>>>     clock 8000000
>>>
>>> When one of the berr-counter crosses 96 (and stays below 128) a warning
>>> interrupt should be generated.
>>
>> Ok, created this setup, could successfully communicate with all three
>> nodes. I then set the Vybrid to half of the bitrate. When I send a frame
>> from Vybrid, the berr-counter tx immediately ends up at 128 and the
>> device is in ERROR-PASSIVE:
> 
> This is expected.
> 
>> root@...ibri-vf:~# ip -details link show can1
>> 3: can1: <NOARP,UP,LOWER_UP,ECHO> mtu 16 qdisc pfifo_fast state UNKNOWN
>> mode DEFAULT group default qlen 10
>>     link/can  promiscuity 0
>>     can state ERROR-ACTIVE (berr-counter tx 0 rx 0) restart-ms 0
>>     bitrate 124990 sample-point 0.739
>>     tq 347 prop-seg 8 phase-seg1 8 phase-seg2 6 sjw 1
>>     flexcan: tseg1 4..16 tseg2 2..8 sjw 1..4 brp 1..256 brp-inc 1
>>     clock 83368421
>             ^^^^^^^^
> 
> BTW: the can core has a really weird clock rate, have a look at the
> datasheet if you manage to route a 24 MHz clock (or another multiple of
> 8MHz) to the flexcan core. I had a quick glance at the datasheet, if I
> understand it correctly the Fast OSC clock runs with 24 MHz.
> 

This pinmux is actually part of the IPs CTRL register (see CLKSRC).
Currently this is set unconditionally to peripheral clock, which is on
my device 83.3 MHz (500MHz/6). This would be a bit bigger change. Just
thinking how to implement this. Maybe we have to reference a third clock
"osc" and a device tree property fsl,can-clock-osc which one can choose
between "osc" and "per" what do you think?

>> root@...ibri-vf:~# cansend can1 1F334455#1122334455667788
>> interface = can1, family = 29, type = 3, proto = 1
>> root@...ibri-vf:~# [  818.886664] flexcan_irq, esr=00062242
>> [  818.890365] flexcan_irq, ctrl=1c3dac57
>>
>> root@...ibri-vf:~# ip -details link show can1
>> 3: can1: <NOARP,UP,LOWER_UP,ECHO> mtu 16 qdisc pfifo_fast state UNKNOWN
>> mode DEFAULT group default qlen 10
>>     link/can  promiscuity 0
>>     can state ERROR-PASSIVE (berr-counter tx 128 rx 0) restart-ms 0
>>     bitrate 124990 sample-point 0.739
>>     tq 347 prop-seg 8 phase-seg1 8 phase-seg2 6 sjw 1
>>     flexcan: tseg1 4..16 tseg2 2..8 sjw 1..4 brp 1..256 brp-inc 1
>>     clock 83368421
>>
>>
>> When I send the frames from another device on the bus, I can see the rx
>> count incrementing by one on each frame I send. As you expected, the
>> device changes to ERROR-WARNING when crossing the 96 frame boundary:
> 
> This is correct
> 

Just found out when using too high bitrate (500000 vs 125000), the error
counter immediately goes up to 128 (or even beyond) and ends up in
ERROR-PASSIVE:

# ip -details link show can1
[  292.164820] flexcan_get_berr_counter, esr=00000000
[  292.169715] flexcan_get_berr_counter, esr=00040190
3: can1: <NOARP,UP,LOWER_UP,ECHO> mtu 16 qdisc pfifo_fast state UNKNOWN
mode DEFAULT group default qlen 10
    link/can  promiscuity 0
    can state ERROR-PASSIVE (berr-counter tx 0 rx 135) restart-ms 0
    bitrate 298811 sample-point 0.777
    tq 371 prop-seg 3 phase-seg1 3 phase-seg2 2 sjw 1
    flexcan: tseg1 4..16 tseg2 2..8 sjw 1..4 brp 1..256 brp-inc 1
    clock 83368421



>> root@...ibri-vf:~# ip -details link show can1
>> 3: can1: <NOARP,UP,LOWER_UP,ECHO> mtu 16 qdisc pfifo_fast state UNKNOWN
>> mode DEFAULT group default qlen 10
>>     link/can  promiscuity 0
>>     can state ERROR-ACTIVE (berr-counter tx 0 rx 92) restart-ms 0
>>     bitrate 124990 sample-point 0.739
>>     tq 347 prop-seg 8 phase-seg1 8 phase-seg2 6 sjw 1
>>     flexcan: tseg1 4..16 tseg2 2..8 sjw 1..4 brp 1..256 brp-inc 1
>>     clock 83368421
>> root@...ibri-vf:~# [  448.331150] flexcan_irq, esr=0005050a
>> [  448.334851] flexcan_irq, ctrl=1c3dac57
>> ip -details link show can1
>> 3: can1: <NOARP,UP,LOWER_UP,ECHO> mtu 16 qdisc pfifo_fast state UNKNOWN
>> mode DEFAULT group default qlen 10
>>     link/can  promiscuity 0
>>     can state ERROR-WARNING (berr-counter tx 0 rx 102) restart-ms 0
>>     bitrate 124990 sample-point 0.739
>>     tq 347 prop-seg 8 phase-seg1 8 phase-seg2 6 sjw 1
>>     flexcan: tseg1 4..16 tseg2 2..8 sjw 1..4 brp 1..256 brp-inc 1
>>     clock 83368421
> 
>> However, once reaching 128, I don't get another interrupt and the device
>> stays in ERROR-WARNING:
> 
> The contents of the esr reg would be interesting, especially the
> FLT_CONF part.
> 

root@...ridvf61-v11:~# [  222.221651] flexcan_irq, esr=0005050a
[  222.225349] flexcan_irq, ctrl=1c3dac57
ip -details link show can1
[  223.791082] flexcan_get_berr_counter, esr=00000000
[  223.796246] flexcan_get_berr_counter, esr=00040180
3: can1: <NOARP,UP,LOWER_UP,ECHO> mtu 16 qdisc pfifo_fast state UNKNOWN
mode DEFAULT group default qlen 
10
    link/can  promiscuity 0
    can state ERROR-WARNING (berr-counter tx 0 rx 96) restart-ms 0
    bitrate 124990 sample-point 0.739
    tq 347 prop-seg 8 phase-seg1 8 phase-seg2 6 sjw 1
    flexcan: tseg1 4..16 tseg2 2..8 sjw 1..4 brp 1..256 brp-inc 1
    clock 83368421
root@...ridvf61-v11:~# ip -details link show can1
[  243.571175] flexcan_get_berr_counter, esr=00000000
[  243.576343] flexcan_get_berr_counter, esr=00040582
3: can1: <NOARP,UP,LOWER_UP,ECHO> mtu 16 qdisc pfifo_fast state UNKNOWN
mode DEFAULT group default qlen 
10
    link/can  promiscuity 0
    can state ERROR-WARNING (berr-counter tx 0 rx 104) restart-ms 0
    bitrate 124990 sample-point 0.739
    tq 347 prop-seg 8 phase-seg1 8 phase-seg2 6 sjw 1
    flexcan: tseg1 4..16 tseg2 2..8 sjw 1..4 brp 1..256 brp-inc 1
    clock 83368421

...

root@...ridvf61-v11:~# ip -details link show can1
[  299.831192] flexcan_get_berr_counter, esr=00000000
[  299.836358] flexcan_get_berr_counter, esr=00040582
3: can1: <NOARP,UP,LOWER_UP,ECHO> mtu 16 qdisc pfifo_fast state UNKNOWN
mode DEFAULT group default qlen 10
    link/can  promiscuity 0 
    can state ERROR-WARNING (berr-counter tx 0 rx 126) restart-ms 0 
    bitrate 124990 sample-point 0.739 
    tq 347 prop-seg 8 phase-seg1 8 phase-seg2 6 sjw 1
    flexcan: tseg1 4..16 tseg2 2..8 sjw 1..4 brp 1..256 brp-inc 1
    clock 83368421
root@...ridvf61-v11:~# ip -details link show can1
[  302.411025] flexcan_get_berr_counter, esr=00000000
[  302.416195] flexcan_get_berr_counter, esr=00040592
3: can1: <NOARP,UP,LOWER_UP,ECHO> mtu 16 qdisc pfifo_fast state UNKNOWN
mode DEFAULT group default qlen 10
    link/can  promiscuity 0 
    can state ERROR-WARNING (berr-counter tx 0 rx 128) restart-ms 0 
    bitrate 124990 sample-point 0.739 
    tq 347 prop-seg 8 phase-seg1 8 phase-seg2 6 sjw 1
    flexcan: tseg1 4..16 tseg2 2..8 sjw 1..4 brp 1..256 brp-inc 1
    clock 83368421

The FLTCONF is in Error Passive, however the stack did not received that
information. I still have the printk in the interrupt, however I did not
get an interrupt here (while I get one when it switched to
ERROR-WARNING... But it looks like the ERRINT is still pending...


>> 3: can1: <NOARP,UP,LOWER_UP,ECHO> mtu 16 qdisc pfifo_fast state UNKNOWN
>> mode DEFAULT group default qlen 10
>>     link/can  promiscuity 0
>>     can state ERROR-WARNING (berr-counter tx 0 rx 128) restart-ms 0
>>     bitrate 124990 sample-point 0.739
>>     tq 347 prop-seg 8 phase-seg1 8 phase-seg2 6 sjw 1
>>     flexcan: tseg1 4..16 tseg2 2..8 sjw 1..4 brp 1..256 brp-inc 1
>>     clock 83368421
>>
>> Is this the expected behavior on receive?
> 
> No, it should go into error passive if one of the error counters have >
> 127. Maybe this is an error onthe vf610, maybe it's a general flexcan
> problem.
> 
> Marc

--
Stefan
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