netdev - Re: [PATCH v2 2/2] can: spi: hi311x: Add Holt HI-311x CAN driver

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Date:   Fri, 17 Mar 2017 08:39:30 +0100
From:   Wolfgang Grandegger <wg@...ndegger.com>
To:     Akshay Bhat <akshay.bhat@...esys.com>,
        Akshay Bhat <nodeax@...il.com>
Cc:     mkl@...gutronix.de, linux-can@...r.kernel.org,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] can: spi: hi311x: Add Holt HI-311x CAN driver

Hello Akshay,

Am 16.03.2017 um 23:29 schrieb Akshay Bhat:
> Hi Wolfgang,
>
> On 03/16/2017 04:02 PM, Wolfgang Grandegger wrote:
>>
>> Looks much better now! There are message for state changes to error
>> warning and passive. Just the following message is not correct:
>>
>>  (000.200824)  can0  20000004   [8]  00 40 00 00 00 00 5F 19   ERRORFRAME
>>     controller-problem{}
>>     error-counter-tx-rx{{95}{25}}
>>
>> Sorry, forgot to mention... the function can_change_state() [1]
>> should be used for that purpose, if possible. It fixes the issue
>> above as well.
>>
>
> The updated driver (the one used to create the above log) is using
> can_change_state() function. data[1] 40 corresponds to
> CAN_ERR_CRTL_ACTIVE, so looks correct? Could it be that the can-utils I
> am using is old and not reporting state change?

Hm, yes. The raw data looks correct. You could download and build a 
recent version from "https://github.com/linux-can/can-utils" to check. 
It could also be a bug.

> Tentative v4 driver for reference:
> http://pastebin.com/4xFVL1Sj
>
>>> berr-reporting off case:
>>> http://pastebin.com/fUn3j7qU
>>
>> Ditto.
>>
>> I just had another look to the manual and there is this undocumented
>> STATFE register at offset 0x1E. It's mentioned in some other parts of
>> the doc as interrupt enable register for STATF events. I would assume
>> the same bit layout than STATF. If you set bit 2 (BUSOFF), 3 (ERRP)
>> and 4 (ERRW), you may get interrupts. It's worth a try, I think. If
>> it works, it's the much better solution.
>>
>
> The HI-311x has a INT pin and a STAT pin. The hardware I have has only
> the INT pin connected to the processor. If the STAT pin was also
> connected, then like you mentioned it could be a much better solution to
> use STAT for state changes.

OK, I understand.

> Enabling BUSOFF/ERRP/ERRW bits in STATFE did not generate any interrupts
> on the INT pin. Should we make it a requirement that both INT and STAT
> pins need to be connected in hardware for the driver to do the error
> reporting?

As I said, it's the better solution, especially if interrupt flooding 
does harm. How does your system behave when bus errors come in due to no 
cable connected?

So far using NAPI was mandatory. There is the problem of out-of-order 
message reception if handled in the isr on multi processor systems. 
Marc, what is the current policy?

Wolfgang.