netdev - Re: [PATCH] can: flexcan: bump FLEXCAN_TIMEOUT

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Date:   Fri, 22 Mar 2019 08:51:00 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Rasmus Villemoes <rasmus.villemoes@...vas.dk>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        "David S. Miller" <davem@...emloft.net>
Cc:     Thomas Winding <twi@...f.com>, Fabio Estevam <festevam@...il.com>,
        Per Christensen <pnc@...f.com>,
        Rasmus Villemoes <Rasmus.Villemoes@...vas.se>,
        "linux-can@...r.kernel.org" <linux-can@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Joakim Zhang <qiangqing.zhang@....com>
Subject: Re: [PATCH] can: flexcan: bump FLEXCAN_TIMEOUT_US to 250

On 3/22/19 8:45 AM, Rasmus Villemoes wrote:
> On 21/03/2019 16.30, Marc Kleine-Budde wrote:
>> On 3/21/19 3:34 PM, Rasmus Villemoes wrote:
>>> On 20/03/2019 14.18, Marc Kleine-Budde wrote:
>>>> On 3/7/19 4:00 PM, Rasmus Villemoes wrote:
>>>>> While trying to add support for the Flexcan modules on the MPC8309,
>>>>> I'm hitting ETIMEDOUT in flexcan_chip_disable(). With this, probing
>>>>> succeeds. Checking the leftover value of timeout with a primitive
>>>>>
>>>>>   pr_err("%s: timeout==%d\n", __func__, timeout);
>>>>>
>>>>> after the loop in chip_disable() typically shows values around 12-14,
>>>>> i.e. suggesting that it takes about 110-130 us for the LPM_ACK bit to
>>>>> appear. So a timeout value of about twice that seems reasonable.
>>>>>
>>>>> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@...vas.dk>
>>>>
>>>> I've scheduled the patch by Joakim Zhang:
>>>>
>>>>     9daed89ae8a3 can: flexcan: fix timeout when set small bitrate
>>>>
>>>> that doubles the timeout to 100.
>>>
>>> Eh, ok, but that's not sufficient for the MPC8309 (I tried with 100 at
>>> first, but as I write the minimally working timeout value turns out to
>>> be about 140 us). Do you want me to send another patch on top of
>>> 9daed89ae8a3, or how should I interpret the above?
>>
>> Can you propose an updated commit message for Joakim Zhang's patch?
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/mkl/linux-can.git/commit/?h=testing&id=9daed89ae8a3fc44ccd2b2bb9c3c4d3e3431904d
>>
>> I'll add it by hand and increase the timeout to 250. Ok?
> 
> Sounds fine. In order not to change Joakim's commit log too much, how
> about adding something like (with your initials, since you're next in
> the sign-off chain)
> 
> [mkl: Meanwhile, Rasmus Villemoes reported that even with a timeout of
> 100, flexcan_probe() fails on the MPC8309, which requires a value of at
> least 140 to work reliably. 250 works for everyone.]
> 
> ? Feel free to edit as you wish.

Thanks, I've added that to the commit message itself.

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
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