linux-kernel - Re: [PATCH] can: flexcan: bump FLEXCAN_TIMEOUT

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Message-ID: <5615c217-8ba6-e452-1aaa-1e3b32eb4cca@prevas.dk>
Date:   Thu, 21 Mar 2019 14:34:41 +0000
From:   Rasmus Villemoes <rasmus.villemoes@...vas.dk>
To:     Marc Kleine-Budde <mkl@...gutronix.de>,
        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>
Subject: Re: [PATCH] can: flexcan: bump FLEXCAN_TIMEOUT_US to 250

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?

Thanks,
Rasmus