> -----Original Message-----
> From: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
> Sent: 2019年11月12日 17:08
> To: Joakim Zhang <qiangqing.zhang@xxxxxxx>; sean@xxxxxxxxxx;
> linux-can@xxxxxxxxxxxxxxx
> Subject: Re: Wake up issue about Flexcan driver in v5.4 kernel
>
> On 11/12/19 10:01 AM, Joakim Zhang wrote:
> >
> >> -----Original Message-----
> >> From: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
> >> Sent: 2019年11月12日 16:38
> >> To: Joakim Zhang <qiangqing.zhang@xxxxxxx>; sean@xxxxxxxxxx;
> >> linux-can@xxxxxxxxxxxxxxx
> >> Subject: Re: Wake up issue about Flexcan driver in v5.4 kernel
> >>
> >> On 11/12/19 8:12 AM, Joakim Zhang wrote:
> >>> I dump some info in wake up case from v5.3.10 with below change:
> >>> printk("\nmailbox_num = %u, timestamp = %u, can_id = %x\n", n,
> >>> *timestamp, cf->can_id);
> >>
> >> Keep in mind, a printk() compared to a trace_printk() will introduce
> >> bigger latencies.
> >
> > Thanks Marc, I will learn how to use trace_printk() later as it cannot
> > work at my side now.
>
> Ok
>
> > However, the same output without printk(), so the latencies here has
> > no effect.
> If printk() outputs to serial console it has a huge overhead. Further
> trace_printk() is designed to have very low overhead, even when compared to
> printk() not outputting to console.
Got it.
> [...]
>
> >> Yes, these timestamps are all over the place. It's due to the "big"
> >> gap of 100ms between the CAN frames. What's the configured bitrate of
> your bus?
> >
> > ip link set can0 up type can bitrate 1000000
>
> With 1Mbit/s you have overruns every 65ms (worst case).
Yes. What's the bitrate you want me have a test?
I have a question, mailbox read has taken counter overflow into consideration, why does overflow quite often will cause the frame disorder?
Best Regards,
Joakim Zhang
> Marc
>
> --
> Pengutronix e.K. | Marc Kleine-Budde |
> Embedded Linux | https://www.pengutronix.de |
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