On 11/11/19 12:32 PM, Joakim Zhang wrote:
> echo 1 > /sys/kernel/debug/tracing/tracing_on
>
> trace_printk("\nmailbox_num = %u, timestamp = %u, can_id = %x\n", n,
> timestamp, cfd->can_id); Add in mailbox_read(), but is print
> nothing, could you give me some guidance?
I think you need CONFIG_TRACING enabled in you .config.
> I always use printk() to debug, but I think it cannot print until
> suspend exit totally, so dump mailbox num, timestamp, and can id
> failed before.
Try to add a trace_printk() to the probe function. Your kernel should
spit out a big warning message on the first usage:
> Nov 11 12:34:49 orangebox kernel: **********************************************************
> Nov 11 12:34:49 orangebox kernel: ** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **
> Nov 11 12:34:50 orangebox kernel: ** **
> Nov 11 12:34:50 orangebox kernel: ** trace_printk() being used. Allocating extra memory. **
> Nov 11 12:34:50 orangebox kernel: ** **
> Nov 11 12:34:50 orangebox kernel: ** This means that this is a DEBUG kernel and it is **
> Nov 11 12:34:50 orangebox kernel: ** unsafe for production use. **
> Nov 11 12:34:50 orangebox kernel: ** **
> Nov 11 12:34:50 orangebox kernel: ** If you see this message and you are not debugging **
> Nov 11 12:34:50 orangebox kernel: ** the kernel, report this immediately to your vendor! **
> Nov 11 12:34:50 orangebox kernel: ** **
> Nov 11 12:34:50 orangebox kernel: ** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **
> Nov 11 12:34:50 orangebox kernel: **********************************************************
Then have a look at the trace file:
> pi@orangebox:~ $ sudo cat /sys/kernel/debug/tracing/trace
> # tracer: nop
> #
> # entries-in-buffer/entries-written: 1/1 #P:4
> #
> # _-----=> irqs-off
> # / _----=> need-resched
> # | / _---=> hardirq/softirq
> # || / _--=> preempt-depth
> # ||| / delay
> # TASK-PID CPU# |||| TIMESTAMP FUNCTION
> # | | | |||| | |
> modprobe-230 [001] .... 7.425339: mcp25xxfd_probe: mcp25xxfd_probe: foo
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
Vertretung West/Dortmund | Phone: +49-231-2826-924 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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