> On Apr 6, 2016, at 4:53 PM, Peter Hurley <[email protected]> wrote: > > On 04/06/2016 02:56 PM, Rick Mann wrote: >> What would I need to get/do to enable me to single-step through >> kernel code on BBB/G? JTAG header, some kind of interface, and a >> bunch of software installed on Ubuntu? Can anyone make specific >> recommendations? Is it even possible? > > On 04/06/2016 03:34 PM, Rick Mann wrote: >> Thanks, John. I've tried printk and other logging, but it's virtually >> impossible to trace something like audio, which spans many modules. > > If this is a latency problem, ftrace is probably your best bet, but > function_graph and the other tracers can induce even more latency. My main purpose for using function_graph option was to understand program flow, so latency wasn’t an issue for me. I haven’t had any latency issues with my drivers, so I haven’t used the latency tracers that much. Mostly I use them to measure interrupt latency of the kernel. Other than that, my Lauterbach debugger gives me ns timing resolution in the trace buffer. > > I've had to write my own latency tracer on occasion to measure > specific code paths (most recently with UART DMA timeouts from > softirq latency). I cribbed the basic functionality from the > irqsoff tracer; let me know if that's something you'd find useful. > > If you really need to single-step, KGDB can be made to work but > there are some limitations, the most crucial being that kgdboc > runs over the console so you can't debug earlier than when the > built-in 8250 driver probes. That's like 3 secs into boot so lots > of init has already happened. I’m wondering if late init might work for the driver you want to debug? I haven’t tried this, but maybe this is a workaround for this issue. > > FWIW, I did push an earlycon OMAP bootconsole for v4.6 but -rc2 > is early days, and there's already been one problem with > MMC block device numbering. But if you're desperate and don't > have access to JTAG, earlycon does printk() output from even > before page table setup up to console initialization. > > Regards, > Peter Hurley > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout.
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