Re: Crash in msm serial on dragonboard with ftrace bootargs

[Sai Prakash Ranjan]

On 10/17/2018 2:21 AM, Stephen Boyd wrote:
> Quoting Sai Prakash Ranjan (2018-10-16 12:35:57)
> > On 10/17/2018 12:45 AM, Steven Rostedt wrote:
> > > On Wed, 17 Oct 2018 00:36:05 +0530
> > > Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx> wrote:
> > >
> > > > On 10/17/2018 12:33 AM, Steven Rostedt wrote:
> > > > > On Wed, 17 Oct 2018 00:31:03 +0530
> > > > > Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx> wrote:
> > > > >     
> > > > > > Haa seems like you are right! With "ftrace=function
> > > > > > ftrace_filter=msm_read" , I can trigger the crash, but
> > > > > > sadly "ftrace_notrace=msm_read" also crashes.
> > > > >
> > > > > So there's more than one problem area.
> > > > >
> > > > > What about ftrace_notrace=m*
> > > > >
> > > > > ?
> > > > >     
> > > >
> > > > That too crashes.
> > >
> > > Which compiler are you using and can you send me your config.
> > Config attached.
> >
> > Compiler: aarch64-linux-gnu-gcc (Linaro GCC 6.3-2017.02) 6.3.1 20170109
> >
> > > I wonder if there's something screwing up with the way ftrace nops are
> > > working on this board.
> > >
> > > A couple things of note, 1) it works fine after boot up. 2) it crashes
> > > in the initcall code, so it's not due to ftrace being enabled too early.
> > >
> > > I'd like to see the full command line as well. I bet if you remove the
> > > qcom,msm-uartdm from the command line, and had just ftrace=function, it
> > > may also boot fine too. Can you try that?
> >
> > Kernel command line: root=/dev/disk/by-partlabel/rootfs rw rootwait
> > ftrace=function ftrace_notrace=m* earlycon console=ttyMSM0,115200n8
> >
> > qcom,msm-uartdm is not in command line, it is the earlycon. So without
> > earlycon(bootconsole), board boots fine as we discussed earlier.
>
> Have you tried with earlycon and no ftrace things on the commandline?
>
>   root=/dev/disk/by-partlabel/rootfs rw rootwait earlycon console=ttyMSM0,115200n8
>
> If earlycon is causing problems, it sounds like this may be another case
> of earlycon uart handing off to the uart driver and that failing because
> something gets printed while the uart is transitioning from the earlycon
> console to the kernel boot console. I recall the uart would trample on
> itself in interesting ways.

Yes I have tried with only earlycon enabled and everything is fine. 
Issue is reproduced only with ftrace=function cmdline.

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