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Subject: Re: Crash in msm serial on dragonboard with ftrace bootargs
To:     Stephen Boyd <sboyd@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>
Cc:     Bjorn Andersson <bjorn.andersson@linaro.org>,
        Andy Gross <andy.gross@linaro.org>,
        David Brown <david.brown@linaro.org>,
        Jiri Slaby <jslaby@suse.com>,
        Kees Cook <keescook@chromium.org>,
        "Joel Fernandes (Google)" <joel@joelfernandes.org>,
        Geliang Tang <geliangtang@gmail.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Pramod Gurav <gpramod@codeaurora.org>,
        linux-arm-msm@vger.kernel.org, linux-soc@vger.kernel.org,
        linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
        Rajendra Nayak <rnayak@codeaurora.org>,
        Vivek Gautam <vivek.gautam@codeaurora.org>,
        Sibi Sankar <sibis@codeaurora.org>
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From:   Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Message-ID: <17116a6b-156e-af2f-c20c-88bea10bfc92@codeaurora.org>
Date:   Wed, 17 Oct 2018 16:57:42 +0530
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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@codeaurora.org> 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@codeaurora.org> 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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