linux-kernel - Re: [PATCHv9 2/3] arm64: dts: qcom: msm8998: Add Coresight support

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Date:   Tue, 01 Oct 2019 10:52:15 -0700
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Jeffrey Hugo <jeffrey.l.hugo@...il.com>
Cc:     Mark Rutland <mark.rutland@....com>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        MSM <linux-arm-msm@...r.kernel.org>,
        Marc Gonzalez <marc.w.gonzalez@...e.fr>,
        lkml <linux-kernel@...r.kernel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Sibi Sankar <sibis@...eaurora.org>,
        Leo Yan <leo.yan@...aro.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCHv9 2/3] arm64: dts: qcom: msm8998: Add Coresight support

On 2019-10-01 10:14, Jeffrey Hugo wrote:
> On Tue, Oct 1, 2019 at 11:04 AM Sai Prakash Ranjan
> <saiprakash.ranjan@...eaurora.org> wrote:
>> 
>> On 2019-10-01 09:13, Jeffrey Hugo wrote:
>> > Sai,
>> >
>> > This patch breaks boot on the 835 laptops.  However, I haven't seen
>> > the same issue on the MTP.  I wonder, is coresight expected to work
>> > with production fused devices?  I wonder if thats the difference
>> > between the laptop and MTP that is causing the issue.
>> >
>> > Let me know what I can do to help debug.
>> >
>> 
>> I did test on MSM8998 MTP and didn't face any issue. I am guessing 
>> this
>> is the same issue which you reported regarding cpuidle? Coresight ETM
> 
> Yes, its the same issue.  Right now, I need both patches reverted to 
> boot.
> 
>> and cpuidle do not work well together since ETMs share the same power
>> domain as CPU and they might get turned off when CPU enters idle 
>> states.
>> Can you try with cpuidle.off=1 cmdline or just remove idle states from
>> DT to confirm? If this is the issue, then we can try the below patch
>> from Andrew Murray for ETM save and restore:
>> 
>> https://patchwork.kernel.org/patch/11097893/
> 
> Is there still value in testing this if the idle states are removed,
> yet the coresight nodes still cause issues?
> 
> Funny enough, I'm using the arm64 defconfig which doesn't seem to
> select CONFIG_CORESIGHT, so I'm not even sure what would be binding to
> the DT devices...
> 

Haan then likely it's the firmware issue.
We should probably disable coresight in soc dtsi and enable only for 
MTP. For now you can add a status=disabled for all coresight nodes in 
msm8998.dtsi and I will send the patch doing the same in a day or 
two(sorry I am travelling currently).

Thanks,
Sai