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

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Date:   Tue, 01 Oct 2019 10:04:14 -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>,
        Vivek Gautam <vivek.gautam@...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 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 
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/

It is not merged yet. They would appreciate your tested by ;)

Thanks,
Sai