linux-kernel - Re: [PATCH] coresight: etm4x: Skip setting LPOVERRIDE bit for qcom,skip-power-up

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Date:   Fri, 16 Oct 2020 17:17:09 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Suzuki Poulose <suzuki.poulose@....com>
Cc:     Mathieu Poirier <mathieu.poirier@...aro.org>,
        Mike Leach <mike.leach@...aro.org>, coresight@...ts.linaro.org,
        Stephen Boyd <swboyd@...omium.org>, denik@...omium.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] coresight: etm4x: Skip setting LPOVERRIDE bit for
 qcom,skip-power-up

Hi Suzuki,

On 2020-10-16 16:51, Suzuki Poulose wrote:
> Hi Sai,
> 
> On 10/16/20 11:10 AM, Sai Prakash Ranjan wrote:
>> There is a bug on the systems supporting to skip power up
>> (qcom,skip-power-up) where setting LPOVERRIDE bit(low-power
>> state override behaviour) will result in CPU hangs/lockups
>> even on the implementations which supports it. So skip
>> setting the LPOVERRIDE bit for such platforms.
>> 
>> Fixes: 02510a5aa78d ("coresight: etm4x: Add support to skip trace unit 
>> power up")
>> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
> 
> The fix is fine by me. Btw, is there a hardware Erratum assigned for
> this ? It would be good to have the Erratum documented somewhere,
> preferrably ( Documentation/arm64/silicon-errata.rst )
> 

No, afaik we don't have any erratum assigned to this bug.
It was already present in downstream kernel and since we
support these targets with the previous HW bug
(qcom,skip-power-up) now in upstream, we would need this
fix in upstream kernel as well.

Thanks,
Sai

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