linux-kernel - Re: [PATCH] coresight: cti: Fix hang in cti_disable

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Message-ID: <61b38606-8006-30c3-d94c-8bc5e4f38bf7@arm.com>
Date:   Wed, 19 Oct 2022 15:51:22 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     James Clark <james.clark@....com>, coresight@...ts.linaro.org
Cc:     mathieu.poirier@...aro.org, mike.leach@...aro.org,
        leo.yan@...aro.org, Sudeep.Holla@....com,
        Aishwarya TCV <Aishwarya.TCV@....com>,
        Cristian Marussi <Cristian.Marussi@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] coresight: cti: Fix hang in cti_disable_hw()

Hi James

On 05/10/2022 14:14, James Clark wrote:
> cti_enable_hw() and cti_disable_hw() are called from an atomic context
> so shouldn't use runtime PM because it can result in a sleep when
> communicating with firmware.
> 
> Since commit 3c6656337852 ("Revert "firmware: arm_scmi: Add clock
> management to the SCMI power domain""), this causes a hang on Juno when
> running the Perf Coresight tests or running this command:
> 
>    perf record -e cs_etm//u -- ls
> 
> This was also missed until the revert commit because pm_runtime_put()
> was called with the wrong device until commit 692c9a499b28 ("coresight:
> cti: Correct the parameter for pm_runtime_put")
> 
> With lock and scheduler debugging enabled the following is output:
> 

...

> 
> Fix the issue by removing the runtime PM calls completely. They are not
> needed here because it must have already been done when building the
> path for a trace.
> 
> Fixes: 835d722ba10a ("coresight: cti: Initial CoreSight CTI Driver")
> Reported-by: Aishwarya TCV <Aishwarya.TCV@....com>
> Reported-by: Cristian Marussi <Cristian.Marussi@....com>
> Signed-off-by: Suzuki Poulose <Suzuki.Poulose@....com>

I have applied this patch, changing the above to:

Suggested-by: ...

Suzuki