linux-kernel - Re: [PATCH V4 01/11] coresight: etm4x: Fix unbalanced pm_runtime

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Message-ID: <68eb9e4e-de77-4854-8212-816c66d5f657@arm.com>
Date: Thu, 15 Feb 2024 11:04:04 +0000
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Anshuman Khandual <anshuman.khandual@....com>,
 linux-arm-kernel@...ts.infradead.org
Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Sudeep Holla <sudeep.holla@....com>, Mike Leach <mike.leach@...aro.org>,
 James Clark <james.clark@....com>,
 Maxime Coquelin <mcoquelin.stm32@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>, linux-acpi@...r.kernel.org,
 linux-kernel@...r.kernel.org, coresight@...ts.linaro.org,
 linux-stm32@...md-mailman.stormreply.com, Hanjun Guo <guohanjun@...wei.com>,
 "Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>,
 Leo Yan <leo.yan@...aro.org>
Subject: Re: [PATCH V4 01/11] coresight: etm4x: Fix unbalanced
 pm_runtime_enable()

On 23/01/2024 05:45, Anshuman Khandual wrote:
> There is an unbalanced pm_runtime_enable() in etm4_probe_platform_dev()
> when etm4_probe() fails. This problem can be observed via the coresight
> etm4 module's (load -> unload -> load) sequence when etm4_probe() fails
> in etm4_probe_platform_dev().
> 
> [   63.379943] coresight-etm4x 7040000.etm: Unbalanced pm_runtime_enable!
> [   63.393630] coresight-etm4x 7140000.etm: Unbalanced pm_runtime_enable!
> [   63.407455] coresight-etm4x 7240000.etm: Unbalanced pm_runtime_enable!
> [   63.420983] coresight-etm4x 7340000.etm: Unbalanced pm_runtime_enable!
> [   63.420999] coresight-etm4x 7440000.etm: Unbalanced pm_runtime_enable!
> [   63.441209] coresight-etm4x 7540000.etm: Unbalanced pm_runtime_enable!
> [   63.454689] coresight-etm4x 7640000.etm: Unbalanced pm_runtime_enable!
> [   63.474982] coresight-etm4x 7740000.etm: Unbalanced pm_runtime_enable!
> 
> This fixes the above problem - with an explicit pm_runtime_disable() call
> when etm4_probe() fails during etm4_probe_platform_dev().

Fixes: 5214b563588e ("coresight: etm4x: Add support for sysreg only devices"

> 
> Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>
> Cc: Hanjun Guo <guohanjun@...wei.com>
> Cc: Sudeep Holla <sudeep.holla@....com>
> Cc: "Rafael J. Wysocki" <rafael@...nel.org>
> Cc: Len Brown <lenb@...nel.org>
> Cc: Suzuki K Poulose <suzuki.poulose@....com>
> Cc: Mike Leach <mike.leach@...aro.org>
> Cc: James Clark <james.clark@....com>
> Cc: Leo Yan <leo.yan@...aro.org>
> Cc: linux-acpi@...r.kernel.org
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> Cc: coresight@...ts.linaro.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
> Changes in V4:
> 
> - New patch in the series
> 
>   drivers/hwtracing/coresight/coresight-etm4x-core.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> index ce1995a2827f..7c693b45ac05 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> @@ -2217,6 +2217,9 @@ static int etm4_probe_platform_dev(struct platform_device *pdev)
>   	ret = etm4_probe(&pdev->dev);
>   
>   	pm_runtime_put(&pdev->dev);
> +	if (ret)
> +		pm_runtime_disable(&pdev->dev);
> +
>   	return ret;
>   }
>   

Looks good to me. I have glanced through the other platform device 
driver code in coresight subsystem and they all seem to be safe, except
for Ultrasoc-smb, which doesn't do any power managment. It may be, 
because it is only supported on an ACPI system.

Suzuki