Re: [PATCH V4 01/11] coresight: etm4x: Fix unbalanced pm_runtime_enable()

[Suzuki K Poulose <suzuki.poulose@arm.com>]

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@kernel.org>
> Cc: Hanjun Guo <guohanjun@huawei.com>
> Cc: Sudeep Holla <sudeep.holla@arm.com>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Cc: Len Brown <lenb@kernel.org>
> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
> Cc: Mike Leach <mike.leach@linaro.org>
> Cc: James Clark <james.clark@arm.com>
> Cc: Leo Yan <leo.yan@linaro.org>
> Cc: linux-acpi@vger.kernel.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Cc: coresight@lists.linaro.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.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