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Message-ID: <8cb0be8c-8ff2-d643-2dba-135974c8bc3b@arm.com>
Date:   Tue, 4 Apr 2023 15:02:19 +0100
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Subject: Re: [PATCH v4 01/13] coresight: Fix loss of connection info when a
 module is unloaded
To:     James Clark <james.clark@arm.com>, coresight@lists.linaro.org,
        quic_jinlmao@quicinc.com, mike.leach@linaro.org
Cc:     Mathieu Poirier <mathieu.poirier@linaro.org>,
        Leo Yan <leo.yan@linaro.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20230404135401.1728919-1-james.clark@arm.com>
 <20230404135401.1728919-2-james.clark@arm.com>
From:   Suzuki K Poulose <suzuki.poulose@arm.com>
In-Reply-To: <20230404135401.1728919-2-james.clark@arm.com>
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On 04/04/2023 14:53, James Clark wrote:
> child_fwnode should be a read only property based on the DT. If it's

minor nit: Not restricted to DT. This also covers the ACPI.

> cleared on the parent device when a child is unloaded, then when the
> child is loaded again the connection won't be remade.
> 
> child_dev should be cleared instead which signifies that the connection
> should be remade when the child_fwnode registers a new coresight_device.
> 
> Similarly the reference count shouldn't be decremented as long as the
> parent device exists. The correct place to drop the reference is in
> coresight_release_platform_data() which is already done.
> 
> Reproducible on Juno with the following steps:
> 
>    # load all coresight modules.
>    $ cd /sys/bus/coresight/devices/
>    $ echo 1 > tmc_etr0/enable_sink
>    $ echo 1 > etm0/enable_source
>    # Works fine ^
> 
>    $ echo 0 > etm0/enable_source
>    $ rmmod coresight-funnel
>    $ modprobe coresight-funnel
>    $ echo 1 > etm0/enable_source
>    -bash: echo: write error: Invalid argument
> 
> Fixes: 37ea1ffddffa ("coresight: Use fwnode handle instead of device names")
> Fixes: 2af89ebacf29 ("coresight: Clear the connection field properly")
> Signed-off-by: James Clark <james.clark@arm.com>

Looks good to me.

Tested-by: Suzuki K Poulose <suzuki.poulose@arm.com>