[PATCH v4 01/13] coresight: Fix loss of connection info when a module is unloaded

[Suzuki K Poulose]

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 at arm.com>

Looks good to me.

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