[ Upstream commit c45b2835e7b205783bdfe08cc98fa86a7c5eeb74 ]
child_fwnode should be a read only property based on the DT or ACPI. If
it's 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: 37ea1ffddf ("coresight: Use fwnode handle instead of device names")
Fixes: 2af89ebacf ("coresight: Clear the connection field properly")
Tested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Mike Leach <mike.leach@linaro.org>
Signed-off-by: James Clark <james.clark@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20230425143542.2305069-2-james.clark@arm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
6d702c7a22