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coresight: Fix loss of connection info when a module is unloaded

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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
This commit is contained in:
James Clark 2023-04-25 15:35:28 +01:00 committed by Suzuki K Poulose
parent d388f06ace
commit c45b2835e7
1 changed files with 2 additions and 7 deletions
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9
drivers/hwtracing/coresight/coresight-core.c
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@ -1419,13 +1419,8 @@ static int coresight_remove_match(struct device *dev, void *data)
if (csdev->dev.fwnode == conn->child_fwnode) {
iterator->orphan = true;
coresight_remove_links(iterator, conn);
/*
* Drop the reference to the handle for the remote
* device acquired in parsing the connections from
* platform data.
*/
fwnode_handle_put(conn->child_fwnode);
conn->child_fwnode = NULL;
conn->child_dev = NULL;
/* No need to continue */
break;
}