[PATCH 6.4 602/800] coresight: Fix loss of connection info when a module is unloaded

Greg Kroah-Hartman
2023-07-16T20:20:59Z

From: James Clark <james.clark@arm.com>

[ 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: 37ea1ffddffa ("coresight: Use fwnode handle instead of device names")
Fixes: 2af89ebacf29 ("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>
---
drivers/hwtracing/coresight/coresight-core.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index d3bf82c0de1d8..5733294ce5cd2 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -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;
}
--
2.39.2