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SubjectRe: [PATCH v3 06/13] coresight: Fix loss of connection info when a module is unloaded
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Hi James

On 29/03/2023 12:53, James Clark wrote:
> child_fwnode should be a read only property based on the DT. 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.
>
> Signed-off-by: James Clark <james.clark@arm.com>

This looks like a bug in the existing driver. Please could you keep this
at the beginning of the series, so that it is easier to backport for
stable ?

Also, please add :

Fixes: 37ea1ffddffa ("coresight: Use fwnode handle instead of device names")
Fixes: 2af89ebacf29 ("coresight: Clear the connection field properly")


> ---
> drivers/hwtracing/coresight/coresight-core.c | 10 ++--------
> 1 file changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
> index bfe1b93aca4e..12cbb68e8e1c 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -1414,13 +1414,8 @@ static int coresight_remove_match(struct device *dev, void *data)
> if (csdev->dev.fwnode == conn->dest_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->dest_fwnode);
> - conn->dest_fwnode = NULL;
> +
> + conn->dest_dev = NULL;
> /* No need to continue */
> break;
> }
> @@ -1553,7 +1548,6 @@ void coresight_release_platform_data(struct coresight_device *csdev,
> * is going away
> */
> fwnode_handle_put(conns[i].dest_fwnode);
> - pdata->out_conns[i].dest_fwnode = NULL;

This change is not required, as we are freeing the pdata anyway.
Keeping this might be beneficial if someone else comes looking
for references while we are going out. I don't see how we could
hit that, but just to be safe.

Suzuki

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