On Mon, Jan 11, 2021 at 02:59:59PM +0200, Mikko Perttunen wrote:
> To avoid false lockdep warnings, give each client lock a different
> lock class, passed from the initialization site by macro.
> 
> Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
> ---
>  drivers/gpu/host1x/bus.c | 7 ++++---
>  include/linux/host1x.h   | 9 ++++++++-
>  2 files changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/host1x/bus.c b/drivers/gpu/host1x/bus.c
> index 347fb962b6c9..8fc79e9cb652 100644
> --- a/drivers/gpu/host1x/bus.c
> +++ b/drivers/gpu/host1x/bus.c
> @@ -715,13 +715,14 @@ EXPORT_SYMBOL(host1x_driver_unregister);
>   * device and call host1x_device_init(), which will in turn call each client's
>   * &host1x_client_ops.init implementation.
>   */
> -int host1x_client_register(struct host1x_client *client)
> +int __host1x_client_register(struct host1x_client *client,
> +			   struct lock_class_key *key)

I've seen the kbuild robot warn about this because the kerneldoc is now
out of date.

>  {
>  	struct host1x *host1x;
>  	int err;
>  
>  	INIT_LIST_HEAD(&client->list);
> -	mutex_init(&client->lock);
> +	__mutex_init(&client->lock, "host1x client lock", key);

Should we maybe attempt to make this unique? Could we use something like
dev_name(client->dev) for this?

Thierry