Hi Steve,
Thanks for your patch, I think it looks good.
On 2019-01-06 13:20:18 -0800, Steve Longerbeam wrote:
> There is a block of code in rvin_group_link_notify() that loops through
> all entities in the media graph, and prevents enabling a link to a VIN
> node if any entity is in use. This prevents enabling a VIN link even if
> there is an in-use entity somewhere in the graph that is independent of
> the link's pipeline.
>
> For example, the code will prevent enabling a link from the first
> rcar-csi2 receiver to a VIN node even if there is an enabled link
> somewhere far upstream on the second independent rcar-csi2 receiver
> pipeline.
>
> If this code is meant to prevent modifying a link if any entity in the
> graph is actively involved in streaming (because modifying the CHSEL
> register fields can disrupt any/all running streams), then the entities
> stream counts should be checked rather than the use counts.
>
> (There is already such a check in __media_entity_setup_link() that verifies
> the stream_count of the link's source and sink entities are both zero,
> but that is insufficient, since there should be no running streams in
> the entire graph).
>
> Modify the media_device_for_each_entity() loop to check the entity
> stream_count instead of the use_count, and elaborate on the comment.
> VIN node links can now be enabled even if there are other independent
> in-use entities that are not streaming.
>
> Fixes: c0cc5aef31 ("media: rcar-vin: add link notify for Gen3")
>
> Signed-off-by: Steve Longerbeam <slongerbeam@xxxxxxxxx>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@xxxxxxxxxxxx>
> ---
> Changes in v2:
> - bring back the media_device_for_each_entity() loop but check the
> stream_count not the use_count.
> ---
> drivers/media/platform/rcar-vin/rcar-core.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/platform/rcar-vin/rcar-core.c b/drivers/media/platform/rcar-vin/rcar-core.c
> index f0719ce24b97..6dd6b11c1b2b 100644
> --- a/drivers/media/platform/rcar-vin/rcar-core.c
> +++ b/drivers/media/platform/rcar-vin/rcar-core.c
> @@ -131,9 +131,13 @@ static int rvin_group_link_notify(struct media_link *link, u32 flags,
> !is_media_entity_v4l2_video_device(link->sink->entity))
> return 0;
>
> - /* If any entity is in use don't allow link changes. */
> + /*
> + * Don't allow link changes if any entity in the graph is
> + * streaming, because modifying the CHSEL register fields
> + * can disrupt running streams.
> + */
> media_device_for_each_entity(entity, &group->mdev)
> - if (entity->use_count)
> + if (entity->stream_count)
> return -EBUSY;
>
> mutex_lock(&group->lock);
> --
> 2.17.1
>
--
Regards,
Niklas Söderlund
