On 1/9/19 2:40 PM, Niklas Söderlund wrote:
Hi Steve,
Thanks for your patch, I think it looks good.
Thanks for the Ack! I'm not real familiar with the RFC patch process.
Should this be submitted again with RFC stripped from the subject line?
Steve
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
