[PATCH 1/9] media: rzg2l-cru: Add device_link from CRU to CSI-2

[Tommaso Merciai]

The CRU device depends on CSI-2 to operate. Without an explicit
device_link the PM core has no knowledge of this dependency and may
suspend CSI-2 while CRU is still active, or resume CRU before CSI-2
is ready.

Add a DL_FLAG_STATELESS device_link from the CRU to CSI-2 when the
CSI-2 subdev binds. This instructs the PM core to suspend CRU before
CSI-2 and to resume CSI-2 before CRU. The link is deleted on unbind.

Signed-off-by: Tommaso Merciai <tommaso.merciai.xr@xxxxxxxxxxxxxx>
---
 drivers/media/platform/renesas/rzg2l-cru/rzg2l-core.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-core.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-core.c
index 3c5fbd857371..1b12d91eaec9 100644
--- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-core.c
+++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-core.c
@@ -101,6 +101,7 @@ static void rzg2l_cru_group_notify_unbind(struct v4l2_async_notifier *notifier,
 	mutex_lock(&cru->mdev_lock);
 
 	if (cru->csi.asd == asd) {
+		device_link_remove(cru->dev, subdev->dev);
 		cru->csi.subdev = NULL;
 		dev_dbg(cru->dev, "Unbind CSI-2 %s\n", subdev->name);
 	}
@@ -118,6 +119,12 @@ static int rzg2l_cru_group_notify_bound(struct v4l2_async_notifier *notifier,
 
 	if (cru->csi.asd == asd) {
 		cru->csi.subdev = subdev;
+		if (!device_link_add(cru->dev, subdev->dev, DL_FLAG_STATELESS)) {
+			dev_err(cru->dev, "Failed to create device link to CSI-2 %s\n",
+				subdev->name);
+			mutex_unlock(&cru->mdev_lock);
+			return -EINVAL;
+		}
 		dev_dbg(cru->dev, "Bound CSI-2 %s\n", subdev->name);
 	}
 
-- 
2.54.0