[PATCH v2 0/1] media: imx: csi: Parse link configuration from fw_node

[PATCH v2 0/1] media: imx: csi: Parse link configuration from fw_node

[Mathis Foerst]

Hi,

this patch fixes the imx-media-csi driver to work with camera drivers that
do not implement the subdev-pad-operation "get_mbus_format".

Changelog:
v1 -> v2:
- Factor out the function "csi_parse_upstream_fw_link_config" for better
readability.

It's the follow up of this discussion:
https://lore.kernel.org/linux-media/Z8AoA6WjbXQufqR6@kekkonen.localdomain/

I tested the changes successfully on an i.MX6DL with an MT9M114 and an
MT9V032 camera. They both use the parallel camera interface.
Sadly, I don't have the hardware to test with a MIPI CSI-2 camera.

Best regards,
Mathis Foerst


Mathis Foerst (1):
  media: imx: csi: Parse link configuration from fw_node

 drivers/staging/media/imx/imx-media-csi.c | 36 ++++++++++++++++++++---
 1 file changed, 32 insertions(+), 4 deletions(-)


base-commit: ac9c34d1e45a4c25174ced4fc0cfc33ff3ed08c7
-- 
2.34.1

[PATCH v2 1/1] media: imx: csi: Parse link configuration from fw_node

[Mathis Foerst]

The imx-media-csi driver requires upstream camera drivers to implement
the subdev-pad-op "get_mbus_config" [0]. Camera drivers that don't
implement this function are not usable on the i.MX6.

The docs for get_mbus_config [1] say:
@get_mbus_config: get the media bus configuration of a remote sub-device.
            The media bus configuration is usually retrieved from the
            firmware interface at sub-device probe time, immediately
            applied to the hardware and eventually adjusted by the
            driver.

Currently, the imx-media-csi driver is not incorporating the information
from the firmware interface and therefore relies on the implementation of
get_mbus_config by the camera driver.

To be compatible with camera drivers not implementing get_mbus_config
(which is the usual case), use the bus information from the fw interface:

The camera does not necessarily has a direct media bus link to the CSI as
the video-mux and/or the MIPI CSI-2 receiver of the i.MX6 might be in
between them on the media pipeline.
The CSI driver already implements the functionality to find the connected
camera sub-device to call get_mbus_config on it.

At this point the driver is modified as follows:
In the case that get_mbus_config is not implemented by the upstream
camera, try to get its endpoint configuration from the firmware interface
usign v4l2_fwnode_endpoint_parse.
For the supported mbus_types (V4L2_MBUS_PARALLEL, V4L2_MBUS_BT656 and
V4L2_MBUS_CSI2_DPHY), extract the mbus_config from the endpoint
configuration.
For all other mbus_types, return an error.

Note that parsing the mbus_config from the fw interface is not done during
probing because the camera that's connected to the CSI can change based on
the selected input of the video-mux at runtime.

[0] drivers/staging/media/imx/imx-media-csi.c - line 211..216
[1] include/media/v4l2-subdev.h - line 814

Signed-off-by: Mathis Foerst <mathis.foerst@mt.com>
---
 drivers/staging/media/imx/imx-media-csi.c | 36 ++++++++++++++++++++---
 1 file changed, 32 insertions(+), 4 deletions(-)

diff --git a/drivers/staging/media/imx/imx-media-csi.c b/drivers/staging/media/imx/imx-media-csi.c
index 3edbc57be2ca..394a9321a10b 100644
--- a/drivers/staging/media/imx/imx-media-csi.c
+++ b/drivers/staging/media/imx/imx-media-csi.c
@@ -169,6 +169,8 @@ static int csi_get_upstream_mbus_config(struct csi_priv *priv,
 {
 	struct v4l2_subdev *sd, *remote_sd;
 	struct media_pad *remote_pad;
+	struct fwnode_handle *ep_node;
+	struct v4l2_fwnode_endpoint ep = { .bus_type = 0 };
 	int ret;
 
 	if (!priv->src_sd)
@@ -210,11 +212,37 @@ static int csi_get_upstream_mbus_config(struct csi_priv *priv,
 
 	ret = v4l2_subdev_call(remote_sd, pad, get_mbus_config,
 			       remote_pad->index, mbus_cfg);
-	if (ret == -ENOIOCTLCMD)
-		v4l2_err(&priv->sd,
-			 "entity %s does not implement get_mbus_config()\n",
-			 remote_pad->entity->name);
+	if (ret == -ENOIOCTLCMD) {
+		/*
+		 * If the upstream sd does not implement get_mbus_config,
+		 * try to parse the link configuration from its fw_node
+		 */
+		ep_node = fwnode_graph_get_endpoint_by_id(dev_fwnode(remote_sd->dev),
+							  0, 0,
+							  FWNODE_GRAPH_ENDPOINT_NEXT);
+		if (!ep_node)
+			return -ENOTCONN;
+
+		ret = v4l2_fwnode_endpoint_parse(ep_node, &ep);
+		fwnode_handle_put(ep_node);
+		if (ret)
+			return ret;
 
+		mbus_cfg->type = ep.bus_type;
+		switch (ep.bus_type) {
+		case V4L2_MBUS_PARALLEL:
+		case V4L2_MBUS_BT656:
+			mbus_cfg->bus.parallel = ep.bus.parallel;
+			break;
+		case V4L2_MBUS_CSI2_DPHY:
+			mbus_cfg->bus.mipi_csi2 = ep.bus.mipi_csi2;
+			break;
+		default:
+			v4l2_err(&priv->sd, "Unsupported mbus_type: %i\n",
+				 ep.bus_type);
+			return -EINVAL;
+		}
+	}
 	return ret;
 }
 
-- 
2.34.1