[PATCH v2 0/3] media: imx-mipi-csis: Get the number of active lanes from mbus_config

[PATCH v2 0/3] media: imx-mipi-csis: Get the number of active lanes from mbus_config

[Isaac Scott]

It is possible that the number of desired active MIPI CSI2 data lanes
does not match the maximum listed in device tree. Add a helper function
to v4l2_common that calls the get_mbus_config op to get the number of
actively used data lanes in drivers that support it.

Compare it to the number of lanes configured in device tree, and if its
invalid, use the number present in device tree.

This series also uses the helper in imx-mipi-csis driver to set the
currently configured num_data_lanes, while keeping track of the number
of data lanes set in device tree to ensure we can still use all possible
lanes if we need to, and the upstream subdev driver requests them.

Tested on v6.15, compile tested on v6.17-rc4.

---------

Changes v1 -> v2:

- Added helper function to get active data lanes in v4l2-common
- Store the maximum data lanes possible, as configured in device tree
- Added media: prefix to commit titles

Isaac Scott (3):
  media: v4l: Add helper to get number of active lanes via a pad
  media: imx-mipi-csis: Store the number of data_lanes configured in dt
  media: imx-mipi-csis: Get number of active lanes via mbus_config

 drivers/media/platform/nxp/imx-mipi-csis.c |  8 ++++++-
 drivers/media/v4l2-core/v4l2-common.c      | 25 ++++++++++++++++++++++
 include/media/v4l2-common.h                |  1 +
 3 files changed, 33 insertions(+), 1 deletion(-)

-- 
2.43.0

[PATCH v2 1/3] media: v4l: Add helper to get number of active lanes via a pad

[Isaac Scott]

Sometimes, users will not use all of the MIPI CSI 2 lanes available when
connecting to the MIPI CSI receiver of their device. Add a helper
function that checks the mbus_config for the device driver to allow
users to define the number of active data lanes through the
get_mbus_config op.

If the driver does not implement this op, fall back to using the number
of data lanes specified in device tree.

Signed-off-by: Isaac Scott <isaac.scott@ideasonboard.com>
---
 drivers/media/v4l2-core/v4l2-common.c | 25 +++++++++++++++++++++++++
 include/media/v4l2-common.h           |  1 +
 2 files changed, 26 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c
index 6e585bc76367..8683107b3704 100644
--- a/drivers/media/v4l2-core/v4l2-common.c
+++ b/drivers/media/v4l2-core/v4l2-common.c
@@ -571,6 +571,31 @@ s64 __v4l2_get_link_freq_pad(struct media_pad *pad, unsigned int mul,
 	return __v4l2_get_link_freq_ctrl(sd->ctrl_handler, mul, div);
 }
 EXPORT_SYMBOL_GPL(__v4l2_get_link_freq_pad);
+
+unsigned int v4l2_get_active_data_lanes(const struct media_pad *pad, unsigned int dt_lanes)
+{
+	struct v4l2_mbus_config mbus_config = {};
+	struct v4l2_subdev *sd;
+	unsigned int lanes;
+	int ret;
+
+	sd = media_entity_to_v4l2_subdev(pad->entity);
+	ret = v4l2_subdev_call(sd, pad, get_mbus_config, pad->index,
+			       &mbus_config);
+	if (ret < 0 && ret != -ENOIOCTLCMD)
+		return ret;
+
+	if (!mbus_config.bus.mipi_csi2.num_data_lanes)
+		return dt_lanes;
+
+	lanes = mbus_config.bus.mipi_csi2.num_data_lanes;
+
+	if (lanes < 0 || lanes > dt_lanes)
+		return -EINVAL;
+
+	return lanes;
+}
+EXPORT_SYMBOL_GPL(v4l2_get_active_data_lanes);
 #endif /* CONFIG_MEDIA_CONTROLLER */
 
 /*
diff --git a/include/media/v4l2-common.h b/include/media/v4l2-common.h
index 0a43f56578bc..3f8937260c76 100644
--- a/include/media/v4l2-common.h
+++ b/include/media/v4l2-common.h
@@ -584,6 +584,7 @@ int v4l2_fill_pixfmt_mp(struct v4l2_pix_format_mplane *pixfmt, u32 pixelformat,
 	(pad, mul, div)
 s64 __v4l2_get_link_freq_pad(struct media_pad *pad, unsigned int mul,
 			     unsigned int div);
+unsigned int v4l2_get_active_data_lanes(const struct media_pad *pad, unsigned int dt_lanes);
 #else
 #define v4l2_get_link_freq(handler, mul, div)		\
 	__v4l2_get_link_freq_ctrl(handler, mul, div)
-- 
2.43.0

[PATCH v2 2/3] media: imx-mipi-csis: Store the number of data_lanes configured in dt

[Isaac Scott]

The number of lanes actively used by a MIPI CSI transmitter may differ
from that which is defined in device tree. To allow us to be able to set
the number of configured lanes without changing the maximum lane count,
store the number of lanes configured in device tree, and adjust the
debug print to reflect the device tree value.

Signed-off-by: Isaac Scott <isaac.scott@ideasonboard.com>
---
 drivers/media/platform/nxp/imx-mipi-csis.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/nxp/imx-mipi-csis.c b/drivers/media/platform/nxp/imx-mipi-csis.c
index 2beb5f43c2c0..fc89325f2f94 100644
--- a/drivers/media/platform/nxp/imx-mipi-csis.c
+++ b/drivers/media/platform/nxp/imx-mipi-csis.c
@@ -313,6 +313,8 @@ struct mipi_csis_device {
 	u32 hs_settle;
 	u32 clk_settle;
 
+	unsigned int max_data_lanes;
+
 	spinlock_t slock;	/* Protect events */
 	struct mipi_csis_event events[MIPI_CSIS_NUM_EVENTS];
 	struct dentry *debugfs_root;
@@ -1299,8 +1301,9 @@ static int mipi_csis_async_register(struct mipi_csis_device *csis)
 	}
 
 	csis->bus = vep.bus.mipi_csi2;
+	csis->max_data_lanes = vep.bus.mipi_csi2.num_data_lanes;
 
-	dev_dbg(csis->dev, "data lanes: %d\n", csis->bus.num_data_lanes);
+	dev_dbg(csis->dev, "data lanes: %d\n", csis->max_data_lanes);
 	dev_dbg(csis->dev, "flags: 0x%08x\n", csis->bus.flags);
 
 	asd = v4l2_async_nf_add_fwnode_remote(&csis->notifier, ep,
-- 
2.43.0

[PATCH v2 3/3] media: imx-mipi-csis: Get number of active lanes via mbus_config

[Isaac Scott]

The number of lanes actively used by a MIPI CSI transmitter may differ
from that which is defined in device tree. As such, call on
v4l2_get_active_data_lanes to check if the driver reports a
differing number of lanes to device tree, and use that number of active
lanes.

If the number of active data lanes is invalid, or the op is not
supported, it will use the number of lanes defined in device tree.

Signed-off-by: Isaac Scott <isaac.scott@ideasonboard.com>
---
 drivers/media/platform/nxp/imx-mipi-csis.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/media/platform/nxp/imx-mipi-csis.c b/drivers/media/platform/nxp/imx-mipi-csis.c
index fc89325f2f94..985be511bcd0 100644
--- a/drivers/media/platform/nxp/imx-mipi-csis.c
+++ b/drivers/media/platform/nxp/imx-mipi-csis.c
@@ -967,6 +967,9 @@ static int mipi_csis_s_stream(struct v4l2_subdev *sd, int enable)
 	format = v4l2_subdev_state_get_format(state, CSIS_PAD_SINK);
 	csis_fmt = find_csis_format(format->code);
 
+	csis->bus.num_data_lanes = v4l2_get_active_data_lanes(csis->source.pad,
+							      csis->max_data_lanes);
+
 	ret = mipi_csis_calculate_params(csis, csis_fmt);
 	if (ret < 0)
 		goto err_unlock;
-- 
2.43.0

Re: [PATCH v2 1/3] media: v4l: Add helper to get number of active lanes via a pad

[Frank Li]

On Wed, Sep 03, 2025 at 11:22:40AM +0100, Isaac Scott wrote:
> Sometimes, users will not use all of the MIPI CSI 2 lanes available when
> connecting to the MIPI CSI receiver of their device. Add a helper
> function that checks the mbus_config for the device driver to allow
> users to define the number of active data lanes through the
> get_mbus_config op.
>
> If the driver does not implement this op, fall back to using the number
> of data lanes specified in device tree.
>
> Signed-off-by: Isaac Scott <isaac.scott@ideasonboard.com>

Reviewed-by: Frank Li <Frank.Li@nxp.com>
> ---
>  drivers/media/v4l2-core/v4l2-common.c | 25 +++++++++++++++++++++++++
>  include/media/v4l2-common.h           |  1 +
>  2 files changed, 26 insertions(+)
>
> diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c
> index 6e585bc76367..8683107b3704 100644
> --- a/drivers/media/v4l2-core/v4l2-common.c
> +++ b/drivers/media/v4l2-core/v4l2-common.c
> @@ -571,6 +571,31 @@ s64 __v4l2_get_link_freq_pad(struct media_pad *pad, unsigned int mul,
>  	return __v4l2_get_link_freq_ctrl(sd->ctrl_handler, mul, div);
>  }
>  EXPORT_SYMBOL_GPL(__v4l2_get_link_freq_pad);
> +
> +unsigned int v4l2_get_active_data_lanes(const struct media_pad *pad, unsigned int dt_lanes)
> +{
> +	struct v4l2_mbus_config mbus_config = {};
> +	struct v4l2_subdev *sd;
> +	unsigned int lanes;
> +	int ret;
> +
> +	sd = media_entity_to_v4l2_subdev(pad->entity);
> +	ret = v4l2_subdev_call(sd, pad, get_mbus_config, pad->index,
> +			       &mbus_config);
> +	if (ret < 0 && ret != -ENOIOCTLCMD)
> +		return ret;
> +
> +	if (!mbus_config.bus.mipi_csi2.num_data_lanes)
> +		return dt_lanes;
> +
> +	lanes = mbus_config.bus.mipi_csi2.num_data_lanes;
> +
> +	if (lanes < 0 || lanes > dt_lanes)
> +		return -EINVAL;
> +
> +	return lanes;
> +}
> +EXPORT_SYMBOL_GPL(v4l2_get_active_data_lanes);
>  #endif /* CONFIG_MEDIA_CONTROLLER */
>
>  /*
> diff --git a/include/media/v4l2-common.h b/include/media/v4l2-common.h
> index 0a43f56578bc..3f8937260c76 100644
> --- a/include/media/v4l2-common.h
> +++ b/include/media/v4l2-common.h
> @@ -584,6 +584,7 @@ int v4l2_fill_pixfmt_mp(struct v4l2_pix_format_mplane *pixfmt, u32 pixelformat,
>  	(pad, mul, div)
>  s64 __v4l2_get_link_freq_pad(struct media_pad *pad, unsigned int mul,
>  			     unsigned int div);
> +unsigned int v4l2_get_active_data_lanes(const struct media_pad *pad, unsigned int dt_lanes);
>  #else
>  #define v4l2_get_link_freq(handler, mul, div)		\
>  	__v4l2_get_link_freq_ctrl(handler, mul, div)
> --
> 2.43.0
>

Re: [PATCH v2 2/3] media: imx-mipi-csis: Store the number of data_lanes configured in dt

[Frank Li]

On Wed, Sep 03, 2025 at 11:22:41AM +0100, Isaac Scott wrote:
> The number of lanes actively used by a MIPI CSI transmitter may differ
> from that which is defined in device tree. To allow us to be able to set
> the number of configured lanes without changing the maximum lane count,
> store the number of lanes configured in device tree, and adjust the
> debug print to reflect the device tree value.
>
> Signed-off-by: Isaac Scott <isaac.scott@ideasonboard.com>
> ---
>  drivers/media/platform/nxp/imx-mipi-csis.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/platform/nxp/imx-mipi-csis.c b/drivers/media/platform/nxp/imx-mipi-csis.c
> index 2beb5f43c2c0..fc89325f2f94 100644
> --- a/drivers/media/platform/nxp/imx-mipi-csis.c
> +++ b/drivers/media/platform/nxp/imx-mipi-csis.c
> @@ -313,6 +313,8 @@ struct mipi_csis_device {
>  	u32 hs_settle;
>  	u32 clk_settle;
>
> +	unsigned int max_data_lanes;
> +

is num_data_lanes better? you get from vep.bus.mipi_csi2.num_data_lanes

Frank

>  	spinlock_t slock;	/* Protect events */
>  	struct mipi_csis_event events[MIPI_CSIS_NUM_EVENTS];
>  	struct dentry *debugfs_root;
> @@ -1299,8 +1301,9 @@ static int mipi_csis_async_register(struct mipi_csis_device *csis)
>  	}
>
>  	csis->bus = vep.bus.mipi_csi2;
> +	csis->max_data_lanes = vep.bus.mipi_csi2.num_data_lanes;
>
> -	dev_dbg(csis->dev, "data lanes: %d\n", csis->bus.num_data_lanes);
> +	dev_dbg(csis->dev, "data lanes: %d\n", csis->max_data_lanes);
>  	dev_dbg(csis->dev, "flags: 0x%08x\n", csis->bus.flags);
>
>  	asd = v4l2_async_nf_add_fwnode_remote(&csis->notifier, ep,
> --
> 2.43.0
>

Re: [PATCH v2 3/3] media: imx-mipi-csis: Get number of active lanes via mbus_config

[Frank Li]

On Wed, Sep 03, 2025 at 11:22:42AM +0100, Isaac Scott wrote:
> The number of lanes actively used by a MIPI CSI transmitter may differ
> from that which is defined in device tree. As such, call on
> v4l2_get_active_data_lanes to check if the driver reports a

function need (), v4l2_get_active_data_lanes()

> differing number of lanes to device tree, and use that number of active
> lanes.
>
> If the number of active data lanes is invalid, or the op is not
> supported, it will use the number of lanes defined in device tree.

remove "it will" to keep simple.

Frank
>
> Signed-off-by: Isaac Scott <isaac.scott@ideasonboard.com>
> ---
>  drivers/media/platform/nxp/imx-mipi-csis.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/media/platform/nxp/imx-mipi-csis.c b/drivers/media/platform/nxp/imx-mipi-csis.c
> index fc89325f2f94..985be511bcd0 100644
> --- a/drivers/media/platform/nxp/imx-mipi-csis.c
> +++ b/drivers/media/platform/nxp/imx-mipi-csis.c
> @@ -967,6 +967,9 @@ static int mipi_csis_s_stream(struct v4l2_subdev *sd, int enable)
>  	format = v4l2_subdev_state_get_format(state, CSIS_PAD_SINK);
>  	csis_fmt = find_csis_format(format->code);
>
> +	csis->bus.num_data_lanes = v4l2_get_active_data_lanes(csis->source.pad,
> +							      csis->max_data_lanes);
> +
>  	ret = mipi_csis_calculate_params(csis, csis_fmt);
>  	if (ret < 0)
>  		goto err_unlock;
> --
> 2.43.0
>