[PATCH 2/5] media: nxp: imx8-isi: Fix per-stream reference counting for multiplexed streams
Frank Li
Frank.li at oss.nxp.com
Mon Jun 29 07:55:16 PDT 2026
On Mon, Jun 29, 2026 at 03:44:56PM +0800, Guoniu Zhou wrote:
subject: use per-stream state to fix ...
> The ISI crossbar fails to properly enable multiple streams from different
> virtual channels on the same input pad. Only the first stream gets enabled
> in hardware, subsequent streams are silently ignored.
>
> The driver uses a single enable_count per input to track the input state.
> When enable_count is non-zero, the code assumes the input is already active
> and skips calling v4l2_subdev_enable_streams() for additional streams:
>
> Call 1: enable_streams(stream 0)
> -> enable_count == 0, enable gasket and stream 0 in hardware
> -> enable_count = 1
>
> Call 2: enable_streams(stream 1)
> -> enable_count == 1, skip hardware enable (BUG!)
> -> enable_count = 2
> -> stream 1 never gets enabled
>
> Similarly on disable, when enable_count reaches zero, ALL streams are
> disabled regardless of which streams are actually still active.
>
> Fix this by tracking per-stream state using:
> - enabled_streams (u64 bitmask): tracks which streams are currently enabled
> - enabled_count[] (array): per-stream reference counter to support the same
> stream being enabled/disabled multiple times
>
> Now each stream is independently enabled/disabled in hardware based on the
> enabled_streams bitmask, while enabled_count[] provides reference counting
> for scenarios where the same stream is enabled multiple times, such as
> duplicate cases in the ISI stream.
>
> Fixes: cf21f328fcaf ("media: nxp: Add i.MX8 ISI driver")
> Cc: stable at vger.kernel.org
> Signed-off-by: Guoniu Zhou <guoniu.zhou at oss.nxp.com>
> ---
> .../media/platform/nxp/imx8-isi/imx8-isi-core.h | 4 +-
> .../platform/nxp/imx8-isi/imx8-isi-crossbar.c | 121 +++++++++++++++++----
> 2 files changed, 104 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.h b/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.h
> index 7547a6559d4c..bb2cfba27e20 100644
> --- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.h
> +++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.h
> @@ -185,7 +185,9 @@ struct mxc_isi_dma_buffer {
> };
>
> struct mxc_isi_input {
> - unsigned int enable_count;
> + u64 enabled_streams;
> + /* Counter per stream */
> + unsigned int *enabled_count;
> };
>
> struct mxc_isi_crossbar {
> diff --git a/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c b/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c
> index 29f14d30dbbb..a4a063c60c76 100644
> --- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c
> +++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c
> @@ -345,6 +345,8 @@ static int mxc_isi_crossbar_enable_streams(struct v4l2_subdev *sd,
> struct mxc_isi_crossbar *xbar = to_isi_crossbar(sd);
> struct v4l2_subdev *remote_sd;
> struct mxc_isi_input *input;
> + u64 streams_to_enable;
> + unsigned long stream;
> u64 sink_streams;
> u32 sink_pad;
> u32 remote_pad;
> @@ -358,30 +360,47 @@ static int mxc_isi_crossbar_enable_streams(struct v4l2_subdev *sd,
>
> input = &xbar->inputs[sink_pad];
>
> - /*
> - * TODO: Track per-stream enable counts to support multiplexed
> - * streams.
> - */
> - if (!input->enable_count) {
> + if (!input->enabled_streams) {
> ret = mxc_isi_crossbar_gasket_enable(xbar, state, remote_sd,
> remote_pad, sink_pad);
> if (ret)
> return ret;
> + }
> +
> + /*
> + * Track per-stream enable counts to support multiplexed streams.
> + * Only enable streams that are not already enabled.
> + */
> + streams_to_enable = sink_streams & ~input->enabled_streams;
>
> + if (streams_to_enable) {
> ret = v4l2_subdev_enable_streams(remote_sd, remote_pad,
> - sink_streams);
> + streams_to_enable);
> if (ret) {
> dev_err(xbar->isi->dev,
> "failed to enable streams 0x%llx on '%s':%u: %d\n",
> - sink_streams, remote_sd->name, remote_pad, ret);
> - mxc_isi_crossbar_gasket_disable(xbar, sink_pad);
> - return ret;
> + streams_to_enable, remote_sd->name, remote_pad, ret);
> + goto err_gasket_disable;
> }
> +
> + input->enabled_streams |= streams_to_enable;
> }
>
> - input->enable_count++;
> + /* Increment reference count for all requested streams */
> + for (stream = 0; stream < xbar->num_sources; stream++) {
> + if (!(sink_streams & BIT(stream)))
> + continue;
> +
> + input->enabled_count[stream]++;
> + }
>
> return 0;
> +
> +err_gasket_disable:
> + if (!input->enabled_streams)
> + mxc_isi_crossbar_gasket_disable(xbar, sink_pad);
> +
> + return ret;
> }
>
> static int mxc_isi_crossbar_disable_streams(struct v4l2_subdev *sd,
> @@ -391,6 +410,8 @@ static int mxc_isi_crossbar_disable_streams(struct v4l2_subdev *sd,
> struct mxc_isi_crossbar *xbar = to_isi_crossbar(sd);
> struct v4l2_subdev *remote_sd;
> struct mxc_isi_input *input;
> + u64 streams_to_disable = 0;
> + unsigned long stream;
> u64 sink_streams;
> u32 sink_pad;
> u32 remote_pad;
> @@ -404,19 +425,36 @@ static int mxc_isi_crossbar_disable_streams(struct v4l2_subdev *sd,
>
> input = &xbar->inputs[sink_pad];
>
> - input->enable_count--;
> + /*
> + * Decrease the enable count for each stream. Only disable streams
> + * whose count reaches zero.
> + */
> + for (stream = 0; stream < xbar->num_sources; stream++) {
> + if (!(sink_streams & BIT(stream)))
> + continue;
>
> - if (!input->enable_count) {
> - ret = v4l2_subdev_disable_streams(remote_sd, remote_pad,
> - sink_streams);
> - if (ret)
> - dev_err(xbar->isi->dev,
> - "failed to disable streams 0x%llx on '%s':%u: %d\n",
> - sink_streams, remote_sd->name, remote_pad, ret);
> + if (!(input->enabled_streams & BIT(stream)))
> + continue;
>
> - mxc_isi_crossbar_gasket_disable(xbar, sink_pad);
> + if (--input->enabled_count[stream] == 0)
> + streams_to_disable |= BIT(stream);
> }
>
> + if (!streams_to_disable)
> + return 0;
> +
> + ret = v4l2_subdev_disable_streams(remote_sd, remote_pad,
> + streams_to_disable);
> + if (ret)
> + dev_err(xbar->isi->dev,
> + "failed to disable streams 0x%llx on '%s':%u: %d\n",
> + streams_to_disable, remote_sd->name, remote_pad, ret);
> +
> + input->enabled_streams &= ~streams_to_disable;
> +
> + if (!input->enabled_streams)
> + mxc_isi_crossbar_gasket_disable(xbar, sink_pad);
> +
> return ret;
> }
>
> @@ -447,6 +485,42 @@ static const struct media_entity_operations mxc_isi_cross_entity_ops = {
> * Init & cleanup
> */
>
> +static int mxc_isi_stream_counters_alloc(struct mxc_isi_crossbar *xbar)
> +{
> + unsigned int i;
> + int ret;
> +
> + for (i = 0; i < xbar->num_sinks; ++i) {
> + struct mxc_isi_input *input = &xbar->inputs[i];
> +
> + input->enabled_count = kcalloc(xbar->num_sources,
> + sizeof(*input->enabled_count),
> + GFP_KERNEL);
kzalloc_objs();
Frank
> + if (!input->enabled_count) {
> + dev_err(xbar->isi->dev,
> + "failed to alloc memory for ISI input(%d)\n", i);
> + ret = -ENOMEM;
> + goto err_free;
> + }
> + }
> +
> + return 0;
> +
> +err_free:
> + while (i--)
> + kfree(xbar->inputs[i].enabled_count);
> +
> + return ret;
> +}
> +
> +static void mxc_isi_stream_counters_free(struct mxc_isi_crossbar *xbar)
> +{
> + unsigned int i;
> +
> + for (i = 0; i < xbar->num_sinks; ++i)
> + kfree(xbar->inputs[i].enabled_count);
> +}
> +
> int mxc_isi_crossbar_init(struct mxc_isi_dev *isi)
> {
> struct mxc_isi_crossbar *xbar = &isi->crossbar;
> @@ -484,6 +558,10 @@ int mxc_isi_crossbar_init(struct mxc_isi_dev *isi)
> goto err_free;
> }
>
> + ret = mxc_isi_stream_counters_alloc(xbar);
> + if (ret)
> + goto err_free;
> +
> for (i = 0; i < xbar->num_sinks; ++i)
> xbar->pads[i].flags = MEDIA_PAD_FL_SINK
> | MEDIA_PAD_FL_MUST_CONNECT;
> @@ -492,7 +570,7 @@ int mxc_isi_crossbar_init(struct mxc_isi_dev *isi)
>
> ret = media_entity_pads_init(&sd->entity, num_pads, xbar->pads);
> if (ret)
> - goto err_free;
> + goto err_free_cnt;
>
> ret = v4l2_subdev_init_finalize(sd);
> if (ret < 0)
> @@ -502,6 +580,8 @@ int mxc_isi_crossbar_init(struct mxc_isi_dev *isi)
>
> err_entity:
> media_entity_cleanup(&sd->entity);
> +err_free_cnt:
> + mxc_isi_stream_counters_free(xbar);
> err_free:
> kfree(xbar->pads);
> kfree(xbar->inputs);
> @@ -512,6 +592,7 @@ int mxc_isi_crossbar_init(struct mxc_isi_dev *isi)
> void mxc_isi_crossbar_cleanup(struct mxc_isi_crossbar *xbar)
> {
> v4l2_subdev_cleanup(&xbar->sd);
> + mxc_isi_stream_counters_free(xbar);
> media_entity_cleanup(&xbar->sd.entity);
> kfree(xbar->pads);
> kfree(xbar->inputs);
>
> --
> 2.34.1
>
>
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