media: nxp: imx8-isi: Implement per-stream reference counting for multiplexed streams

The ISI crossbar needs to properly enable multiple streams from different
virtual channels on the same input pad. Currently 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
    -> 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.

Implement per-stream state tracking by storing the input index and stream
mask in the mxc_isi_pipe structure. On enable, record which input and
stream the pipe is receiving. On disable, clear the pipe's record and
check if any other pipe is still using the same input stream before
actually disabling it.

Signed-off-by: Guoniu Zhou <guoniu.zhou@oss.nxp.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260728-isi-v5-2-1d22ab91602a@oss.nxp.com
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

drivers/media/platform/nxp/imx8-isi/imx8-isi-core.h

@@ -186,7 +186,7 @@ struct mxc_isi_dma_buffer {
 };
 
 struct mxc_isi_input {
-	unsigned int			enable_count;
+	u64				enabled_streams;
 };
 
 struct mxc_isi_crossbar {
@@ -259,6 +259,14 @@ struct mxc_isi_pipe {
 	u8				acquired_res;
 	u8				chained_res;
 	bool				chained;
+
+	unsigned int			input;
+	/*
+	 * Stream on the connected crossbar input, expressed as a bitmask. Zero
+	 * when the pipeline is disabled, a single bit set when the pipeline is
+	 * enabled (as each pipeline processes a single stream).
+	 */
+	u64				input_stream;
 };
 
 struct mxc_isi_m2m {

drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c

@@ -330,11 +330,32 @@ static int mxc_isi_crossbar_set_routing(struct v4l2_subdev *sd,
 	return __mxc_isi_crossbar_set_routing(sd, state, routing);
 }
 
+/*
+ * Check if a stream on a sink pad is in used by any of the ISI pipelines. The
+ * sink_streams argument is a bitmask that must have a single bit set (enforced
+ * by mxc_isi_crossbar_xlate_streams() translating the single stream mask of the
+ * pipeline to a single stream on the crossbar input side).
+ */
+static bool mxc_isi_crossbar_stream_in_use(const struct mxc_isi_crossbar *xbar,
+					   unsigned int sink_pad, u64 sink_streams)
+{
+	for (unsigned int i = 0; i < xbar->isi->pdata->num_channels; ++i) {
+		const struct mxc_isi_pipe *pipe = &xbar->isi->pipes[i];
+
+		if (pipe->input == sink_pad &&
+		    pipe->input_stream == sink_streams)
+			return true;
+	}
+
+	return false;
+}
+
 static int mxc_isi_crossbar_enable_streams(struct v4l2_subdev *sd,
 					   struct v4l2_subdev_state *state,
 					   u32 pad, u64 streams_mask)
 {
 	struct mxc_isi_crossbar *xbar = to_isi_crossbar(sd);
+	struct mxc_isi_pipe *pipe = &xbar->isi->pipes[pad - xbar->num_sinks];
 	struct v4l2_subdev *remote_sd;
 	struct mxc_isi_input *input;
 	u64 sink_streams;
@@ -351,29 +372,44 @@ 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.
+	 * Check if any other pipe already receives the same input stream.
+	 * If so, just record this pipe's usage and return.
 	 */
-	if (!input->enable_count) {
+	if (mxc_isi_crossbar_stream_in_use(xbar, sink_pad, sink_streams)) {
+		pipe->input = sink_pad;
+		pipe->input_stream = sink_streams;
+		return 0;
+	}
+
+	/* Enable the gasket when the first stream is enabled for this input. */
+	if (!input->enabled_streams) {
 		ret = mxc_isi_crossbar_gasket_enable(xbar, state, remote_sd,
 						     remote_pad, sink_pad);
 		if (ret)
 			return ret;
-
-		ret = v4l2_subdev_enable_streams(remote_sd, remote_pad,
-						 sink_streams);
-		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;
-		}
 	}
 
-	input->enable_count++;
+	ret = v4l2_subdev_enable_streams(remote_sd, remote_pad, sink_streams);
+	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);
+		goto err_gasket_disable;
+	}
+
+	input->enabled_streams |= sink_streams;
+
+	/* Record the input and stream for this pipe. */
+	pipe->input = sink_pad;
+	pipe->input_stream = sink_streams;
 
 	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,
@@ -381,6 +417,7 @@ static int mxc_isi_crossbar_disable_streams(struct v4l2_subdev *sd,
 					    u32 pad, u64 streams_mask)
 {
 	struct mxc_isi_crossbar *xbar = to_isi_crossbar(sd);
+	struct mxc_isi_pipe *pipe = &xbar->isi->pipes[pad - xbar->num_sinks];
 	struct v4l2_subdev *remote_sd;
 	struct mxc_isi_input *input;
 	u64 sink_streams;
@@ -396,18 +433,27 @@ static int mxc_isi_crossbar_disable_streams(struct v4l2_subdev *sd,
 
 	input = &xbar->inputs[sink_pad];
 
-	input->enable_count--;
+	/* Clear the input and stream for this pipe. */
+	pipe->input = UINT_MAX;
+	pipe->input_stream = 0;
 
-	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);
+	/*
+	 * Check if any other pipe receives the same input stream. If so we
+	 * can't disable it yet, so return immediately.
+	 */
+	if (mxc_isi_crossbar_stream_in_use(xbar, sink_pad, sink_streams))
+		return 0;
 
+	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);
+
+	input->enabled_streams &= ~sink_streams;
+
+	if (!input->enabled_streams)
 		mxc_isi_crossbar_gasket_disable(xbar, sink_pad);
-	}
 
 	return ret;
 }

drivers/media/platform/nxp/imx8-isi/imx8-isi-pipe.c

@@ -816,6 +816,7 @@ int mxc_isi_pipe_init(struct mxc_isi_dev *isi, unsigned int id)
 	pipe->acquired_res = 0;
 	pipe->chained_res = 0;
 	pipe->chained = false;
+	pipe->input = UINT_MAX;
 
 	sd = &pipe->sd;
 	v4l2_subdev_init(sd, &mxc_isi_pipe_subdev_ops);