[RFC PATCH v2 4/4] media: iris: Let a resolution change drain before stopping CAPTURE

[Christian Cortner <ccortner@gmail.com>]

ffmpeg's h264_v4l2m2m stops CAPTURE about 10 us after it dequeues a
source change event. If the stop reaches the firmware before the
PSC_LAST buffer, that buffer still arrives (1.3 ms later in a trace),
iris_inst_sub_state_change_drc_last() rejects it, and the instance
goes to IRIS_INST_ERROR: no more buffers come back.

Wait up to 500 ms in iris_vb2_stop_streaming() for a pending source
change to drain, and warn when it does not.

Fixes: 84e17adae3e3 ("media: iris: add support for dynamic resolution change")
Assisted-by: LLM sparse smatch
---
 .../media/platform/qcom/iris/iris_instance.h  |  3 +++
 drivers/media/platform/qcom/iris/iris_state.c |  8 +++++++-
 drivers/media/platform/qcom/iris/iris_vb2.c   | 20 +++++++++++++++++++
 drivers/media/platform/qcom/iris/iris_vidc.c  |  1 +
 4 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/qcom/iris/iris_instance.h b/drivers/media/platform/qcom/iris/iris_instance.h
index 771269e705d9..1013ed2911a1 100644
--- a/drivers/media/platform/qcom/iris/iris_instance.h
+++ b/drivers/media/platform/qcom/iris/iris_instance.h
@@ -7,6 +7,7 @@
 #define __IRIS_INSTANCE_H__
 
 #include <linux/kref.h>
+#include <linux/wait.h>
 
 #include <media/v4l2-ctrls.h>
 
@@ -56,6 +57,7 @@ struct iris_hfi_session_ops;
  * @metadata_idx: index for metadata buffer
  * @codec: codec type
  * @last_buffer_dequeued: a flag to indicate that last buffer is sent by driver
+ * @drc_wq: woken when IRIS_INST_SUB_DRC_LAST is set
  * @last_buf_ns: start time of received input buffer for current one second FPS window
  * @frame_counter: input buffer counter for current one second FPS window
  * @frame_rate: frame rate of current instance
@@ -104,6 +106,7 @@ struct iris_inst {
 	u32				metadata_idx;
 	u32				codec;
 	bool				last_buffer_dequeued;
+	wait_queue_head_t		drc_wq;
 	u64				last_buf_ns;
 	u32				frame_counter;
 	u32				frame_rate;
diff --git a/drivers/media/platform/qcom/iris/iris_state.c b/drivers/media/platform/qcom/iris/iris_state.c
index 5552725c614e..dd8e0093b972 100644
--- a/drivers/media/platform/qcom/iris/iris_state.c
+++ b/drivers/media/platform/qcom/iris/iris_state.c
@@ -209,6 +209,7 @@ int iris_inst_sub_state_change_drain_last(struct iris_inst *inst)
 int iris_inst_sub_state_change_drc_last(struct iris_inst *inst)
 {
 	enum iris_inst_sub_state set_sub_state;
+	int ret;
 
 	if (inst->sub_state & IRIS_INST_SUB_DRC_LAST)
 		return -EINVAL;
@@ -222,7 +223,12 @@ int iris_inst_sub_state_change_drc_last(struct iris_inst *inst)
 
 	set_sub_state = IRIS_INST_SUB_DRC_LAST | IRIS_INST_SUB_OUTPUT_PAUSE;
 
-	return iris_inst_change_sub_state(inst, 0, set_sub_state);
+	ret = iris_inst_change_sub_state(inst, 0, set_sub_state);
+	/* a CAPTURE STREAMOFF may be waiting, see iris_vb2_stop_streaming() */
+	if (!ret)
+		wake_up_all(&inst->drc_wq);
+
+	return ret;
 }
 
 int iris_inst_sub_state_change_pause(struct iris_inst *inst, u32 plane)
diff --git a/drivers/media/platform/qcom/iris/iris_vb2.c b/drivers/media/platform/qcom/iris/iris_vb2.c
index bb713da20605..2460778c408d 100644
--- a/drivers/media/platform/qcom/iris/iris_vb2.c
+++ b/drivers/media/platform/qcom/iris/iris_vb2.c
@@ -228,6 +228,15 @@ int iris_vb2_start_streaming(struct vb2_queue *q, unsigned int count)
 	return ret;
 }
 
+/* a source change whose drain the firmware has not completed yet */
+static bool iris_drc_draining(struct iris_inst *inst)
+{
+	enum iris_inst_sub_state sub_state = READ_ONCE(inst->sub_state);
+
+	return sub_state & IRIS_INST_SUB_DRC &&
+	       !(sub_state & IRIS_INST_SUB_DRC_LAST);
+}
+
 void iris_vb2_stop_streaming(struct vb2_queue *q)
 {
 	struct iris_inst *inst;
@@ -238,6 +247,17 @@ void iris_vb2_stop_streaming(struct vb2_queue *q)
 	if (V4L2_TYPE_IS_CAPTURE(q->type) && inst->state == IRIS_INST_INIT)
 		return;
 
+	/*
+	 * Stopping CAPTURE before the firmware has drained a pending
+	 * resolution change leaves the change incomplete, and decoding stalls
+	 * after the next STREAMON. Wait up to 500 ms for the drain.
+	 */
+	if (V4L2_TYPE_IS_CAPTURE(q->type) &&
+	    !wait_event_timeout(inst->drc_wq, !iris_drc_draining(inst),
+				msecs_to_jiffies(500)))
+		dev_warn(inst->core->dev,
+			 "resolution change drain timed out, stopping CAPTURE\n");
+
 	mutex_lock(&inst->lock);
 
 	if (!V4L2_TYPE_IS_OUTPUT(q->type) &&
diff --git a/drivers/media/platform/qcom/iris/iris_vidc.c b/drivers/media/platform/qcom/iris/iris_vidc.c
index 05aab6e3005d..0df0a5915e16 100644
--- a/drivers/media/platform/qcom/iris/iris_vidc.c
+++ b/drivers/media/platform/qcom/iris/iris_vidc.c
@@ -201,6 +201,7 @@ int iris_open(struct file *filp)
 	INIT_LIST_HEAD(&inst->buffers[BUF_PARTIAL].list);
 	init_completion(&inst->completion);
 	init_completion(&inst->flush_completion);
+	init_waitqueue_head(&inst->drc_wq);
 
 	iris_v4l2_fh_init(inst, filp);
 
-- 
2.56.0