[PATCH 2/2] media: venus: vdec: Start capture after a seek that streams CAPTURE first

[David Heidelberg via B4 Relay <devnull+david.ixit.cz@kernel.org>]

From: David Heidelberg <david@ixit.cz>

After both queues are streamed off, the decoder sits in
VENUS_DEC_STATE_SEEK. vdec_start_capture() does nothing while OUTPUT is
not streaming, and when OUTPUT is streamed on again, the SEEK path only
queues the DPB buffers if the capture side was already started. So an
application that streams on CAPTURE before OUTPUT gets a decoder that
never receives DPB or capture buffers: the firmware consumes the
bitstream and no frame is ever returned.

The stateful decoder interface does not require either order, and
GStreamer restarts with CAPTURE first. Finish the capture start from the
OUTPUT SEEK path when the CAPTURE queue is already streaming, the same
way vdec_start_capture() does in VENUS_DEC_STATE_DECODING.

Assisted-by: LLM
Signed-off-by: David Heidelberg <david@ixit.cz>
---
 drivers/media/platform/qcom/venus/vdec.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/qcom/venus/vdec.c b/drivers/media/platform/qcom/venus/vdec.c
index 74591c7a820f5..ae6c2fc65404b 100644
--- a/drivers/media/platform/qcom/venus/vdec.c
+++ b/drivers/media/platform/qcom/venus/vdec.c
@@ -1128,33 +1128,51 @@ static int vdec_start_capture(struct venus_inst *inst)
 free_dpb_bufs:
 	venus_helper_free_dpb_bufs(inst);
 err:
 	return ret;
 }
 
 static int vdec_start_output(struct venus_inst *inst)
 {
+	struct vb2_queue *dst_vq;
+	bool cap_waiting;
 	int ret;
 
 	if (inst->codec_state == VENUS_DEC_STATE_SEEK) {
 		ret = venus_helper_process_initial_out_bufs(inst);
 		if (ret)
 			return ret;
 
 		if (inst->next_buf_last) {
 			inst->codec_state = VENUS_DEC_STATE_DRC;
 		} else {
 			inst->codec_state = VENUS_DEC_STATE_DECODING;
 
-			if (inst->streamon_cap) {
+			/*
+			 * If CAPTURE was streamed on first, vdec_start_capture()
+			 * returned early because OUTPUT was not streaming, so
+			 * start the capture side from here.
+			 */
+			dst_vq = v4l2_m2m_get_dst_vq(inst->m2m_ctx);
+			cap_waiting = !inst->streamon_cap && vb2_is_streaming(dst_vq);
+
+			if (inst->streamon_cap || cap_waiting) {
 				ret = venus_helper_queue_dpb_bufs(inst);
 				if (ret)
 					return ret;
 			}
+
+			if (cap_waiting) {
+				ret = venus_helper_process_initial_cap_bufs(inst);
+				if (ret)
+					return ret;
+
+				inst->streamon_cap = 1;
+			}
 		}
 		goto done;
 	}
 
 	if (inst->codec_state == VENUS_DEC_STATE_INIT ||
 	    inst->codec_state == VENUS_DEC_STATE_CAPTURE_SETUP) {
 		ret = venus_helper_process_initial_out_bufs(inst);
 		goto done;

-- 
2.55.0