Hi, Julien:

On Thu, 2024-07-04 at 15:36 +0200, Julien Stephan wrote:

 	 
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 From: Phi-bang Nguyen [off-list ref]

This driver provides a path to bypass the SoC ISP so that image data
coming from the SENINF can go directly into memory without any image
processing. This allows the use of an external ISP.

Signed-off-by: Phi-bang Nguyen <redacted>
Signed-off-by: Florian Sylvestre <redacted>
[Paul Elder fix irq locking]
Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Co-developed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Co-developed-by: Julien Stephan <jstephan@baylibre.com>
Signed-off-by: Julien Stephan <jstephan@baylibre.com>
---

[snip]

+static int mtk_cam_vb2_start_streaming(struct vb2_queue *vq,
+       unsigned int count)
+{
+struct mtk_cam_dev *cam = vb2_get_drv_priv(vq);
+struct mtk_cam_dev_buffer *buf;
+struct mtk_cam_video_device *vdev =
+vb2_queue_to_mtk_cam_video_device(vq);
+struct device *dev = cam->dev;
+const struct v4l2_pix_format_mplane *fmt = &vdev->format;
+int ret;
+unsigned long flags;
+
+if (pm_runtime_get_sync(dev) < 0) {
+dev_err(dev, "failed to get pm_runtime\n");
+pm_runtime_put_autosuspend(dev);
+return -1;
+}
+
+(*cam->hw_functions->mtk_cam_setup)(cam, fmt->width, fmt->height,
+fmt->plane_fmt[0].bytesperline, vdev->fmtinfo->code);
+
+
+/* Enable CMOS and VF */
+mtk_cam_cmos_vf_enable(cam, true, true);
+
+mutex_lock(&cam->op_lock);
+
+ret = mtk_cam_verify_format(cam);
+if (ret < 0)
+goto fail_unlock;
+
+/* Start streaming of the whole pipeline now*/
+if (!cam->pipeline.start_count) {
+ret = media_pipeline_start(vdev->vdev.entity.pads,
+   &cam->pipeline);
+if (ret) {
+dev_err(dev, "failed to start pipeline:%d\n", ret);
+goto fail_unlock;
+}
+}
+
+/* Media links are fixed after media_pipeline_start */
+cam->stream_count++;
+
+cam->sequence = (unsigned int)-1;
+
+/* Stream on the sub-device */
+ret = v4l2_subdev_call(&cam->subdev, video, s_stream, 1);
+if (ret)
+goto fail_no_stream;
+
+mutex_unlock(&cam->op_lock);
+
+/* Create dummy buffer */
+cam->dummy_size = fmt->plane_fmt[0].sizeimage;
+
+cam->dummy.vaddr = dma_alloc_coherent(cam->dev, cam->dummy_size,
+      &cam->dummy.daddr, GFP_KERNEL);

Dummy buffer cost much in DRAM footprint. I think we can get rid of
this dummy buffer. If no buffer is queued from user space, call
mtk_camsv30_cmos_vf_hw_disable() to stop write data into DRAM. After
buffer is queued from user space, call mtk_camsv30_cmos_vf_hw_enable()
to start write data into DRAM.

Regards,
CK

+if (!cam->dummy.vaddr) {
+ret = -ENOMEM;
+goto fail_no_buffer;
+}
+
+/* update first buffer address */
+
+/* added the buffer into the tracking list */
+spin_lock_irqsave(&cam->irqlock, flags);
+if (list_empty(&cam->buf_list)) {
+(*cam->hw_functions->mtk_cam_update_buffers_add)(cam, &cam->dummy);
+cam->is_dummy_used = true;
+} else {
+buf = list_first_entry_or_null(&cam->buf_list,
+       struct mtk_cam_dev_buffer,
+       list);
+(*cam->hw_functions->mtk_cam_update_buffers_add)(cam, buf);
+cam->is_dummy_used = false;
+}
+spin_unlock_irqrestore(&cam->irqlock, flags);
+
+return 0;
+
+fail_no_buffer:
+mutex_lock(&cam->op_lock);
+v4l2_subdev_call(&cam->subdev, video, s_stream, 0);
+fail_no_stream:
+cam->stream_count--;
+if (cam->stream_count == 0)
+media_pipeline_stop(vdev->vdev.entity.pads);
+fail_unlock:
+mutex_unlock(&cam->op_lock);
+mtk_cam_vb2_return_all_buffers(cam, VB2_BUF_STATE_QUEUED);
+
+return ret;
+}
+