[PATCH] media: rkisp1: Reduce min_queued_buffers to 1

[Sebastian Fricke]

Hey Jacopo,

On 07.10.2024 14:42, Jacopo Mondi wrote:
>There apparently is no reason to require 3 queued buffers to call
>streamon() for the RkISP1 as the driver operates with a scratch buffer
>where frames can be directed to if there's no available buffer provided
>by userspace.
>
>Reduce the number of required buffers to 1 to allow applications to
>operate with a single queued buffer.
>
>Tested with libcamera, by operating with a single capture a request. The
>same request (and associated capture buffer) gets recycled once
>completed. This of course causes a frame rate drop but doesn't hinder
>operations.
>
>Signed-off-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>
>---
>
>Adam,
>   a few months ago you were exercizing your pinhole app with a single capture
>request for StillCapture operations and you got the video device to hang because
>no enough buffers where provided.
>
>This small change should be enough to unblock you. Could you maybe give it a
>spin if you're still working on this ?
>
>Thanks
>   j
>---
>
> drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
>
>diff --git a/drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c b/drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c
>index 2bddb4fa8a5c..34adaecdee54 100644
>--- a/drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c
>+++ b/drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c
>@@ -35,8 +35,6 @@
> #define RKISP1_SP_DEV_NAME	RKISP1_DRIVER_NAME "_selfpath"
> #define RKISP1_MP_DEV_NAME	RKISP1_DRIVER_NAME "_mainpath"
>
>-#define RKISP1_MIN_BUFFERS_NEEDED 3
>-
> enum rkisp1_plane {
> 	RKISP1_PLANE_Y	= 0,
> 	RKISP1_PLANE_CB	= 1,
>@@ -1563,7 +1561,7 @@ static int rkisp1_register_capture(struct rkisp1_capture *cap)
> 	q->ops = &rkisp1_vb2_ops;
> 	q->mem_ops = &vb2_dma_contig_memops;
> 	q->buf_struct_size = sizeof(struct rkisp1_buffer);
>-	q->min_queued_buffers = RKISP1_MIN_BUFFERS_NEEDED;

It looks like RKISP1_MIN_BUFFERS_NEEDED is used only here, so can you
remove the define as well?

rg 'RKISP1_MIN_BUFFERS_NEEDED' 
drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c
38:#define RKISP1_MIN_BUFFERS_NEEDED 3
1566:	q->min_queued_buffers = RKISP1_MIN_BUFFERS_NEEDED;

Or maybe just change the value, but I am not sure whether this can be
considered a magic value.

Regards,
Sebastian Fricke

>+	q->min_queued_buffers = 1;
> 	q->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
> 	q->lock = &node->vlock;
> 	q->dev = cap->rkisp1->dev;
>--
>2.46.1
>
>