Re: [PATCH v3] media: rkisp1: Remove min_queued_buffers

From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Cc: Dafna Hirschfeld <dafna@fastmail.com>,
	Hans Verkuil <hverkuil@xs4all.nl>,
	"open list:ROCKCHIP ISP V1 DRIVER" <linux-media@vger.kernel.org>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Heiko Stuebner <heiko@sntech.de>,
	"open list:ROCKCHIP ISP V1 DRIVER"
	<linux-rockchip@lists.infradead.org>,
	Adam Pigg <adam@piggz.co.uk>
Subject: Re: [PATCH v3] media: rkisp1: Remove min_queued_buffers
Date: Tue, 29 Oct 2024 13:29:38 +0200	[thread overview]
Message-ID: <20241029112938.GK22600@pendragon.ideasonboard.com> (raw)
In-Reply-To: <20241029082117.55385-1-jacopo.mondi@ideasonboard.com>

Hi Jacopo,

Thank you for the patch.

On Tue, Oct 29, 2024 at 09:21:16AM +0100, Jacopo Mondi wrote:
> There apparently is no reason to require 3 queued buffers for RkISP1,
> as the driver operates with a scratch buffer where data can be
> directed to if there's no available buffer provided by userspace.
> 
> Reduce the number of required buffers to 0 by removing the
> initialization of min_queued_buffers, to allow applications to operate
> by queueing capture buffers on-demand.
> 
> Tested with libcamera, by operating with a single capture request. The
> same request (and the 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@ideasonboard.com>

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> ---
> v2->v3:
> - Remove min_queued_buffers initialization
> 
> v1->v2:
> The first version of this patch set min_queued_buffers to 1, but setting it
> to 0 doesn't compromise operations and it's even better as it allows application
> to queue buffers to the capture devices on-demand. If a buffer is not provided
> to the DMA engines, image data gets directed to the driver's internal scratch
> buffer.
> ---
>  drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c b/drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c
> index 2bddb4fa8a5c..2f0c610e74b9 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 +1561,6 @@ 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;
>  	q->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
>  	q->lock = &node->vlock;
>  	q->dev = cap->rkisp1->dev;

-- 
Regards,

Laurent Pinchart

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