[PATCH] media: rkisp1: Reduce min_queued_buffers to 1

[Sebastian Fricke]

On 07.10.2024 16:47, Laurent Pinchart wrote:
>On Mon, Oct 07, 2024 at 02:57:30PM +0200, Sebastian Fricke wrote:
>> 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?
>
>Isn't that exactly what this patch is doing ?

Oh *facepalm* ... I missed that please disregard ...

but my question below remains whether to not just change the value.

Sorry,
Sebastian

>
>> 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.
>>
>> > +	q->min_queued_buffers = 1;
>> >  	q->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
>> >  	q->lock = &node->vlock;
>> >  	q->dev = cap->rkisp1->dev;
>
>-- 
>Regards,
>
>Laurent Pinchart
Sebastian Fricke
Consultant Software Engineer

Collabora Ltd
Platinum Building, St John's Innovation Park, Cambridge CB4 0DS, UK
Registered in England & Wales no 5513718.