media: staging: rkisp1: cap: don't set next buffer from rkisp1_vb2_bu…

…f_queue

The function 'rkisp1_vb2_buf_queue' sets the next buffer directly
in case the capture is already streaming but no frame yet arrived
from the sensor. This is an optimization that tries to avoid
dropping a frame.
The call atomic_read(&cap->rkisp1->isp.frame_sequence) is used
to check if a frame arrived. Reading the 'frame_sequence' should
be avoided outside irq handlers to avoid race conditions.

This patch removes this optimization. Dropping of the first
frames can be avoided if userspace queues the buffers before
start streaming. If userspace starts queueing buffers
only after calling 'streamon' he risks frame drops anyway.

Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Acked-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/staging/media/rkisp1/rkisp1-capture.c

@@ -743,18 +743,7 @@ static void rkisp1_vb2_buf_queue(struct vb2_buffer *vb)
 		     ispbuf->buff_addr[RKISP1_PLANE_CB]);
 
 	spin_lock_irqsave(&cap->buf.lock, flags);
-
-	/*
-	 * If there's no next buffer assigned, queue this buffer directly
-	 * as the next buffer, and update the memory interface.
-	 */
-	if (cap->is_streaming && !cap->buf.next &&
-	    atomic_read(&cap->rkisp1->isp.frame_sequence) == -1) {
-		cap->buf.next = ispbuf;
-		rkisp1_set_next_buf(cap);
-	} else {
-		list_add_tail(&ispbuf->queue, &cap->buf.queue);
-	}
+	list_add_tail(&ispbuf->queue, &cap->buf.queue);
 	spin_unlock_irqrestore(&cap->buf.lock, flags);
 }