media: staging: rkisp1: cap: protect access to buf with the spin lock

The function 'rkisp1_stream_start' calls 'rkisp1_set_next_buf'
which access the buffers, so the call should be protected by
taking the cap->buf.lock.
After this patch, all locks are reviewed and commented so remove
the TODO item "review and comment every lock"
Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@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/TODO

 * Fix pad format size for statistics and parameters entities.
 * Fix checkpatch errors.
-* Review and comment every lock
 * Add uapi docs. Remember to add documentation of how quantization is handled.
 * streaming paths (mainpath and selfpath) check if the other path is streaming
 in several places of the code, review this, specially that it doesn't seem it

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

@@ -955,6 +955,7 @@ static void rkisp1_stream_start(struct rkisp1_capture *cap)
 	cap->ops->config(cap);
 
 	/* Setup a buffer for the next frame */
+	spin_lock_irq(&cap->buf.lock);
 	rkisp1_set_next_buf(cap);
 	cap->ops->enable(cap);
 	/* It's safe to config ACTIVE and SHADOW regs for the
@@ -972,6 +973,7 @@ static void rkisp1_stream_start(struct rkisp1_capture *cap)
 			     RKISP1_CIF_MI_INIT_SOFT_UPD, RKISP1_CIF_MI_INIT);
 		rkisp1_set_next_buf(cap);
 	}
+	spin_unlock_irq(&cap->buf.lock);
 	cap->is_streaming = true;
 }