RE: [PATCH 1/2] media: nxp: imx8-isi: Reduce minimum queued buffers from 2 to 1

Hi Jacopo,

Thanks for your review.

-----Original Message-----
From: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Sent: Wednesday, March 11, 2026 8:51 PM
To: G.N. Zhou (OSS) <redacted>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>; Mauro Carvalho
Chehab [off-list ref]; Frank Li [off-list ref]; Sascha Hauer
[off-list ref]; Pengutronix Kernel Team
[off-list ref]; Fabio Estevam [off-list ref]; linux-
media@vger.kernel.org; imx@lists.linux.dev; linux-arm-
kernel@lists.infradead.org; linux-kernel@vger.kernel.org; Alexi Birlinger
[off-list ref]; G.N. Zhou [off-list ref]
Subject: Re: [PATCH 1/2] media: nxp: imx8-isi: Reduce minimum queued buffers
from 2 to 1

Hello Guoniu

On Wed, Mar 11, 2026 at 04:02:58PM +0800, Guoniu Zhou wrote:

quoted

From: Guoniu Zhou <redacted>

Fix a hang issue when capturing a single frame with applications like
cam in libcamera. It would hang waiting for the driver to complete the
buffer, but streaming never starts because min_queued_buffers was set to 2.

The ISI module uses a ping-pong buffer mechanism that requires two
buffers to be programmed at all times. However, when fewer than 2 user
buffers are available, the driver use internal discard buffers to fill
the remaining slot(s). Reduce minimum queued buffers from 2 to 1
allows streaming to

Does it mean the ISI can use internal buffer discard for both buffer slots ? Can
we make min_queued_buffers == 0 ?

Yes, will update in next version.

quoted

start with a single buffer providing more flexibility for applications.

Signed-off-by: Guoniu Zhou <redacted>
---
 drivers/media/platform/nxp/imx8-isi/imx8-isi-video.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/platform/nxp/imx8-isi/imx8-isi-video.c

b/drivers/media/platform/nxp/imx8-isi/imx8-isi-video.c
index

13682bf6e9f8895bb9eb1f92d5f74b0d5968544e..2405baf21594cd18cf2b3492
3431

quoted

3c5e103b7802 100644

--- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-video.c
+++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-video.c

@@ -1410,7 +1410,7 @@ int mxc_isi_video_register(struct mxc_isi_pipe

*pipe,

quoted

 	q->mem_ops = &vb2_dma_contig_memops;
 	q->buf_struct_size = sizeof(struct mxc_isi_buffer);
 	q->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
-	q->min_queued_buffers = 2;
+	q->min_queued_buffers = 1;
 	q->lock = &video->lock;
 	q->dev = pipe->isi->dev;


--
2.34.1