From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6666A4F5F3 for ; Tue, 28 Nov 2023 10:31:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="rrlqwtw2" Received: from pendragon.ideasonboard.com (213-243-189-158.bb.dnainternet.fi [213.243.189.158]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 42A93BB2; Tue, 28 Nov 2023 11:30:36 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1701167436; bh=OXd6WFN+hXV6bAu/T8kro/U446h2pL6QGhhs60nEIi4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=rrlqwtw2gOQQrNMKVW//q6jy+QDsES4uivGL0gr+shfBzULUgf8EIPHup52837x6M lkjEvjo+r5i+ErgPYmnwxd9IEVaCbbtjkecd0f/jixfjw9p22lRsstRNb28SEuU2fe uiM/3GmHY9w/a0YXrbP6QkaEtxAR6gre/elYP32E= Date: Tue, 28 Nov 2023 12:31:17 +0200 From: Laurent Pinchart To: Tomasz Figa Cc: Benjamin Gaignard , hverkuil@xs4all.nl, mchehab@kernel.org, m.szyprowski@samsung.com, matt.ranostay@konsulko.com, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linux-staging@lists.linux.dev, kernel@collabora.com, Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , NXP Linux Team Subject: Re: [PATCH 07/55] media: imx8-isi: Stop abusing of min_buffers_needed field Message-ID: <20231128103117.GF31314@pendragon.ideasonboard.com> References: <20231127165454.166373-1-benjamin.gaignard@collabora.com> <20231127165454.166373-8-benjamin.gaignard@collabora.com> <20231127170700.GC31314@pendragon.ideasonboard.com> <6fa1ec09-3e30-475e-9718-29d23586753e@collabora.com> Precedence: bulk X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Tue, Nov 28, 2023 at 06:35:51PM +0900, Tomasz Figa wrote: > On Tue, Nov 28, 2023 at 6:31 PM Benjamin Gaignard wrote: > > Le 27/11/2023 à 18:07, Laurent Pinchart a écrit : > > > Hi Benjamin, > > > > > > Thank you for the patch. > > > > > > On Mon, Nov 27, 2023 at 05:54:06PM +0100, Benjamin Gaignard wrote: > > >> 'min_buffers_needed' is suppose to be used to indicate the number > > >> of buffers needed by DMA engine to start streaming. > > >> imx8-isi driver doesn't use DMA engine and just want to specify > > > What do you mean, "doesn't use DMA engine" ? The ISI surely has DMA > > > engines :-) > > > > I have done assumption on drivers given if they use or dma_* functions. > > I suspect the use of vb2_dma_sg_plane_desc() and > vb2_dma_contig_plane_dma_addr() may be more correlated to whether > there is a DMA involved or not. Usually V4L2 drivers don't really have > to deal with the DMA API explicitly, because the vb2 framework handles > most of the work. And this is anyway not related to DMA at all, but to the logic each driver implements when it deals with buffers. There's a lower chance a USB driver driver will have a hard requirement for more than one buffer compared to an AMBA/platform/PCI device driver, but at the end of the day, each driver needs to be analyzed individually to check what they require. Benjamin, I think you'll have some more homework to do :-) > > I have considers that all PCI drivers are using DMA engine and > > I don't know the design for each drivers so I hope to get this information > > from maintainers and fix that in v2. > > If imx8-isi driver needs a minimum number of buffers before start streaming > > I will do a v2 and use min_dma_buffers_needed instead. > > > > >> the minimum number of buffers to allocate when calling VIDIOC_REQBUFS. > > >> That 'min_reqbufs_allocation' field purpose so use it. > > >> > > >> Signed-off-by: Benjamin Gaignard > > >> CC: Laurent Pinchart > > >> CC: Mauro Carvalho Chehab > > >> CC: Shawn Guo > > >> CC: Sascha Hauer > > >> CC: Pengutronix Kernel Team > > >> CC: Fabio Estevam > > >> CC: NXP Linux Team > > >> --- > > >> 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 49bca2b01cc6..81673ff9084b 100644 > > >> --- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-video.c > > >> +++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-video.c > > >> @@ -1453,7 +1453,7 @@ int mxc_isi_video_register(struct mxc_isi_pipe *pipe, > > >> 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_buffers_needed = 2; > > >> + q->min_reqbufs_allocation = 2; > > >> q->lock = &video->lock; > > >> q->dev = pipe->isi->dev; > > >> -- Regards, Laurent Pinchart