From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from madras.collabora.co.uk (madras.collabora.co.uk [46.235.227.172]) (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 C68B54EB42 for ; Tue, 28 Nov 2023 10:26:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b="fPSIAFQe" Received: from [100.122.216.38] (ec2-34-240-57-77.eu-west-1.compute.amazonaws.com [34.240.57.77]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: benjamin.gaignard) by madras.collabora.co.uk (Postfix) with ESMTPSA id 1D0EF6607295; Tue, 28 Nov 2023 10:26:43 +0000 (GMT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1701167204; bh=wnu068ECaNnR7zM2tCS6WGVU5g0Vyny4l5k0cqi5/Gk=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=fPSIAFQe+6bLt14IZnT7Oq4e2qP9zCUUu1mEtQ5CevwcHsIFRBtsaLBWGMyrc8y90 evscUsbWNpKSG9kHvDOqeRl9iZUjmwzUgr9iKXjMG2EX0YcjrxnDZouGMEehWJe0Aa 61o7FxguyZkUx7b51F3pHeLokSiqjzszdNZrin3Abt2joXa4YXnuMFA5GJT0NKkNqH IZ8T6bEuS6RlUSmFer/Jqkr6Pnv4f66UiMYWNj5Q9r+T3pn4abktqtXVXAgtmb798l 5VbFKYCLbmeyOioDfpKiiYgsKC8QrpP75gwPYKYjqts7Eu39fSJQAtwESJQtClZpxT riuckDGEZN1qg== Message-ID: <995eb6c2-cc7f-4217-bc37-4ab1a32f36ee@collabora.com> Date: Tue, 28 Nov 2023 11:26:40 +0100 Precedence: bulk X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 07/55] media: imx8-isi: Stop abusing of min_buffers_needed field Content-Language: en-US To: Tomasz Figa Cc: Laurent Pinchart , 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 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> From: Benjamin Gaignard In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Le 28/11/2023 à 10:35, Tomasz Figa a écrit : > 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. Unfortunately isn't not true either, for example verisilicon driver use these function but doesn't need DMA engine. I haven't found yet a 100% criteria to decide if driver use or not DMA engine so I plan to fix case by case given maintainers remarks. Regards, Benjamin > > Best regards, > Tomasz > >> 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. >> >> Regards, >> Benjamin >> >>>> 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; >>>>