From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7CC48CE8E68 for ; Thu, 24 Oct 2024 12:07:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To: Content-Transfer-Encoding:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ortzHB5ZGWllXhL6PwjRGnzN9ka5lOt8LHxudcBkzHI=; b=CUK4xITyLgG9aaO/ObPyYd4myv 4bVJr3h66QOLLvxwPmsEmMJ2bE/ZoMp4/SRTIDg6l77ERbgtzxmY/zcaVt37gU6t695AzfNlHnHQ8 JHPNQ7qq1C9+23evbCem/X2jaxtITrCu6d0HU+I3yi0srg3xHBUnT2D44UdhFOTvSTyEeWV/ufN8d RSY9XDVoa81MSaYZFFBfJWMIFc8aBrmEYdMa/yRLPcNXUc0QmK+4GehsIz1gTRiIYp/nIRZH/PMRA y4CAmHljTf9GEWIw9Sh1ngjKoog+KrnU12ncjXolO4wSJwiVDlYbB2XdUwUFvceJgzHSmn7QCgEzD nbBDtdgg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1t3wc7-00000000I7F-3hfS; Thu, 24 Oct 2024 12:06:51 +0000 Received: from perceval.ideasonboard.com ([213.167.242.64]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1t3waZ-00000000HsR-2aMR; Thu, 24 Oct 2024 12:05:17 +0000 Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id CACC6353; Thu, 24 Oct 2024 14:03:24 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1729771405; bh=Y2wiEUdJrkj/gTQbqaSTmIUpHB5u/DfJRkMeoAaWST4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=eEkZ7aqZNH1bXN4g4FtnDOlSEZkARZ5KwxSU5QIdusFc6/RzSZBNA/gypzy1RCrvP CIiFeiH08jNVuDHAzzHggkhzCLYjZLKpbBYizpq5YsBXGDLbHdDChyfoV62AA1w4Aq KZ5kvbPHOP7NvOdy/i1hgKd07uI2J3a/Zk2m9Awc= Date: Thu, 24 Oct 2024 15:05:07 +0300 From: Laurent Pinchart To: Hans Verkuil Cc: Tomi Valkeinen , Mauro Carvalho Chehab , Raspberry Pi Kernel Maintenance , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Florian Fainelli , Broadcom internal kernel review list , Rob Herring , Krzysztof Kozlowski , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, Naushir Patuck , Sakari Ailus , Jacopo Mondi , Kieran Bingham Subject: Re: [PATCH v6 3/4] media: raspberrypi: Add support for RP1-CFE Message-ID: <20241024120507.GA6081@pendragon.ideasonboard.com> References: <20241003-rp1-cfe-v6-0-d6762edd98a8@ideasonboard.com> <20241003-rp1-cfe-v6-3-d6762edd98a8@ideasonboard.com> <4d9e340e-2ae7-495b-8623-0d10398e1c3d@xs4all.nl> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241024_050515_823247_EE4A118D X-CRM114-Status: GOOD ( 31.72 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Oct 24, 2024 at 01:21:43PM +0200, Hans Verkuil wrote: > On 24/10/2024 13:08, Tomi Valkeinen wrote: > > On 24/10/2024 11:20, Hans Verkuil wrote: > >> Hi Tomi, > >> > >> I know this driver is already merged, but while checking for drivers that use > >> q->max_num_buffers I stumbled on this cfe code: > >> > >> > >> > >>> +/* > >>> + * vb2 ops > >>> + */ > >>> + > >>> +static int cfe_queue_setup(struct vb2_queue *vq, unsigned int *nbuffers, > >>> +               unsigned int *nplanes, unsigned int sizes[], > >>> +               struct device *alloc_devs[]) > >>> +{ > >>> +    struct cfe_node *node = vb2_get_drv_priv(vq); > >>> +    struct cfe_device *cfe = node->cfe; > >>> +    unsigned int size = is_image_node(node) ? > >>> +                    node->vid_fmt.fmt.pix.sizeimage : > >>> +                    node->meta_fmt.fmt.meta.buffersize; > >>> + > >>> +    cfe_dbg(cfe, "%s: [%s] type:%u\n", __func__, node_desc[node->id].name, > >>> +        node->buffer_queue.type); > >>> + > >>> +    if (vq->max_num_buffers + *nbuffers < 3) > >>> +        *nbuffers = 3 - vq->max_num_buffers; > >> > >> This makes no sense: max_num_buffers is 32, unless explicitly set when vb2_queue_init > >> is called. So 32 + *nbuffers is never < 3. > >> > >> If the idea is that at least 3 buffers should be allocated by REQBUFS, then set > >> q->min_reqbufs_allocation = 3; before calling vb2_queue_init and vb2 will handle this > >> for you. > >> > >> Drivers shouldn't modify *nbuffers, except in very rare circumstances, especially > >> since the code is almost always wrong. > > > > Indeed, the code doesn't make sense. I have to say I don't know what > > was the intent here, but I think "at least 3 buffers should be > > allocated by REQBUFS" is the likely explanation. > > > > I think the hardware should work with even just a single buffer, so > > is it then fine to not set either q->min_queued_buffers nor > > q->min_reqbufs_allocation before calling vb2_queue_init()? This > > seems to result in REQBUFS giving at least two buffers. > > min_queued_buffers is really HW dependent. If not set, then > start_streaming can be called even if there are no buffers queued. Having min_queued_buffers > 1 is bad for userspace, and it's much nicer to have it set to 0. The main issue with a value of 1 is that validation of the pipeline ends up being deferred to the first QBUF if it occurs after STREAMON, and error handling is then complicated. It's not just a property of the hardware, kernel drivers can decide to work with scratch buffers if needed. In many cases, a scratch buffer allocated by the kernel could be very small, either relying on the same physical page being mapped through the IOMMU to a larger DMA space, or using a 0 stride value to write all lines to the same location. For drivers supported by libcamera, we will require min_queued_buffers <= 1 and may tighten that to == 0. Tomi, if you submit a patch, please try to target 0, and if that's too much work for now, set it to 1 at most. > If your hardware can handle that, then it's fine to not set it. > > >>> + > >>> +    if (*nplanes) { > >>> +        if (sizes[0] < size) { > >>> +            cfe_err(cfe, "sizes[0] %i < size %u\n", sizes[0], size); > >>> +            return -EINVAL; > >>> +        } > >>> +        size = sizes[0]; > >>> +    } > >>> + > >>> +    *nplanes = 1; > >>> +    sizes[0] = size; > >>> + > >>> +    return 0; > >>> +} -- Regards, Laurent Pinchart