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 417EE19066B; Mon, 28 Oct 2024 09:21:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730107281; cv=none; b=eVn9qrikx2q3I2xalcpTt1zIv//0yj9Dk1jga5BuW1L1FojhsWnPsmQwSLReXdpsX1vPDvS+pKIis2bkJhV+AgBlB6/rD8OwkJWFHRasFBBa+CuI4yGrOklCb7vT90EH7VsCsYKa3rf1APb3Y/fYxji9lsYZpBujEFru6kRYGe4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730107281; c=relaxed/simple; bh=7C8GKNsxOV7uIiousxHGq/ulpsVekLC8whXBXydwizw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=IxufgnKMCjQXLU4ifB9BYG8wFwZFpsJzXNhWEOlSzSKIFR/FCu+gVGRdHt1uZYpzEmjluSyfDFZO9JMrqV2tJ+PxNa8lC4YXJsL14rB36aZnA+jZRG3fyBc9xjnRzBqA0mh2ALYBSw6dTG2hCFpbgV4VcEG4pQ6gVIcWXeCY7mk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=YsqBksVx; arc=none smtp.client-ip=213.167.242.64 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="YsqBksVx" Received: from [192.168.88.20] (91-157-155-49.elisa-laajakaista.fi [91.157.155.49]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id BF3CA641; Mon, 28 Oct 2024 10:21:12 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1730107273; bh=7C8GKNsxOV7uIiousxHGq/ulpsVekLC8whXBXydwizw=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=YsqBksVxzjKPQo0OARBlnZZJ+oMaHz+Vb1Z5fuCUd8BdNlGSXbJwg9nepIuLMYomj Ph0q85caRSP/EN1zl9rRVtJvs2mqE6bFyHYD0OYaJwUIpnIcAHXAyBVdd0jJDld6jz bxGIuAJylg2D3SaXT4GOiwKf0xVpx55UWGmrJDXs= Message-ID: <02f05b61-08e7-45f8-8d59-f79bc20d076f@ideasonboard.com> Date: Mon, 28 Oct 2024 11:21:11 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 3/4] media: raspberrypi: Add support for RP1-CFE To: Hans Verkuil Cc: 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 , Laurent Pinchart , Sakari Ailus , Jacopo Mondi , Kieran Bingham , Mauro Carvalho Chehab , Raspberry Pi Kernel Maintenance , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Florian Fainelli , Broadcom internal kernel review list , Rob Herring , Krzysztof Kozlowski References: <20241003-rp1-cfe-v6-0-d6762edd98a8@ideasonboard.com> <20241003-rp1-cfe-v6-3-d6762edd98a8@ideasonboard.com> <4d9e340e-2ae7-495b-8623-0d10398e1c3d@xs4all.nl> Content-Language: en-US From: Tomi Valkeinen Autocrypt: addr=tomi.valkeinen@ideasonboard.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi, 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. Looking at this, the original code in the old BSP tree was, which somehow, along the long way, got turned into the above: if (vq->num_buffers + *nbuffers < 3) *nbuffers = 3 - vq->num_buffers; So... I think that is the same as "q->min_reqbufs_allocation = 3"? The distinction between min_queued_buffers and min_reqbufs_allocation, or rather the need for the latter, still escapes me. If the HW/SW requires N buffers to be queued, why would we require allocating more than N buffers? Tomi